highaltitude.log.20080401

[00:05] Action: natrium42 steals edmoore's avrs and arms
[00:06] <edmoore> gumstix it is
[00:06] <natrium42> hehe
[00:11] <Rocketboy1> what I'm looking for is a single chip low power linux - hey ho - one day
[00:13] <edmoore> You could do it in 3 chips...
[00:14] <edmoore> well, + power supply
[00:15] <Rocketboy1> yeah - I was thinking of a cut down linux (like xinu) on a single chip would be cool
[00:15] <edmoore> yeah
[00:15] <edmoore> I wish real time linux wasn't buried behind patents and IP
[00:17] <Rocketboy1> I guess its a bit heavy weight - when I 1st coded in unix it would have fitted in one of the larger single chip micros
[00:18] <edmoore> yeah I guess
[00:18] <edmoore> I'd like something like TKNernel, but with a shell
[00:19] <Rocketboy1> I think the PDP-11 that we used was about 64K
[00:20] <Rocketboy1> (of memory)
[00:21] <edmoore> if only :)
[00:21] <Rocketboy1> and that was running about 6 users
[00:23] <edmoore> just discovered that the usb signal lines are the wrong way round on the pcbs we just got made
[00:24] <edmoore> how did we let that through? gaaaarrrgghhhh
[00:24] <akawaka> what about eCos?
[00:24] <edmoore> it's it costly?
[00:24] <edmoore> isn't it*
[00:25] <Rocketboy1> yeah I guess thats the problem with making PCBs
[00:25] <edmoore> yeah it's fairly infixable
[00:25] <edmoore> un*
[00:25] <edmoore> steve would you be emenable to the idea of making a radio + gsm module?
[00:26] <edmoore> i.e. what you have already but with a gsm on a software usart
[00:26] <akawaka> ecos is open source
[00:27] <Rocketboy1> Humm - just looking at the spec of PDP11/70 that we used to use - I think a ATMEGA644 is better - so it should be possible to put a cut-down version of unix on it
[00:27] <edmoore> that's be an awesome project :)
[00:28] <Rocketboy1> yeah - i'm tempted
[00:29] <Rocketboy1> cut the bloat ot of operating systems and squeeze unix onto a single chip - humm
[00:30] <akawaka> http://www.sics.se/contiki/
[00:30] <edmoore> akawaka: eCos looks very interesting indeed
[00:30] <akawaka> knew some guys involved with it in limerick, but never used it myself
[00:31] <edmoore> contiki is very small
[00:31] <edmoore> how nice
[00:33] <edmoore> Rocketboy1: would the cameras and cutdowns need 5V or 3.3V to activate them?
[00:36] <Rocketboy1> 3.3V should do - certainly for the camera
[00:36] <Rocketboy1> 3.3v on the custdown is doable - just more of a challenge
[00:37] <Rocketboy1> cutdowns will fire OK on a good 1.5V battery
[00:38] <Rocketboy1> so the cutdown circuit has just got to be low impedance enogh to deliver 1.5V for a few hundred ms
[00:39] <edmoore> can do 5V too
[00:39] <Rocketboy1> (whthout dragging the main processor down)
[00:39] <edmoore> well, VBatt
[00:39] <edmoore> which I guesss is 6V
[00:39] <edmoore> but this is for the i/o to trigger them, not the supply
[00:40] <Rocketboy1> Oh sure 3.3v is fine
[00:40] <edmoore> I've got a bunch of 4-pin connectors - GND, 3.3V, VBatt, and a digital io which is good for 150mA - but it can be 3.3V or VBatt on the dig i/o
[00:40] <edmoore> ok cool
[00:41] <edmoore> did you read my bit further up about a radio + telit board?
[00:42] <Rocketboy1> nope - where?
[00:42] <edmoore> I was just wondering about the feasability of telling the radio modem pic to either send a radio message or send an sms using a software uart?
[00:43] <Rocketboy1> hang the GSM off the radio chip?
[00:43] <edmoore> yeah
[00:44] <Rocketboy1> yeah cool - less main processor usart pins
[00:44] <edmoore> yeah
[00:45] <edmoore> and also we can put the comm board on the bottom and a layer of insulation/foil inbetween it and the processor board to shield it a little
[00:45] <edmoore> Also, if it's snugg and warm then the telit's LDO might keep the radio a bit warmer and help with drift
[00:45] <edmoore> scarily, the telit datasheet claims it can pull 2A wheile transmitting
[00:46] <Rocketboy1> yeah mobile phones can do that - 2W I think (on 3.3V with about 50% efficency)
[00:46] <edmoore> scary
[00:48] <edmoore> anyway, this new board I'm working on (needn't be used in atlas if there's a better option but I hope it'll meet spec) has the same footprint as this (http://www.electronicsnmore.com/images/bh321b.gif) and fits on the back, located by the two power prongs
[00:48] <edmoore> so it should be a decent amount lighter than the badger board
[00:49] <edmoore> the AA holder in question has power prongs rather than the PP3 arrangement in that photo
[00:50] <Rocketboy1> sure - I know the type
[00:51] <edmoore> I hope these 1.25mm molex conns will be robust enough for ballooning
[00:51] <edmoore> can't help thinking a drop of CA might keep me sleeping a little better at night
[00:53] <Rocketboy1> yeah (depending on the plastic)
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[00:58] <Rocketboy1> gotta go - cu
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[09:27] <Laurenceb> wow batchpcb are alive
[09:28] <Laurenceb> they have emailed me ;P
[09:28] <Laurenceb> intelligent life is found :D
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[11:32] <Laurenceb> april fool? ---> http://www.google.com/virgle/index.html
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[11:58] <Laurenceb> hey edmoore
[11:58] <edmoore> morning Laurenceb
[11:58] <Laurenceb> http://www.google.com/virgle/
[11:58] <edmoore> only just....
[11:58] <Laurenceb> ^ april fool :P
[11:59] <edmoore> I was just thinking that!!
[11:59] <Laurenceb> hehe a good one
[11:59] <edmoore> checking news.bbc.co.uk for more hilarity
[12:00] <edmoore> am going to london today
[12:00] <edmoore> i wonder if 'all tube services normal' as it says here is an april fool
[12:00] <Laurenceb> http://news.bbc.co.uk/1/hi/uk_politics/7324123.stm
[12:00] <Laurenceb> ^ maybe that?
[12:01] <edmoore> hmm
[12:01] <edmoore> not sure
[12:03] <edmoore> I love th picture of tux high-fiving the martian
[12:03] <Laurenceb> hehe its brilliant
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[12:43] <edmoore> do you reckon Huub is a mr or a mrs?
[12:43] <edmoore> mr
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[12:54] <Laurenceb> edmoore: talking to me?
[12:54] <edmoore> anyone
[12:54] <edmoore> but I plucked with a mr
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[12:54] <Laurenceb> me too
[12:54] <edmoore> it's a chap from ublox trying to help me with altitude limits
[12:54] <Laurenceb> cool
[12:54] <Laurenceb> I got in touch with batchpcb
[12:55] <Laurenceb> they cant get my drill file to work :/
[12:55] <edmoore> got a reply !?!?!!? :o
[12:58] <Laurenceb> yes
[12:59] <Laurenceb> they asked if I could resend the drill file, I think either I sent the wrong one, or they messed up somewhere, so i told them to get the address correct at the same time
[12:59] <edmoore> it's like witnessing a miracle
[12:59] <Laurenceb> one way to make them get in touch :P
[13:01] <Laurenceb> its a bit odd, maybe I used the wrong script to generate the drill file... but it worked with the drc bot ok
[13:28] <Laurenceb> lmao, all featured youtube videos rickroll you
[13:29] <Laurenceb> oh dear
[13:57] <Laurenceb> edmoore: you about?
[14:06] <edmoore> Laurenceb: am now
[14:07] <Laurenceb> hi
[14:07] <Laurenceb> I've been thinking about radioc omms
[14:08] <Laurenceb> if you used the 1PPS from a lassen iq to syncronise your tx and rx
[14:08] <Laurenceb> you would get better performance
[14:08] <Laurenceb> I think its quite easy at the tx end, which is good
[14:09] <Laurenceb> you'd be limited in range to 150km or so due to the speed of light
[14:10] <Laurenceb> so the trip time would mean you started to get out of sync
[14:11] <Laurenceb> for the rx end, I'm thinking you could just send the 1PPS through a potential divider, then into the sound card
[14:11] <Laurenceb> as one stereo channel, the reciever being on the other
[14:11] <edmoore> that's a good point, though I'd hazard that 150km might be a bit too limiting
[14:12] <edmoore> I dunno
[14:12] <Laurenceb> it would be easy to fix that in software
[14:13] <Laurenceb> I'm not sure how to get stereo working... I've got some c code runnin here with FFT and a display, but its using mono
[14:14] <Laurenceb> you'd have to use the 1PPS to correct for the clock frequency drifting, at both ends
[14:15] <Laurenceb> good news is I dont think you'd need a PLL, just some fiddling with the PWM would work at the tx end
[14:15] <edmoore> sure
[14:15] <edmoore> well it sounds pretty neat
[14:16] <Laurenceb> the rx end would be a pain, you'd have to do interpolation :/
[14:16] <Laurenceb> so you kept a constant number of samples between gps pulses
[14:17] <Laurenceb> I'd probably do it with different processes and pipes
[14:18] <Laurenceb> so like a basic app to talk to the sound card, something to interpolate, a decoder, and a frontend maybe... I've only done things like this a few times
[14:20] <Laurenceb> do you follow?
[14:20] <edmoore> I think so yeah
[14:21] <Laurenceb> hmm one point is that the two channels cant be allowed to get out of sync
[14:21] <Laurenceb> not sure if thats possible... guess it depends on the driver thats used
[14:21] <edmoore> could perhaps keep it much simpler, though it's a bit of a chicken and egg thing
[14:22] <edmoore> have a counter count the number of tx cycles between pps
[14:22] <edmoore> and then transmit that
[14:22] <edmoore> if the temp changes are gradual enough the decoder should be able to keep track
[14:22] <Laurenceb> hmm you can take care of tx problems on the uC
[14:23] <Laurenceb> most of the problems lie with the fact we're useing a pc/mac for something its not really designed for
[14:23] <edmoore> yeah
[14:23] <edmoore> need a dsp
[14:23] <Laurenceb> just a uC and usb to the laptop would solve a lot of problems
[14:23] <edmoore> a complete sdr tx and rx would be nice
[14:24] <Laurenceb> a little unit with SMA in for a gps ant, usb socket and audio in would be perfect :P
[14:25] <edmoore> could be the perfect excuse to start playing with a blackfin
[14:25] <edmoore> oh lord, too many projects
[14:25] <Laurenceb> then the laptop does some FFT and logs it
[14:25] <edmoore> i wish I had no degree to do
[14:25] <Laurenceb> no, just a PIC/AVR and an spi adc would be fine
[14:26] <Laurenceb> its basically a gps synced ADC on the end of a usb cable
[14:27] <Laurenceb> takes a bunch of samples at 20Ksps or so when each bit should be being transmitted, sends them to laptop which does an FFT and writes ascii to logfile/screen
[14:29] <Laurenceb> you might want to use something like 256 baud to make it simpler
[14:31] <Laurenceb> of course with a blackfin you could do the FFT, run linux with google earth, and have a colour lcd on the top showing the position :P
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[14:31] <edmoore> exactly :)
[14:31] <Laurenceb> actually you would need a binary of google earth
[14:32] <Laurenceb> for blackfin to do that :/
[14:32] <Laurenceb> just as there is no binary for turion64, hence I cant run it on here :S
[14:34] <Laurenceb> but a little usb powered box with the basic hardware and a couple of leds on the front would be easy to make and simple to operate
[14:35] <Laurenceb> just plug it in at launches :P
[14:37] <Laurenceb> the software on the laptop would be really simple, just FFT each batch of samples, pass through the discriminator, chuck result out as a bit and splat your bits together as ascii/some other format
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[14:39] <Laurenceb> you would want to FFT a few hundered milliseconds of data every so often and graph it so the operator could check the tuning, I'd just pipe it to gnuplot
[14:42] <Laurenceb> edmoore: what do you think to trying this on "atlas" ?
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[15:02] <edmoore> Laurenceb: I think we're sticking with tried and testing with atlas
[15:02] <edmoore> it's an effort in miniaturisation, not innovation
[15:02] <edmoore> we'll try that one one of the larger payloads
[15:02] <edmoore> it's also an excuse to egt a higher fidely method for filling balloons
[15:09] <Laurenceb> what are you thinking of?
[15:17] <edmoore> some sort of strain guage or something
[15:17] <edmoore> i mean the thing is, there's no point us fighting over grams on the payload if we can only get the nozzle lift somewhere between 150-200g
[15:18] <edmoore> so we need sommit a bit more accurate
[15:18] <Laurenceb> yes
[15:18] <Laurenceb> on Ultrahab we used milk bottles
[15:21] <edmoore> I also want to charcterise diffusion out of the envelope
[15:21] <edmoore> as that'll probably be decidedly non-trivial at this level
[15:21] <Laurenceb> that would be interesting to know
[15:22] <edmoore> maybe stick a strain guage on the balloon line and log
[15:22] <edmoore> would be a start
[15:22] <Laurenceb> erm it would have to be indoors tethered to do that :P
[15:23] <Laurenceb> I thought you meant launch it like that for a second XD
[15:25] <edmoore> nope, am serious
[15:26] <edmoore> the results would need a lot of filtering, but it's a fair assumption that it's in equilibrium so it's valid to measure tension in the balloon line
[15:26] <Laurenceb> erm if you launch it like that it will record the weight of the payload
[15:26] <Laurenceb> the drag acts on the balloon
[15:27] <edmoore> yes but you know your velocity too
[15:28] <Laurenceb> so measure air pressure and temperature
[15:28] <Laurenceb> to find viscosity
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[17:49] <Hiena> Good evening!
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[19:19] <jcoxon> hey Laurenceb, made any progress with the Lassen IQ's?
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[20:56] <Laurenceb> hi there RocketBoy
[20:59] <RocketBoy> hi laurenceb
[20:59] <RocketBoy> any sign of a launch window?
[20:59] <Laurenceb> too busy :/
[21:00] <Laurenceb> it might have to wait till summer I'm afraid
[21:00] <RocketBoy> oh - shame
[21:00] <Laurenceb> really it needs a few days spending on it to check things out...
[21:00] <Laurenceb> and I cant really spare that at the moment... and I need to revise next term
[21:01] <RocketBoy> bummer
[21:01] <Laurenceb> oh well... I do need to email my supervisor, he should theoretically be able to get it all running
[21:02] <Laurenceb> guess I'm too disorganised :/
[21:02] <Laurenceb> anyway, I was thinking about using these lassne iq modules to make a GPS syncronised radio link
[21:03] <RocketBoy> oh well as long as you get to fly it sometime
[21:03] <RocketBoy> what syncronised sampling?
[21:03] <Laurenceb> yes
[21:03] <Laurenceb> but its a pain using sound cards
[21:03] <RocketBoy> a fine idea
[21:03] <Laurenceb> so, my plan was to design a little unit that sits between the radio and pc
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[21:04] <Laurenceb> with the gps, a uC, usb to uart ic, and maybe an spi adc
[21:04] <RocketBoy> sure - well the whole thing really needs to be industrialised - somthing like DSPs on both ends
[21:05] <Laurenceb> to give you precicely timed ADC samples over the usb, which would power it
[21:05] <Laurenceb> doesnt need that much power really
[21:05] <Laurenceb> anyway, I need to cook some food, bbl
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[21:05] <RocketBoy> bbl2
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[00:00] --- Wed Apr 2 2008