highaltitude.log.20150219

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[00:18] <Vaizki> ok so I learned a lot about timers, pwm and interrupts this evening.. :)
[00:18] <Vaizki> good stuff...
[00:21] <Ian_> It's a deep pit once you start digging, unearthing all sorts of new goodies to clutter the brain and delay the progress of your project
[00:23] <Ian_> I have been reading up on Eagle . . . albeit slowly. Seems deceptively simple' at the moment. reality is likely to be somwhat less simple of course.
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[00:26] <Jartza> Vaizki: useful studd
[00:26] <Jartza> stuff
[00:27] <Jartza> I made poor man's burning fireplace-video with attiny
[00:27] <Vaizki> well I managed to fit together PWM output for NTX2B (timer 2) run from an interrupt handler at 50 baud (timer 1) while keeping all the standard libs happy (timer 0) and modding everything to work at 3.3V and 8MHz
[00:27] <Jartza> was really bored
[00:27] <Vaizki> for me this is an achievement :)
[00:27] <Jartza> https://www.dropbox.com/s/jhjaodsn9bkxs13/1424304373.mp4
[00:27] <Jartza> :D
[00:27] <Vaizki> ok.......
[00:28] <Jartza> Vaizki: sounds good and much more useful than my achievement :D
[00:28] <Vaizki> although I'm running from an internal oscillator here which is causing all kinds of wackiness, need to pick up 8MHz crystals
[00:28] <Jartza> tried
[00:28] <Jartza> oops
[00:29] <Vaizki> for example serial at 57600 is a joke with 8MHz internal oscillator as clock
[00:29] <Jartza> tried watching tv, but there was a channel showing burning fireplace
[00:29] <Vaizki> 9600 works well enough for debug output
[00:30] <Vaizki> btw I found a Nano which I used as an ISP programmer
[00:30] <Jartza> I have 18.432MHz crystals
[00:30] <Jartza> work nicely with uart
[00:30] <Vaizki> well you are farther away than partco for exampe :)
[00:31] <Vaizki> further, farther, fuhrer fahrer
[00:31] <Jartza> true
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[00:31] <Vaizki> 328p should be run at 8MHz on 3.3V
[00:31] <Jartza> for me partco is far away
[00:32] <Vaizki> so can't go with 16 or 18MHz crystals..
[00:32] <Jartza> mouser is closer ;)
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[00:33] <Jartza> ahh yeah, 3.3V
[00:34] <Vaizki> I have decided to abandon 5V for good. it will do me no favors :)
[00:35] <Jartza> me too
[00:39] <Jartza> but now I abandon the computer and move to bed
[00:39] <Jartza> night all
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[00:48] <Vaizki> yea me too, I got my "beacon" working fully on the prototype, need to get back to the GPS tomorrow to do the I2C code
[00:50] <Vaizki> https://dl.dropboxusercontent.com/u/367935/rtty_decode.png
[00:50] <Vaizki> wheee.. and sleep&
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[01:17] <Ian_> Night all
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[03:36] <SpacenearUS> New vehicle on the map: 03ATSAT-5 - 12http://tracker.habhub.org/#!qm=All&q=ATSAT-5
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[07:57] <SpacenearUS> New position from 03EDUPIC14 after 0310 hours silence - 12http://tracker.habhub.org/#!qm=All&q=EDUPIC14
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[08:50] <Vaizki> morning, and another noobness q.. if I wanted to filter an atmega328p pwm output so I could actually see the signal levels in a similar manner as the NTX2B, do I just need to put a capacitor across the pin and GND?
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[08:51] <SpeedEvil> Not really.
[08:52] <SpeedEvil> you don't want to do that though it might sometimes work. A resistor is needed before the capacitor for it to work well.
[08:52] <daveake> A cap is basically a short circuit to the PWM edges
[08:52] <SpeedEvil> resistor from GPIO to cap, cap to ground.
[08:52] <daveake> and you want to liit the current
[08:52] <SpeedEvil> Output signal comes from the junction
[08:52] <daveake> limit
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[08:53] <Vaizki> ok.. so if NTX2B says input resistance is 100ohm, it would be best to use a 100 ohm also in my measurement circuit?
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[08:56] <Vaizki> ok hmm.. reason I ask is I built pwm output into my tracker "sketch" because I didn't have the right resistors for a 425Hz shift. And as an educational exercise. But the PSK output is not as clean as it was with a bias voltage + resistor on a digital output (but which resulted in a 720Hz shift).
[08:57] <Vaizki> so I wanted to see how the PWM output looks but if I just straight scope it, the PWM is of course fully visible
[08:57] <RocketBoy> now here is somthing you dont see every day - https://www.youtube.com/watch?v=pD_yQZ4iNjY - nice chute deployment
[08:58] <Vaizki> so I was wondering if there's an easy way to simulate the LPF in the NTX2B to visualize how it's seeing the signal
[08:58] <Vaizki> I guess an RC filter built as a LPF would do that :)
[09:00] <daveake> lol RocketBoy
[09:00] <daveake> Yes saw that. Crowd sounded disappointed that the chute actually opened
[09:01] <Vaizki> ah the giant girandola, yes I was also expecting someone to die
[09:02] <Vaizki> no chutes here though.. https://www.youtube.com/watch?v=jbXbPHK7YXw
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[09:02] <RocketBoy> Ive seen rocket monocopters - but that was well cool - hats off to them
[09:03] <daveake> yup
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[09:22] <Vaizki> bear with me.. so if my phase correct PWM runs off a 8MHz 8bit timer without prescaler active, it's running at approx. 32kHz.. so i could just make a single order LPF with a 3dB cut off for anything say between 1kHz-10kHz and my 50 baud tx would be fine..?
[09:22] <Vaizki> (just kill me now :)
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[09:40] <SpeedEvil> Well.
[09:40] <SpeedEvil> For every doubling of frequency, the output signal of a RC lowpass halves
[09:40] <SpeedEvil> (after the knee)
[09:41] <SpeedEvil> So, you'd get at best about two halvings - a quarter of the input 32khz signal
[09:41] <SpeedEvil> If you're doing 50bps signals out - you probably want to set the lowpass to something more like 100hz.
[09:42] <SpeedEvil> And that would get you a fairlyt clean output signal with the benefit of some spectral shaping
[09:42] <Vaizki> ok.. but is that going to kill my rise time?
[09:43] <Vaizki> rise time 10-90% formula I got was 0.35/f .. with 100Hz it's 3.5ms?
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[09:51] <Vaizki> maybe this is getting a bit involved.. I will leave the PWM code to rest and just get the right resistors for a 0.21 volt shift on the TX pin
[09:51] <Vaizki> but thanks for the RC intro, makes sense now
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[09:55] <SpeedEvil> you don't want a fast rise-time.
[09:56] <Vaizki> ok.. that surprised me. do I get ringing with a fast rise then?
[09:56] <SpeedEvil> Fast risetimes - faster than - say - one third of the period of the bits - will cause excess 'spatter' - which does not help to contribute to your signal
[09:57] <SpeedEvil> As it will fall outside of the bandwidth of your receivers filter
[09:57] <Vaizki> so you are saying I should really be outputting close to a triangle wave?
[09:59] <SpeedEvil> No - sort of a squarewave, with very rounded corners
[10:01] <Vaizki> ok. well I have a working end-to-end test setup with 2 different receivers so I guess it'll be easy to try out a few filters and see what the waterfall looks like
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[10:02] <Vaizki> because right now with no filter I think there's a "bit" of that spatter that you mention
[10:03] <Vaizki> example, https://dl.dropboxusercontent.com/u/367935/rtty_decode.png
[10:03] <Vaizki> I'm assuming "spatter" is the yellow mustard all over my fldigi waterfall ;)
[10:06] <SpeedEvil> yes.
[10:07] <SpeedEvil> If you go in 1/10000th of a second from 1000300hz to 1000500hz - you don't get the simple transition from 300-500hz - noise spatters +-10khz or so.
[10:10] <Vaizki> so slower rise time will mean less spatter on the outside of the FSK edges but a bit more inside them?
[10:11] <SpeedEvil> yes.
[10:11] <SpeedEvil> You only care about signal that falls into the passband of the reciever, and is understood by the recieving modem
[10:12] <SpeedEvil> slowing the transitions can boost this.
[10:12] <SpeedEvil> Going too far of course doesn't help
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[10:18] <Vaizki> nice. very very helpful.
[10:19] <Vaizki> that basically means even if I dump PWM, my tx would benefit from a LPF RC filter
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[10:20] <Vaizki> or maybe that's done by NTX2B for me?
[10:20] <infaddict> morning
[10:20] <Vaizki> their datasheet doesn't say what the LPF is (or I'm blind)..
[10:20] <Vaizki> morning infaddict
[10:22] <Vaizki> then again they say "data rates up to 10kbps" so their LPF can't be even close to what would be optimal
[10:22] <Vaizki> ok I was blind. The NTX2B in standard form incorporates a low pass filter with a 5kHz nominal bandwidth
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[10:23] <infaddict> I've made some great progress using UBX protocol with my uBlox. Much faster than string parsing with NMEA. I now poll for a status update every X seconds and works a treat.
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[10:24] <infaddict> Need to work some more on a few of the bitfields coming back tho as not making sense right now
[10:24] <SpeedEvil> Vaizki: basically yes - the maximum datarate tells you abou the filter
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[10:24] <Vaizki> infaddict, you may want to read the morning's log, I was given a primer in filtering you might find interesting
[10:25] <infaddict> ah sure will do that thanks Vaizki
[10:25] <Vaizki> SpeedEvil, so if they have a 10kbps data rate and 5kHz filter, they must refer to modes with more than one bit per symbol?
[10:26] <SpeedEvil> Perhaps.
[10:26] <SpeedEvil> I haven't read the datasheet in detail
[10:26] <SpeedEvil> s/in detail//
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[12:06] <LunarWork> hello
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[12:06] <Guest50676> Has anyone ever had problems with parachute deployment
[12:07] <edmoore> yes
[12:07] <edmoore> many people have
[12:07] <edmoore> but it doesn't happen much now as there are fairly straightforward ways of making it likely to work
[12:07] <lz1dev> none of them survived to tell the tale
[12:07] <edmoore> also that
[12:07] <edmoore> survivor bias
[12:08] <Guest50676> what are the best methods of deployment?
[12:08] <edmoore> not deploying it
[12:08] <edmoore> that's the best way
[12:08] <edmoore> have it already deployed in-line between payload and balloon
[12:08] <edmoore> play with active deployment if you know what you're doing but don't if you don't
[12:09] <Guest50676> so therefore when the balloon bursts its already there?
[12:09] <edmoore> http://blog.jgc.org/2011/03/gaga-1-stack.html
[12:09] <edmoore> yes
[12:09] <edmoore> that's a nice diagram someone drew after we talked them through it
[12:11] <Guest50676> i think i have spoken to you before, but what if im looking to make it under 2m in height
[12:12] <edmoore> oh
[12:12] <edmoore> no need for a chute
[12:12] <edmoore> it'll be so light that the remains of balloon will provide plenty of drag
[12:13] <Guest50676> do you know the sort of energy it might be hitting the ground with?
[12:14] <edmoore> we can work out a number
[12:14] <Guest50676> just want to to be safe and im doing it for uni so i have to justify it
[12:14] <edmoore> let's say it has a mass of 50g
[12:14] <edmoore> that's 0.05kg
[12:14] <edmoore> let's say it lands at a velocity of 5m/s
[12:14] <edmoore> kinetic energy is 0.5*mass*velocity*velocity
[12:15] <edmoore> = 0.5*0.05*5*5 = 0.625 joules
[12:15] <infaddict> out of interest, whats the reason for the long 8m of cord between chute and payload?
[12:16] <infaddict> why not 4m like chute to balloon?
[12:16] <infaddict> or shorter
[12:16] <edmoore> because then if the balloon remains flop down they don't hit the payload
[12:17] <edmoore> but don't assume that people who did it before had a mystical connection to the wisdom of the ancients
[12:17] <edmoore> it's just a way to do it
[12:17] <edmoore> not The way
[12:17] <Guest50676> our balloon is going to be about 500g so it isnt too light. but it is under the 2m limit
[12:17] <Guest50676> so its heavy and small
[12:18] <edmoore> that's a very very heavy balloon to stay under 2m
[12:18] <edmoore> surprising
[12:19] <Guest50676> well we are reading humidity temperature solar flux altitude, quite a few things
[12:19] <craag> is that under 2m at launch, or burst?
[12:19] <Guest50676> burst
[12:19] <craag> wow ok
[12:19] <Guest50676> 1.6m balloon
[12:19] <jonsowman> which balloon is it?
[12:19] <Guest50676> at burst
[12:19] <craag> pawan 100g?
[12:19] <Guest50676> thats the one
[12:20] <edmoore> it's nopt 500g
[12:20] <edmoore> the clue is in the name
[12:20] <Guest50676> i mean the whole balloon and payload
[12:20] <jonsowman> right ok
[12:20] <craag> So burst at ~6km
[12:20] <jonsowman> that makes a lot more sense
[12:20] <craag> for 5 m/s ascent
[12:20] <mattbrejza> LAB
[12:21] <Guest50676> where do you have that information from craag?
[12:21] <craag> http://habhub.org/calc/
[12:22] <mfa298> 500g might be a bit heavy to rely on the balloon remanants to slow it down.
[12:22] <edmoore> yes i agree with that
[12:22] <edmoore> you'll want a chute
[12:22] <edmoore> that will make doing this in 2m harder
[12:23] <Vaizki> so is it ok to transmit 2 different sentences alternatively?
[12:23] <Vaizki> from 1 payload?
[12:23] <craag> Vaizki: Yep, just add both to the payload doc
[12:23] <Vaizki> ok great
[12:24] <mfa298> Guest50676: also if you're UK based and you're trying to fit inside the 2m rule, that's the complete system, Payload + balloon for the whole flight, If the box is 20cm high, with a 1.6m balloon and 20cm of cord between the balloon and payload that's your 2m used (and you'll also want 16cm out the bottom for the antenna which will take you out of the 2m sphere)
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[12:25] <Guest50676> yes mfa298 its a little tight
[12:25] <Guest50676> so i dont really know where to fit in a chute
[12:25] <craag> Also the balloon will be very taut, and might be a bit fragile at launch.
[12:26] <Geoff-G8DHE-M> nor are you likely to get 5m/s ascent rate, but if you drop below that then a float becomes possibel
[12:27] <fsphil> the met office put the chute into the balloon
[12:27] <Guest50676> we are looking to try and reach 10700m and starting at a 1m balloon diameter
[12:28] <Geoff-G8DHE-M> what is the payload weight alone ?
[12:28] <Guest50676> 400g
[12:29] <Geoff-G8DHE-M> you can put the figures in as well but that will be 2m/s ascent rate
[12:30] <craag> For 5m/s ascent, you'll only get 6km
[12:31] <craag> Your only option IMO, is to reduce payload weight.
[12:31] <Guest50676> we were looking at 3.75m/s
[12:31] <Guest50676> for ascent rate
[12:31] <craag> Only reduce the ascent rate if you're open to the possibility of it floating.
[12:31] <Geoff-G8DHE-M> umm 6km ? i grt 4.4km
[12:32] <Guest50676> as do i
[12:32] <craag> Geoff-G8DHE-M: Put in 4.5, it'll find a solution at 5.07
[12:35] <Geoff-G8DHE-M> All tends to say its critical and difficult to predict ...
[12:35] <Guest50676> so if you wanted to measure humidity, temperature, solar flux, altitude, lat and long how would you keep the payload low?
[12:36] <craag> solar flux?
[12:37] <Guest50676> power per unit area i believe
[12:37] <craag> How are you doing that directly under a mostly-opaque sphere?
[12:38] <craag> The electronics for that should easily be <100g. Could be <40g if you made your own pcb.
[12:40] <Guest50676> even if you have to transmit it all aswell?
[12:40] <Guest50676> What battery would weigh that little?
[12:41] <craag> Energizer Lithium Cells
[12:41] <craag> could be AAAs
[12:42] <Guest50676> are lithium batteries not a little volatile?
[12:42] <craag> These are not lithium-ion or lithium-polymer
[12:42] <craag> Very differnt
[12:42] <craag> http://data.energizer.com/PDFs/l91.pdf
[12:42] <craag> Non-rechargeable
[12:43] <craag> Slightly more capacity than alkaline
[12:43] <craag> but vitally - very good performance in very low temperture
[12:43] <daveake> and lighter too
[12:43] <craag> Also AAA: http://data.energizer.com/PDFs/l92.pdf
[12:44] <craag> 7.6g for the AAA
[12:44] <craag> 14.5g for AA
[12:44] <craag> And you can use a voltage step-up to run a 3.3V payload off only 1 or 2.
[12:45] <Geoff-G8DHE-M> Something like this which is jededu design http://imgur.com/tRS1uT0
[12:46] <craag> Yep that's a good example of a custom PCB (albeit sensor-less)
[12:47] <craag> But even if you're cobbling it together with stripboard
[12:47] <craag> There's the 'Lipower boost converter' that I used on my first payload.
[12:47] <craag> https://www.philcrump.co.uk/images/d/d0/FlightPrototype_CRAAG1.JPG
[12:48] <craag> more info: https://www.philcrump.co.uk/CRAAG1
[12:49] <craag> Used a single AAA in the end - gave about 4.5 hours iirc
[12:52] <Guest50676> iirc?
[12:52] <craag> (if i recall correctly)
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[12:53] <craag> btw: DO NOT USE RFM22
[12:54] <craag> Yes, it's nice and light - but go with the ntx2b, will save your soul :)
[12:56] <fsphil> yes do that ^
[12:56] Action: fsphil lost a payload due to rfm22b failure
[12:57] <daveake> I nearly did, but it came back to life in time
[12:57] <daveake> ditto Steve
[12:57] <fsphil> to be fair I've also lost a payload that used an NTX2, though in both those cases I know the general area they landed
[12:58] <fsphil> * all but 1 intentionally lost
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[13:16] <Guest50676> would a arduino micro board work?
[13:16] <edmoore> time was (spits out tabaccey) that a guy would often lose his payload in the dang sea
[13:17] <edmoore> Guest50676, yes
[13:17] <Guest50676> it would have enough pins and things?
[13:18] <edmoore> depends on what you want to do
[13:18] <Geoff-G8DHE> would depend on how the sensors are connected etc.
[13:18] <Geoff-G8DHE> SPI or I2C can handle quite a few ..
[13:28] <Guest50676> is there way to calculate the gain of a quarter wave antenna?
[13:28] <Laurenceb> http://koti.kapsi.fi/jpa/stuff/pix/sigrok_swo.png
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[13:29] <Laurenceb> swo plugin for sigrok
[13:29] <craag> Guest50676: It's 2.15dBi nomimally for a 1/4 wave
[13:30] <craag> Although really it's going to change a lot as the payload swigns around
[13:30] <craag> *especially* when it's up against the balloon like that.
[13:32] <Guest50676> so theres no real set equation?
[13:33] <craag> Not really as we don't know much about the sensitivity of dlfldigi - and it depends a lot on how it's set up
[13:33] <SpacenearUS> New vehicle on the map: 03DIPERK1 - 12http://tracker.habhub.org/#!qm=All&q=DIPERK1
[13:34] <craag> But we do know: with a 10mW transmitter, and a 1/4 wave antenna, a 1/4wave antenna on the ground, and pretty much any ssb radio with audio piped into dlfldigi - it'll work fine at 50 baud.
[13:34] <craag> The low baudrate gives us a massive link budget
[13:35] <craag> But stuff like the payload antenna swinging around, and local interference can mess with that, unpredictably.
[13:35] <craag> On average though - it works :)
[13:35] <craag> With a little preparation - it can be very reliable.
[13:38] <Guest50676> would it be more reliable with a yagi on the ground?
[13:38] <edmoore> no
[13:39] <edmoore> yagis need to be kept pointed at the payload
[13:39] <Guest50676> and quarter waves are omni directional?
[13:40] <Geoff-G8DHE> Yes, you will get an improvment on the ground is you use a co-linear aerial again omni-directional
[13:41] <Geoff-G8DHE> but they are larger and need to be mounted up in the clear, not really for mobile tracking
[13:42] <Geoff-G8DHE> A small Yagi comes in if you have to DF a payload over the last few miles.
[13:42] <craag> A small magmount like this works well for chasecar tracking:
[13:42] <craag> http://cpc.farnell.com/watson/wsm-270/wsm-270-mini-mag-antenna/dp/IT44456
[13:42] <craag> Yes it's omnidirectional
[13:43] <craag> Although it's a lot better perpendicular to the element, than at an angle towards the end of the element.
[13:43] <craag> Hence why it swinging around can make things a little more difficult
[13:44] <Guest50676> what about if you arent chasing it but staying stationary until it lands
[13:45] <craag> If you're planning to recover it, it's a lot better to be as nearby as possible when it lands.
[13:46] <Guest50676> why is that? if you're trasmitting the position once landed wont it be the same?
[13:46] <Reb-SM0ULC> Guest50676: btw, get a real irc-client and prepare to hang around. :) http://xchat.org/ or http://www.mirc.com/
[13:46] <craag> But answering your question - that little antenna can work well even from a hundred miles away or so as long as you have line-of-sight to the payload.
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[13:47] <craag> The closer to the landing you are, the longer you'll maintain line-of-sight
[13:47] <craag> So you get a later position.
[13:48] <craag> Once it's on the ground, you'll need to be within at least a mile or so to be able to receive it.
[13:48] <Guest50676> even if you send an SMS message?
[13:48] <craag> SMS is a good backup
[13:48] <craag> But if it lands in a ditch..
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[13:48] <craag> the SMS won't send, and you'll need to be within 50 yards or so before you can hear it on the radio.
[13:49] <craag> (nearly worst-case)
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[13:49] <craag> If the last position you had was at 2000m or so on the way down, you'll be searching a very large area
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[13:51] <craag> Time for me to get back to work :) Have a read of this: http://www.daveakerman.com/?p=1732
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[14:00] <daveake> I think that overloaded him
[14:02] <cm13g09> well daveake it is a bit of an essay!
[14:05] <Vaizki> well that was a lot of fun finding buffer overruns in my code..
[14:08] <Jartza> http://labs.rakettitiede.com/?p=206
[14:10] <UpuWork> Pair of lora trackers https://dl.dropboxusercontent.com/u/63720513/Images/uAvaNut/uAvanut_lora.jpg
[14:11] <edmoore> gps reception ok?
[14:11] <craag> very nice
[14:12] <craag> pyro mosfet too?
[14:12] <Vaizki> cool
[14:13] <Geoff-G8DHE> Nice
[14:13] <Vaizki> looks like pyro with external battery
[14:13] <craag> And cute little led indicator diagrams :)
[14:14] <UpuWork> yep edmoore
[14:14] <UpuWork> why do you ask ?
[14:14] <edmoore> small patch without ground plane
[14:14] <infaddict> !wiki coding errors
[14:15] <SpacenearUS> 03infaddict: Wiki page 03common_coding_errors_payload_testing - 12http://ukhas.org.uk/guides:common_coding_errors_payload_testing
[14:15] <UpuWork> (only soldered down on 2 points in case something is wrong with the board so I can get them back off as they are expensive)
[14:15] <UpuWork> design for that apparently
[14:15] <UpuWork> well
[14:15] <UpuWork> work with that
[14:15] <UpuWork> yes pyro
[14:16] <Geoff-G8DHE> On internal battery or the external one or just the FET itself ?
[14:16] <Vaizki> infaddict, did you change to the recoon i2c library btw?
[14:16] <infaddict> nope i didnt, just did a mod BUFFER_LENGTH and ended xmit when i detected that
[14:17] <infaddict> i.e. every 32 bytes
[14:17] <UpuWork> if you jumper where it says OBB (on board battery) it will use that to fire whatever you have wired to PYRO
[14:17] <UpuWork> however
[14:17] <UpuWork> probably not recommended for nichrome :)
[14:17] <Geoff-G8DHE> :)
[14:18] <Vaizki> infaddict, ok.. I have everything working except GPS so that's next
[14:19] <infaddict> ok, happy to share my code once i've tidied it up if you want it. i am using uBlox 8 series with i2c.
[14:19] <infaddict> just sat in my garden for 10 mins to check gps lock on
[14:20] <infaddict> seems to take longer to lock in airborne <1g mode
[14:21] <Vaizki> I have been fuzzing my NTX2B rtty code to make sure it works with weird kinds of input
[14:21] <Vaizki> I definitely don't want the tracker to crash
[14:21] <infaddict> yer seems we've attacked it in opposite directions, which might be mutually beneficial. my radio kit still not arrived so i've been focusing on gps.
[14:22] <Vaizki> I am running NTX2B off the atmega328p timer 1 using interrupts at baud rate
[14:23] <Vaizki> I have not tested it with 5V and 16MHz yet but works at 3.3V and 8MHz at least
[14:27] <infaddict> yep i have interrupt code ready to go too when i get a receiver
[14:27] <infaddict> also using timer1
[14:27] <infaddict> at 1024 prescale
[14:29] <Vaizki> same here, there was an example somewhere that I heavily modified
[14:30] <infaddict> you using 50baud?
[14:31] <Vaizki> seems to work with 5,7,8 data bits, 1 or 2 stop bits, even/odd parity, baud rates 50, 300 and 1200
[14:31] <Vaizki> yes I use 50baud, 7 data bits, no parity, 2 stop bits
[14:31] <Vaizki> but I implemented support for everything while I was revising...
[14:32] <infaddict> yer the baud just feeds into timing equation so easy to make dynamic
[14:32] <Vaizki> well by "works" I mean I can receive it with radios and decode :)
[14:32] <infaddict> thats a great start!
[14:33] <Vaizki> I could cut down on memory use or optimize a bit but seems to be no need to really
[14:33] <Vaizki> how long does it take to fetch a position from the ublox over i2c?
[14:33] <infaddict> yer i'm worried about RAM
[14:34] <Vaizki> I am declaring a lot of stuff as static
[14:34] <infaddict> with large buffers it runs out quick
[14:34] <infaddict> i only have 2k
[14:35] <mattbrejza> declaring stuff static doesnt do anything as far as ram usage is concerned
[14:36] <Vaizki> umm they shouldn't be off the stack if they are static?
[14:36] <infaddict> so that could increase ram
[14:36] <infaddict> as no garbage collection
[14:36] <Vaizki> Global variables use 617 bytes (30%) of dynamic memory, leaving 1,431 bytes for local variables. Maximum is 2,048 bytes.
[14:36] <Vaizki> my current situation
[14:36] <infaddict> by ref / by val is more important
[14:37] <infaddict> just including libraries like wire eat up a huge chunk
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[14:37] <Vaizki> I assume static variables are counted in the "Global variables"?
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[14:37] <mattbrejza> by static you mean variables at the top of the program?
[14:37] <mattbrejza> global ones?
[14:37] <infaddict> not sure depends how u are measuring your RAM. i am using daveake's code.
[14:38] <mattbrejza> (also lol arduino libraries)
[14:38] <Vaizki> mattbrejza, no I mean variables declared static anywhere
[14:38] <Vaizki> and yes they seem to be counted towards that global variable size
[14:39] <mattbrejza> hmm didnt realise you can static variables inside functions
[14:39] <mattbrejza> thats kinda horrible
[14:39] <Vaizki> no it's not, it's perfect
[14:39] <infaddict> you might want a counter for example
[14:39] <infaddict> to increment
[14:40] <infaddict> many reasons why
[14:40] <mattbrejza> still not a fan :P
[14:40] <mattbrejza> i guess its tidier than writing it global at the top of the file
[14:40] <daveake> yup
[14:40] <Vaizki> yea it's the same thing except for scoping
[14:40] <daveake> e.g. sentence counter could go inside the riutine that builds the sentence
[14:40] <infaddict> much safer for scope
[14:40] <daveake> assuming ofc it's not needed elsewhere
[14:42] <Vaizki> like my RTTY transmit function grabs the string given by the caller and strncpy it to a static declared buffer, then starts of the xmit with a pointer to the head of that
[14:42] <gonzo_> static vars will be in the vars area, allocated by the linker, rather than on the stack
[14:42] <Vaizki> so the buffer is not visible outside that func
[14:42] <infaddict> gonzo_: sure but does that save any RAM?
[14:42] <infaddict> u save adding a number to the stack, so its more effecient execution wise, but maybe not for memory
[14:42] <gonzo_> nope, it is in ram and will always exist
[14:43] <infaddict> yep
[14:43] <gonzo_> so may as well be global, apart from limiting the scope
[14:43] <infaddict> indeed
[14:43] <fsphil> so easy to abuse
[14:43] <gonzo_> but in a prog as small as a basic tracker, I would question the need to even do that
[14:43] <fsphil> like goto
[14:44] <Vaizki> it's not abuse
[14:44] <gonzo_> in a small processor, with limited memory, I prefer to have things globval, so you can see what you are using
[14:44] <Vaizki> indeed
[14:44] <fsphil> I've seen programs that keep state all spread out in static variables
[14:45] <fsphil> one of which I had to convert to be thread safe
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[14:45] <fsphil> that was many many years ago and it still haunts me :)
[14:45] Action: daveake senses that fsphil had some fun with that
[14:45] <Vaizki> well my ISR has everything static for example, I don't see why not
[14:45] <Vaizki> just feels right not to allocate memory dynamically for an ISR.. :P
[14:45] <fsphil> that's perfectly fine
[14:45] <fsphil> I do that myself
[14:45] <infaddict> you can also move some stuff to PROGMEM
[14:45] <Vaizki> even if it' from a stack
[14:45] <infaddict> like constants
[14:45] <infaddict> or strings
[14:46] <fsphil> my aprs and rtty interrupts all have statics
[14:46] <infaddict> https://learn.adafruit.com/memories-of-an-arduino/optimizing-sram
[14:46] <gonzo_> I would not be comfortabe with anythiung dynamic in a small embedded system
[14:47] <fsphil> I remember when I first started using AVRs, wondering where malloc() was
[14:47] <daveake> hah
[14:47] <infaddict> quote: "Global and Static variables are the first things loaded into SRAM. They push the start of the heap upward toward the stack and they will occupy this space for all eternity."
[14:47] <fsphil> I think there is a malloc() there now
[14:48] <gonzo_> the embedded 386 stuff I used to work on, it did have a malloc and people tried using it
[14:48] <mattbrejza> well there must be for arduino to work?
[14:48] <gonzo_> but by that time it was just a stub, I took the workings out
[14:48] <mattbrejza> with c++ and all
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[14:54] <fsphil> avr-libc has always had malloc(). I probably did something stupid
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[14:58] <Vaizki> so what i2c/twi library should I look at? not sure I need to write my own even though it doesn't seem impossible to do that either..
[14:59] <Vaizki> bunch of TW* registers and seems to have a dedicated clock too
[15:00] <Vaizki> and no I don't need the C++ sauce on it ;)
[15:00] <edmoore> didn't know avr-libc had malloc
[15:00] <edmoore> probably chose to unsee that
[15:00] <Vaizki> as said, c++ wouldn't work without it?
[15:01] <Vaizki> well not sure how c++ the arduino stuff really si
[15:02] <edmoore> c++ should work fine without malloc
[15:03] <edmoore> in as much as you don't need dynamic memory allocation to write C or C++
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[15:07] <Vaizki> ok well I'm not that versed in how C++ does some of it's magic beyond the syntactic sugar but I assumed malloc() would be involved implicitly
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[15:16] <edmoore> new i think probably does the same thing as malloc under the hood
[15:16] <edmoore> but basically i'm saying you can do statically managed c++ and c quite happily
[15:16] <edmoore> some coding standards (for embedded) require it
[15:16] <infaddict> Vaizki: start with the basic wire library to get your code working. only thing to beware is the 32 byte buffer on sending.
[15:18] <infaddict> only commands you need are: Wire.begin, Wire.requestFrom, Wire.read, Wire.available, Wire.beginTransmission and Wire.endTransmission
[15:18] <infaddict> oh and Wire.write too
[15:19] <infaddict> its the Wire.write where the buffer slipup can happen
[15:20] <infaddict> i'm sticking with that for now unless i hit a big problem or RAM issue
[15:20] <infaddict> rather than re-invent the wheel
[15:21] <infaddict> i now have code for radio, gps, temperature, voltage and SD card in separate sketches. next job is to combine and see if i have enough room. ready to ditch SD or move to new SD library.
[15:21] <Vaizki> I don't want to have any Arduino dependencies if possible...
[15:22] <infaddict> Wire is just a wrapper to Twi. You can make your own copies of them if you want to.
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[15:24] <infaddict> there are many other libraries out there created by people. just google avr i2c library. not had any experiences of them so cant comment or recommend. maybe others have.
[15:29] <infaddict> Silly code question time. Why does variable "out" contain 54.9901 instead of 54.9901393?
[15:29] <infaddict> long lat = 549901393;
[15:29] <infaddict> const float factor = 0.0000001;
[15:29] <infaddict> float out;
[15:29] <infaddict> out = lat * factor;
[15:29] <infaddict> even using (float) casts i get same thing
[15:29] <infaddict> i thought floats had 7 precision after decimal
[15:30] <Laurenceb> sheet
[15:30] <Laurenceb> this is nice http://www.semtech.com/wireless-rf/rf-transceivers/sx1257/
[15:30] <Laurenceb> pity no 434mhz
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[15:34] <adamgreig> infaddict: uhm
[15:34] <pc1pcl> http://forum.arduino.cc/index.php?topic=121746.0
[15:34] <adamgreig> floats are binary not decimal is your main problem
[15:34] <adamgreig> e.g. try putting 0.1 in a float
[15:34] <daveake> 6-7 digits total
[15:35] <daveake> not after dp
[15:35] <adamgreig> http://www.h-schmidt.net/FloatConverter/IEEE754.html is quite nice (from that arduino forum link)
[15:35] <pc1pcl> a float is a nice idea, but the underlying hardware is much more 'interesting' than the theory.
[15:35] <adamgreig> also yes your arduino doesn't even have a floating point unit
[15:35] <daveake> and don't try double - those are no more precise
[15:35] <adamgreig> are doubles implemented as floats on arduino? gross
[15:36] <daveake> yup
[15:36] <infaddict> yep float = double on arduino
[15:36] <adamgreig> you'd think doing both in software they could do longer ones
[15:36] <adamgreig> anyway
[15:36] <daveake> that would be too sensible
[15:36] <adamgreig> just divide it by 1000000 integer
[15:36] <pc1pcl> integer maths
[15:36] <adamgreig> and take %1000000 to get remainder
[15:36] <adamgreig> or just transmit the microdegrees tbh
[15:36] <adamgreig> much easier
[15:36] <mattbrejza> i wonder how many cycles %10000000 takes on an avr
[15:36] <Vaizki> eep I've never used a float in Arduino
[15:37] <infaddict> so the uBlox returns a long lat/long with scaling of 0e-7...
[15:37] <infaddict> thats what i am dealing with
[15:37] <adamgreig> yea
[15:37] <adamgreig> longs are ints
[15:37] <adamgreig> it returns "microdegrees" iirc
[15:37] <adamgreig> ie *10^-6
[15:38] <adamgreig> unless you're actually doing maths with the positions
[15:38] <pc1pcl> do you need to really do any calculations, or can you fake it with string manipulation?
[15:38] <adamgreig> you can just transmit the microdegrees
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[15:38] <adamgreig> you don't even need to fake it
[15:38] <adamgreig> just transmit the integer
[15:38] <infaddict> mmm good point, i am not doing maths just wanted to get it to a nice looking degrees
[15:38] <adamgreig> snprintf(s, n, "%lu", my_microdegrees)
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[15:38] <infaddict> so will habhub accept the number at this scaling?
[15:39] <adamgreig> yes (habhub accepts any scaling)
[15:39] <adamgreig> (your payload doc tells habitat what to scale by)
[15:39] <infaddict> ok thx guys some good ideas
[15:39] <Vaizki> also you save a byte on the . character!
[15:39] <Vaizki> that's another 20ms saved
[15:39] <adamgreig> you might also consider truncating a little
[15:39] <Vaizki> 40ms total for 2 lat+lon
[15:40] <adamgreig> probably don't need to transmit at 1 microdegree precision
[15:40] <infaddict> yer i doubt i need all those to the right of the dp
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[15:40] <infaddict> what is usual? 4 after the decimal point?
[15:40] <infaddict> e.g. 54.1234
[15:40] <infaddict> or more?
[15:40] <daveake> 200ms not 20
[15:41] <Vaizki> yes sorry 200ms per character
[15:41] <adamgreig> 1 microdegree is 11cm longitude along the equator (smaller as you move north/south) and 79mm latitude
[15:41] <adamgreig> so yes, you probably do not need them all
[15:42] <infaddict> so could do integer division (e.g. / 1000) to chop some off
[15:42] <craag> 5 after dp is a good point I think
[15:42] <craag> gets you down to ~1m
[15:43] <pc1pcl> or shorten the string by 3?
[15:43] <mattbrejza> tahts asking for trouble though
[15:43] <infaddict> its not a string at present. UBX is binary.
[15:43] <craag> which is more resolution than accuracy most of the time anyway - but allows you to take a visual average easily.
[15:43] <infaddict> so it comes in as a long
[15:44] <pc1pcl> oh, yes, you're talking UBX to it.
[15:44] <infaddict> well, 4 chars actually, that I combine to a long
[15:44] <Vaizki> 4 bytes
[15:44] <infaddict> yep
[15:44] <Vaizki> just send the bytes!
[15:44] <Vaizki> :)
[15:44] <Vaizki> ok so you'd need 8bits rtty for that..
[15:45] <craag> start with ascii rtty
[15:45] <craag> then some of us are working on native binary formats ;)
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[15:53] <Reb-SM0ULC> infaddict: thera have been positionsreports with 10-12 decimels.. :)
[15:53] <infaddict> ;-)
[15:54] <Reb-SM0ULC> infaddict: some differ the precision according to height, > x km few digits, < more etc
[15:55] <infaddict> good point, guess you might want more accuracy when finding it on the ground
[15:55] <infaddict> assuming you are getting good altitude readings
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[16:09] <Reb-SM0ULC> infaddict: if they are not okay they are usually possible to detecet
[16:14] <edmoore> true: https://twitter.com/ambassadorcio/status/561992427717021697
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[16:33] <Reb-SM0ULC> edmoore: :)
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[16:36] <infaddict> Someone mentioned earlier that habitat could deal with any scaling of lat/long. when i create a payload i only see dd.dddd or ddmm.mmmm in the coordinate options.
[16:36] <adamgreig> you want dd.dddd and then you can tell it to scale your lts and lngs by 1e-6
[16:36] <infaddict> the suggestion was to give it something like 5412345 and it would know that means 54.12345
[16:37] Nick change: Guest33333 -> Kalcharr
[16:37] <infaddict> ok thx adamgreig - how do i tell it to scale?
[16:37] <infaddict> i cant see that but clearly missing something
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[16:37] <Kalcharr> Hello
[16:38] <edmoore> hi
[16:38] <Kalcharr> Is anyone available to help me out with a problem im having with the MAX-M8C Pico Breakout with Chip Antenna
[16:39] <Kalcharr> I'm trying to access it over serial from a Raspberry Pi but im getting nothing back from it.
[16:39] <edmoore> ok, does it give any outward signs of life?
[16:39] <edmoore> do you have a multimeter to confirm that it's getting 3.3V at the vcc pin and there is gnd continuity?
[16:40] <adamgreig> infaddict: it's right thereif you use the sentence wizard (recommended)
[16:40] <adamgreig> just has a "scale this?" tickbox
[16:40] <adamgreig> if you tick it, it presents options to do all sorts of scaling, with exmaples of what will happen
[16:40] <infaddict> ah right, i am entering fields manually and no option to scale
[16:40] <adamgreig> well it's still there ifyou do it manually
[16:41] <adamgreig> you just need to add a 'post parse filter'
[16:41] <adamgreig> it's a bit more fiddly
[16:41] <adamgreig> I recommend using the wizard
[16:41] <infaddict> not for me. sentence editor shows no scaling options. I get field name, type and then dd.dddd
[16:41] <adamgreig> ^^
[16:41] <infaddict> i will try the wizard tho thx
[16:42] <Kalcharr> edmoore: It is getting the voltage, There dont seem to be anything that could show signs of life on it
[16:42] <infaddict> ideally it should let you edit it later tho, not have to redo the whole thing with the wizard again
[16:42] <adamgreig> it.. does
[16:42] <edmoore> ok, what are you using to monitor the serial port Kalcharr?
[16:42] <adamgreig> you can copy existing ones, make new ones based on existing ones, etc
[16:42] <Kalcharr> cutecom
[16:42] <adamgreig> 'edit' is always "make a new one, starting from existing", it's create-only in that sense
[16:43] <adamgreig> but it's the same effect
[16:43] <edmoore> Kalcharr, sorry if this is insultingly obvious, but do you definitely have Tx and Rx connected up the right way round?
[16:43] <edmoore> the Pi's Tx should connect the the GPS's Rx and vice-versa
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[16:44] <Kalcharr> edmoore: No Problem, I've tried both configurations as a troubleshooting measure
[16:45] <Kalcharr> edmoore: They are currently connected correctly now
[16:45] <edmoore> i presume you have tried different cutecom settings to make sure you've the right port etc
[16:45] <edmoore> do you have an oscilloscope?
[16:45] <Kalcharr> no not with me
[16:46] <Kalcharr> I've messed around with the baud but nothing else
[16:46] <edmoore> hmm, well if you can get to one i'd look to see if the ublox is actually sending anything
[16:47] <edmoore> a multimeter will probably indicate it too sort of
[16:47] <edmoore> it should be mostly 3.3V with occassional blips to less
[16:47] <Kalcharr> yea I got this module: http://ava.upuaut.net/store/index.php?route=product/product&path=59_60&product_id=52
[16:48] <Kalcharr> and there doesnt seem to be any life in it.
[16:48] <edmoore> i've heard of that store
[16:48] <edmoore> very disreputable seller
[16:48] <edmoore> stay away
[16:49] <Kalcharr> shit, If I'd known.
[16:49] <edmoore> i'm joking!
[16:50] <edmoore> it's Upu
[16:50] <edmoore> in this channel
[16:50] <edmoore> he's very good
[16:50] <Kalcharr> :p
[16:50] <Kalcharr> thats how i got to this IRC :p
[16:50] <Laurenceb> trollaltitude
[16:50] <UpuWork> lol
[16:50] Action: UpuWork slaps edmoore
[16:50] <UpuWork> how do you have it wired Kalcharr ?
[16:51] <Kalcharr> gps hooked into breadboard and then cables running from pi GPIO to breadboard
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[16:52] <edmoore> take a piccy maybe
[16:52] <edmoore> then call me maybe
[16:52] <UpuWork> is it going to the Pi's serial port ?
[16:52] <UpuWork> I have to shoot in a sec but try this :
[16:52] <Kalcharr> yep going to the TX and RX
[16:53] <UpuWork> run sudo raspi-config
[16:53] <UpuWork> Advanced Options --> Disable Serial shell
[16:53] <UpuWork> reboot
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[16:53] <UpuWork> type : minicom -b 9600 -o -D /dev/ttyAMA0
[16:53] <Kalcharr> I've disabled that as I was working with an XBee module erlier over serial
[16:53] <UpuWork> see what comes out
[16:53] <Kalcharr> So i know the serial connection works with other modules
[16:53] <UpuWork> switch RX and TX if nothing I'll be back in about 45 mins
[16:54] <UpuWork> its likely to be faulty but I'm not ruling it out
[16:54] <UpuWork> back shortly
[16:54] <Kalcharr> no problem
[16:55] <Kalcharr> UpuWork: Nothing back from Minicom
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[17:28] <Upu> Back
[17:28] <Upu> what was your order number please ?
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[17:35] <Kalchar> Upu: I'll grab it now
[17:36] <Kalchar> Upu: 2737
[17:37] <Upu> does the other one work ?
[17:38] <Upu> and you get no output at all ?
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[17:39] <Kalchar> Upu: No nothing at all from either of them, I can see an increase in current draw when i connect them up but nothign from minicom or cgps
[17:39] <Upu> ok its very unlikely there is a fault with both modules
[17:39] <Kalchar> thats what i was thinking
[17:39] <Upu> can you task a picture of your set up pls ?
[17:39] <daveake> Remove the module, short rx and tx on the breadboard, and see if you have an echo
[17:40] <Kalchar> There is no current draw from the chip antenna module
[17:40] <Upu> it won't be much
[17:40] <Upu> 20mA
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[17:47] <Kalchar> Fixed it, The modules werent making proper contact with the pins, they needed to be tilted a bit nore for full contact.
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[17:48] <edmoore> but you said you measured continuity on them when i asked
[17:48] <edmoore> oh well
[17:49] <Kalchar> sorry, the TX RX pins werent makign connection
[17:49] <Kalchar> the power pins were
[17:49] <edmoore> oh well. one of the joys of breadboard
[17:49] <edmoore> glad it's working
[17:50] <daveake> Please, someone uninvent breadboard
[17:50] <Kalchar> haha
[17:52] <daveake> If I had a penny for every breadboard-related issue that has cropped up in this channel, I'd have enough to buy a piece of veroboard for the next guy.
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[18:00] <SpacenearUS> New position from 03KF5PGW-1 after 0316 hours silence - 12http://tracker.habhub.org/#!qm=All&q=KF5PGW-1
[18:06] <SpacenearUS> New position from 03PI_SKY_PLUS after 036 days silence - 12http://tracker.habhub.org/#!qm=All&q=PI_SKY_PLUS
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[19:21] <jededu> ping upu
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[19:35] <Lunar_Lander> hello
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[19:44] <Upu> hi jededu
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[19:51] <SpacenearUS> New vehicle on the map: 03LORA1 - 12http://tracker.habhub.org/#!qm=All&q=LORA1
[19:53] <jededu> Hi upu did you manage to send inductors ?
[19:53] <Upu> hmm
[19:53] <Upu> Sent them the other day
[19:54] <Upu> should have had them today
[19:54] <jededu> Ok ths to school ?
[19:54] <Upu> yes
[19:54] <jededu> Ah half term they will be held at PO
[19:54] <Upu> ah ok
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[20:13] <Zeusking19> Hey all
[20:13] <Upu> evening Zeusking19
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[20:22] <SpacenearUS> New vehicle on the map: 03ea5177ure_chase - 12http://tracker.habhub.org/#!qm=All&q=ea5177ure_chase
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[20:26] <Zeusking19> A wild chase car appeared
[20:26] <Zeusking19> :
[20:26] <Zeusking19> :P
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[20:29] <infaddict> hey guys is it normal for a GPS to take 3.5 to 4 mins to acquire any sats? located at ground level in open space. Works fine after that just wondered if that time is expected.
[20:30] <adamgreig> for a cold start, for a reasonably poor signal, sure
[20:30] <pc1pcl> cold start? http://en.wikipedia.org/wiki/Time_to_first_fix
[20:31] <infaddict> yep cold start. after 230 secs acquired 6 sats and valid lock. then upwards to 8 and 9 sats 20 secs later.
[20:32] <pc1pcl> so actually quite quick then ;)
[20:32] <infaddict> cool so sounds normal. i plan to add some status lED's to my board to alert me when I have 4+ sats and valid fix.
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[20:32] <infaddict> thx
[20:33] <infaddict> now to figure out the bitshifts to get some flags i need
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[20:36] <infaddict> oh i had a question on altitude. mean sea level or ellipsoid. i think i understand the difference, just wondering which one people tend to log.
[20:36] <infaddict> about 50 mtrs difference in my location
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[20:53] <Zeusking19> I have some good news regarding my balloon project - I have secured a donation from someone I know to go towards equipment for the payload, which makes it easier for me to cover the costs. I guess this pretty much confirms that I will be flying a HAB at some point :)
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[20:56] <Geoff-G8DHE> Sounds good Zeusking19, don't forget to ask suppliers if they can do a discount as well ;-)
[20:56] <Zeusking19> :)
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[20:56] <SpacenearUS> New vehicle on the map: 03VEGA-I - 12http://tracker.habhub.org/#!qm=All&q=VEGA-I
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[21:08] <Vaizki> Zeusking19: congrats on the free money!
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[21:10] <lz1dev> !hysplit add VENUS1-3
[21:10] <SpacenearUS> 03lz1dev: Added 03VENUS1-3 to defaults
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[21:23] <Upu> hey Babs_ https://www.youtube.com/watch?v=qVj82qPfAQ8&ab_channel=AnthonyStirk
[21:23] <Babs_> Yowza Upu - when designing my board, any particular reason why i shouldn't program through FTDI rather than ICSP (I am already using the mosi,miso and sck pins connected to the SD card)?
[21:24] <zyp> Babs_, what about the fact that chips don't come from the factory with a serial bootloader?
[21:24] <Upu> that
[21:24] <Upu> and you don't need to
[21:25] <Upu> programmer is a better bet
[21:25] <Upu> you'll need one anyway to set the fuses
[21:26] <Babs_> i presume then that i need a slight redesign of the schematic then Anthony, with some of those cryptic pull up resistors somewhere along the line?
[21:26] <Babs_> nice hard drives
[21:26] <Babs_> are they both rotating the same way, or contra rotating?
[21:26] <Upu> thats just on a frame ramping from min to max speed
[21:26] <Upu> contra
[21:26] <Upu> going to play tommorrow running them at a constant speed then reducing one slightly
[21:27] <Babs_> as in if i look at it end on one is coming towards me and one away from me?
[21:27] <Upu> note the 3D printed frame :)
[21:27] <Babs_> or both going away/both coming towards me?
[21:27] <Upu> Can't remember
[21:28] <Babs_> so if they are going in opposite directions when looking at it end on, you will generate torque around the vertical axis
[21:28] <Upu> thats the plan
[21:28] <Babs_> but you will only have one way torque I think?
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[21:29] <Upu> tbh not thought that far ahead
[21:29] <Upu> in my head if I reduce one and speed the other up and vice versa I should be able to go both ways
[21:29] <Vaizki> mmm.. Wiha screwdrivers.. use them myself as well.
[21:29] <Upu> it resisted turning with some force
[21:29] <Babs_> nope, you will just get more or less torque but both in the same direction
[21:30] <Vaizki> it will not generate torque around the axis it's hanging on
[21:30] <Upu> should be able to reverse the motor
[21:31] <Babs_> thats the issue, you can't stop and reverse it quickly enough to achieve the level of control you are looking for
[21:31] <Upu> ah
[21:31] <Babs_> (this was my world of pain in mid 2014)
[21:31] <Upu> ok
[21:31] <Geoff-G8DHE> Wow and storage for all the flight data as well ;-)
[21:31] <Upu> lol
[21:31] <Babs_> arf
[21:31] <Upu> ok well
[21:31] <Upu> Plan B
[21:31] <Upu> mount in a cage
[21:31] <Babs_> its not all lost, you can still get it to work - let me draw a sketch
[21:31] <kc2pit> Oh gods. Are you using hard drives as reaction wheels? Or just gyros?
[21:31] <Babs_> 2 secs
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[21:31] <Upu> and use a servo to tilt it
[21:32] <Babs_> well, more like 120
[21:32] <kc2pit> CMGs!
[21:32] <Babs_> no sketch necessary
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[21:32] <Babs_> in your vid, imagine they are rotating around a rod inserted vertically into your laptop screen
[21:33] <Babs_> then if they are both rotating in the same direction you can do it
[21:33] <Upu> http://youtu.be/UZlW1a63KZs?t=50s
[21:33] <Vaizki> I am vividly imagining them inserted into upu's laptop screen with bits of upufingers included :O
[21:33] <Babs_> because tilted one way they will be rotating clockwise, and the other way counterclockwise
[21:33] <Upu> yeah so heck even just one platter
[21:34] <Upu> in a cage that rotates should do ti
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[21:34] <Babs_> the only torque you would get would be a slight angle to the vertical
[21:34] <Babs_> put two in because then you can balance it in the middle of your package
[21:34] <kc2pit> Look up "control moment(um) gyroscope" if you haven't already.
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[21:35] <Babs_> the best thing about the hard drive wheels is that you dont need to balance them as i had to with my reaction wheels
[21:35] <Upu> Looking kc2pit
[21:35] <kc2pit> If you've grown bored with reaction wheels, or tired of their inefficiency, and find their control algorithms insufficiently complicated, they're how you point spacecraft.
[21:36] <kc2pit> And you've just invented them.
[21:36] <Vaizki> o'rly..
[21:37] <Upu> I feel this may not be ready for March
[21:38] <Vaizki> the idea is to stabilize the payload after burst?
[21:38] Action: daveake codes up his camera/servo/compass
[21:38] <Upu> no
[21:38] <daveake> march is the clue
[21:38] <Upu> to point a payload at the sun
[21:38] <Vaizki> ah
[21:38] <Babs_> have you got it linked to the gyro yet upu?
[21:38] <Upu> thought the flight to capture the eclipise
[21:38] <kc2pit> One-axis control may not be so bad. Three-axis may require extra cerebral cooling.
[21:39] <Upu> No Babs_ we just did the frame today
[21:39] <Upu> all it does is spin the motors up
[21:39] <daveake> so long as the sun is within the camera's view, job jobbed
[21:39] <Vaizki> I guess at the decisive moment it won't be
[21:39] <daveake> it's not a moment
[21:40] <Babs_> there is a further problem you have probably considered but may not have
[21:40] <Upu> unlikely
[21:40] <Babs_> just because it is an eclipse on the ground it doesn't mean it is an eclipse at 30km high
[21:40] <Vaizki> I thought the eclipsed area is larger the higher you go?
[21:40] <daveake> 89% on the ground
[21:41] <daveake> 90% at 30km
[21:41] <Babs_> wasn't what i meant
[21:41] <Babs_> thats ok if the eclipse is directly overhead
[21:41] <kc2pit> Right, you've got to account for the angle of the shadow.
[21:41] <daveake> the full 100% shadow is above us
[21:41] <Babs_> if it isn't then you need to find where the sun is, draw a line in 3D space and launch so it passes through that line
[21:41] <daveake> so the balloon will be closer to it
[21:41] <kc2pit> Get the balloon sunward of the eclipse ground track.
[21:41] <Vaizki> well the moon is a bit further away than 30km so yes theoretically you can be left in the light but it's not a big margin
[21:42] <daveake> we aren't close enough to get the full eclipse
[21:44] <LazyLeopard> If it's a sunny day it'll seem a little less bright. If it's a cloudy day it'll feel a lot more gloomy. ;)
[21:44] <Babs_> this is sort of what i am on about. directly above the ground eclipse, balloon has full view of the sun https://www.flickr.com/photos/91049302@N00/16582896591/
[21:44] <Babs_> it might be that you can't get high enough even a 30km for it to be a problem
[21:45] <Babs_> don't know but some calcs should tell you
[21:45] <daveake> OK you have that wrong, for the UK
[21:45] <daveake> move the UK over to underneath the shadow on the right of your drawing
[21:46] <Babs_> ahh ok, so it is (say) in France, you are launching from the Uk and intercepting it?
[21:46] <kc2pit> Last I checked, the UK was largely outside the tropics.
[21:46] <daveake> The eclipse hits the Faroe Islands
[21:46] <daveake> North of the UK
[21:46] <kc2pit> So there's a nonzero angle away from vertical.
[21:46] <daveake> The sun will be in the south east
[21:47] <Babs_> ahhh i thought it was an eclipse in the UK
[21:47] <daveake> So the column of shadow from the moon goes above the UK hitting the ground several hundred miles north
[21:47] <kc2pit> Ahh.
[21:47] <daveake> nope
[21:47] <Babs_> understood
[21:47] <daveake> 90%
[21:47] <daveake> I think I mentioned that :p
[21:47] <daveake> We get any extra 1% from the balloon (not that that's the point - we'd get more by driving to the north of scotland)
[21:47] <Babs_> "the full 100% shadow is above us" i took as meaning above us in altitude
[21:47] <daveake> which (if plan A doesn't happen) is exactly what we're doing
[21:48] <Babs_> not in latitude
[21:48] <daveake> well it is above us in altitude
[21:48] <Babs_> depends on your frame of reference
[21:48] <Babs_> :-)
[21:48] <daveake> :)
[21:48] <daveake> The balloon will be closer to it than we are
[21:49] <Babs_> i think there is probably someway of using the fact that the ublox outputs in a sun centred frame of reference too to help you
[21:49] <Babs_> rather than the earth centred one which we commonly use
[21:50] <Vaizki> being the center of the universe is very handy, I get to skip a lot of math
[21:51] <pc1pcl> instead of aiming the camera at the sun, perhaps just make sure it spins so will be pointed at the sun some of the time?
[21:51] <Vaizki> with loads of rolling shutter skew included
[21:52] <Vaizki> (I am boldly assuming video)
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[22:40] <SpacenearUS> New vehicle on the map: 03K6RPT-11 - 12http://tracker.habhub.org/#!qm=All&q=K6RPT-11
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[23:24] <NormanOK> Hello everyone, do any of you know what kind of balloon Venus1-3 uses?
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[23:42] <NormanOK> It's been floating at 18-19 km for a while now. I'm guessing it is bigger than a 36inch foil balloon.
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[23:50] <Laurenceb_> whats a while?
[23:51] <Laurenceb_> oh i see
[23:51] <Laurenceb_> California
[23:53] <NormanOK> yeah, it's been afloat for 5+ days I think.
[23:56] <lz1dev> if google has nothing chances are nobodoy knows :)
[23:57] <NormanOK> if my calculations are right, Venus1-3's payload's weight must be ~7% of its maximum lift. for a ~15 gr payload that's ~215 gr lift.
[23:58] <Laurenceb_> itd be nice to see some other custom envelope construction methods
[23:58] <Laurenceb_> other than Leos :D
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[00:00] --- Fri Feb 20 2015