highaltitude.log.20070410

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[14:13] <defy> hey james, what kind of cell phone do you use in your balloons?
[14:13] <defy> I want to include a cell for backup, but I'm unsure of what model nokia will take AT cmds
[14:13] <defy> hrm, spose that would be on the wiki *looks*
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[15:29] <jcoxon> hey defy
[15:29] <jcoxon> i actually don't use a AT compatible phone
[15:29] <jcoxon> i use a nokia 5110
[15:29] <jcoxon> and use gnokii to chat to it
[15:30] <jcoxon> works fine
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[18:51] <edwardmoore> gps porn http://www.sparkfun.com/commerce/product_info.php?products_id=8291
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[19:50] <jcoxon> evening all
[19:52] <borism> hello
[19:52] <jcoxon> heya borism
[19:52] <jcoxon> hows everything?
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[20:52] <jcoxon> hmmmho
[20:54] <mc-> hm
[20:56] Action: jcoxon is working on his ground control software
[20:58] <mc-> I'm working on my new PIC board
[21:15] <mc-> cya
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[21:20] <Laurenceb> Hi all
[21:20] <Laurenceb> avr-dos is working woot :)
[21:21] <Laurenceb> I now have 256 mb to play with
[21:21] <Laurenceb> or whatever size sd card I can find
[21:21] <rocketboy> hiya all
[21:22] <Laurenceb> hi rocketboy
[21:22] <rocketboy> hiya lb
[21:22] <rocketboy> hey jc - I like the ground control thinggy - almost made me buy a mac
[21:23] <Laurenceb> hmm you couldnt program avrs with a mac :/
[21:23] <jcoxon> hehe
[21:23] <jcoxon> its coming along
[21:23] <jcoxon> i've now got my decode software to log
[21:24] <jcoxon> so am working out a way to pass info to ground control
[21:24] <jcoxon> ed and i thought a while ago that perhaps we should get an old powerbook off ebay to act as a groundcontrol laptop
[21:24] <rocketboy> not being able to program avrs with a mac - bonus
[21:25] <jcoxon> Laurenceb, i'm sure you could
[21:25] <Laurenceb> whats up with avrs?
[21:25] <jcoxon> doing it unix style
[21:25] <rocketboy> they are not spelt PIC
[21:25] <jcoxon> haha
[21:25] <Laurenceb> lol
[21:26] <Laurenceb> but with avrs you have avr-dos
[21:26] <rocketboy> looks like cocomodem is better than truetty
[21:26] <Laurenceb> I seriously want to make an mp3 player now
[21:26] <rocketboy> humm - another reason
[21:26] <Laurenceb> mp3 playing balloon lol
[21:26] <jcoxon> rocketboy, needs to be test methinks
[21:26] <jcoxon> it looks nice
[21:27] <jcoxon> found hte wideband rtty useful
[21:27] <jcoxon> i've got some rtty mp3 which i use to test it
[21:27] <Laurenceb> is there a windows port of cocomodem?
[21:27] <Laurenceb> or linux/unix
[21:27] <jcoxon> its mac only
[21:28] <jcoxon> its native so would be very tough to port
[21:30] <Laurenceb> http://butterflymp3.sourceforge.net/pic.html
[21:30] <Laurenceb> someone has beaten me to it
[21:30] <rocketboy> hey lb - you know about RC servos - whenyou don't send any pulses they "release" - i.e don'#t try and hold the servo in the same position?
[21:31] <Laurenceb> yep
[21:31] <Laurenceb> but its analogue and seems to be a slow release
[21:32] <Laurenceb> if you try and force a servo out of position you can feel it pulsing
[21:32] <Laurenceb> I presume that is the reaction of the circuit to the individual pulses
[21:32] <Laurenceb> ie the motor response dies off over time
[21:33] <rocketboy> presumably they therefore stop drawing current
[21:33] <Laurenceb> ye, but the amplifier will draw a few microamps
[21:33] <rocketboy> I'm just wondering if to add a feature to my servo driver PIC
[21:33] <Laurenceb> and the pot
[21:37] <rocketboy> Its am 8 bit interface - i'll use 0 to turn off the servo and 1 to 255 as valid values - with the bonus that 128 will be exactly midway
[21:37] <Laurenceb> is this for a parawing?
[21:39] <rocketboy> well amything really - its a general purpose 8 channel RC servo driver - with serial interface
[21:40] <Laurenceb> I'm thinking of using hardware pwm for servos
[21:40] <Laurenceb> but i can only get 33ms pulse repetiton rate
[21:41] <rocketboy> Yeah - I was going to use the PIC PWM - but then realized it was only a couple of channels
[21:41] <Laurenceb> 2 channels is enough for plane purposes
[21:42] <rocketboy> So I have written it all in software - accurate 8 channel pulse generation while simultaniously receiveing the serial input
[21:42] <Laurenceb> cool
[21:42] <Laurenceb> do you use timer interrupts?
[21:43] <rocketboy> Part of the problem for me was handling all the interrupts on the PIC - so by offloading it to a seperate PIC I avoid all that - and only use up one pin on the main processor
[21:44] <Laurenceb> how do you handle the serial input into the pic?
[21:44] <rocketboy> no there are no interrupts at all - its all done with instruction timing
[21:45] <Laurenceb> sounds neat
[21:45] <rocketboy> the PIC has its own USART - the code is written so that it polls the PIC USART about onece every 60 instructions or so - that way I cant miss any characters
[21:46] <Laurenceb> I see, is this written in assemply then?
[21:46] <Laurenceb> -assembly
[21:46] <rocketboy> yep - works upto about 38Kbps reliably
[21:47] <rocketboy> I expect I could have written the same thing in C - but it wouldn't have been able to work as fast
[21:47] <Laurenceb> sounds good, I havent really ever coded in asm
[21:47] <Laurenceb> should learn, but it appears really hard
[21:47] Action: jcoxon has got ground control to read the rtty stream
[21:48] <jcoxon> or anything that cocoamodem produces
[21:48] <rocketboy> its easy on the PIC - only about 40 instructions to learn - and the instruction set is really quite symetric
[21:48] <Laurenceb> hmm, guess its easy for simple stuff, but when you get to maths ect
[21:49] <Laurenceb> avr-dos is all in assembly though
[21:50] <rocketboy> yep - I got about 80% of the way through writing a payload program in assember (about 3/4 years ago) and then gave up as the maths was just too painfull
[21:50] <Laurenceb> yes, you really need a compiler for that
[21:51] <Laurenceb> avr-dos doesnt look too complicated
[21:52] <rocketboy> mind you the payload was way too complicated - I had an uplink - which had encryption keys
[21:52] <Laurenceb> but its very long..
[21:52] <Laurenceb> lol
[21:52] <rocketboy> I failed my on basic rule - keep it simple
[21:52] <rocketboy> on = own
[21:53] <jcoxon> its awfully hard to keep it simple :-p
[21:53] <Laurenceb> i'm planning on having loads of complicated stuff on ultrahab :)
[21:53] <rocketboy> yes - must put more effort into keeping it simple
[21:53] <Laurenceb> now i've got 256mb
[21:55] <Laurenceb> i'll have it wrte kml straight onto the card
[21:55] <rocketboy> anyway thats why i like the RC servo driver - keeps the main program simple
[21:55] <jcoxon> will bbl
[21:56] <rocketboy> also it acts as a level shifter - as the RC servo PIC can run on 5V while the main PIC cab run on 3.3V
[21:57] <rocketboy> cab = can
[21:57] <Laurenceb> bbl
[22:04] <rocketboy> bbl
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[23:58] <Laurenceb> http://openeeg.sourceforge.net/doc/
[00:00] --- Wed Apr 11 2007