Control your plane via your computer - no expensive cable needed - Page 3 - RC Groups
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Mar 13, 2010, 10:25 PM
High-power Rocket Gliders
iter's Avatar
Thank you for sharing your intuition on different latencies in your system, and your difficulty in measuring them.

Before you decide how you can measure something, you must decide what you want to measure. "Complete lag" may mean time between when you move a stick and when a servo reaches its new position. It can be the time from when you buffer your packet to when the the transmitter parses it. It can be many other things, and they all lend themselves to different measurement techniques. You may even decide to measure the feeling you get: "instant" vs. "not instant". In any case, if you can't formally describe what you are measuring, it doesn't mater how you measure it.

I reiterate my invitation to post an oscillogram of a 384kHz square wave you generate from your sound card. You already have a formal parameter to measure and already know the technique for measuring it.

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Mar 14, 2010, 11:27 PM
Registered User
you don't need to thanks me at every message :P

I cannot measure the output the way you want it. however, in my infinite friendliness (yeah, im sarcastic) i made a friend record the output from stereo 192 to stereo 192 input and opened the file as mono conversion, and at 384 instead of 192khz (192 would give wrong timing ofc)
normally i'd use a stereo to mono wire
i couldn't do that on my computer because while intel hd audio compatible cards output 192khz they have 96khz mono input for recording, and it needs either an oscope either 192khz stereo (high end audio sound cards only i suppose)

if that's what you want to see, then good for you. if you want me to buy a real oscope, well that's just not going to happen soon :P

About the lag, once again..
"complete lag" means end to end, from the moment you move the joystick to the servo moving for example. The buffer and ppm signal generation time was measured in my previous post. it excludes the time it takes for the signal to be buffered by the sound system (alsa), the travel time over the audio cable, and the radio reading the signal. it includes joystick reading for what its worth lol.

Just to be clear, i'm sorry but i lost interest into going on with this conversation. I genuinely hope the above provides the answers you are looking for, but that's as far as i'm going to go.
Mar 14, 2010, 11:33 PM
Registered User
Originally Posted by mkmkmk13
when should we expect the windows version?
after doing the capture for the other guy there wasn't much of my evening left (that's why im not going further with such replies :P) so anyway, i spent an hour (its 4h26 am :P) making the windows program work.
and it works, but it's not as smooth and nice as the linux program, so i'm not going to release it just yet. But i can fly my msr via Windows :P its just.. difficult compared to flying it from linux.. not as perfect.

For any programmer:
currently using xaudio2 with a datastream where the ppm is fed. i need a way to lock the audio output on one port as "exclusive access" (so other sounds don't interfer), and i'm also not sure xaudio2 doesn't actually resample the signal.
Going to try waveout and directsound tomorrow, worse case i'll use the asio drivers which are supposed to give alsa-like quality/latency.

on these long posts, good night guys!
Mar 15, 2010, 02:08 AM
High-power Rocket Gliders
iter's Avatar
Jim, I like to thank people who respond to my queries. Beyond simple courtesy, I like to acknowledge my partner in dialog for constructive responses.

I don't want you to buy anything and I don't want you to do anything for me. I am trying to wrap my head around what you actually have and what you have in your imagination. If, after going through the clarification exercise with me, you lose interest in making some of the claims you make originally, I support you in that. If you wish to continue making these claims, I can support you in further clarifying the claims you wish to make.

To measure a 384kHz signal, you need (again) hardware that samples at least at twice that frequency--in this case, 768kHz. This pretty much means using a real oscilloscope. I am not telling you to buy one; I am noting that without one, you cannot be sure that you actually get what you claim you get out of your sound card. The image you post shows a wave that is not square (high cycles almost twice as long as low cycles) and appears to have a period of ~0.000125 units. If these units are seconds, your wave has a frequency of 8kHz.

Mar 15, 2010, 08:04 AM
Registered User
refer to previous posts for all your claims/requests. as for the units, you might figure it out.. hint: ppm frame is 22.5ms, down signal 0.4ms, up signal 0.7 to 1.7ms (if your ppm signal had the same length up/down thats why it doesnt work)
Mar 16, 2010, 02:19 PM
High-power Rocket Gliders
iter's Avatar
Thank you for explaining what your waveform represents. I am not clear on this image illusrates with respect to the number of steps in yor PPM pulse train.

Mar 17, 2010, 10:20 PM
Registered User
The windows version now works properly :P
just been doing a few rounds with my blade msr and the joystick and its quite fine ^^
I'll try to make some usable zip of a binary tomorrow.
Mar 18, 2010, 10:43 PM
Registered User
As promised, the Windows program:

Make sure you at least read the README

you'll prolly need that:

til i make smth to reg the single dll more streamlined
it includes directx and stuff, else you'll get errors.
Last edited by jimbob00; Mar 18, 2010 at 11:32 PM.
Mar 19, 2010, 12:00 PM
mkmkmk13's Avatar
thanks jimbob
ill download it as soon as i get home
Mar 19, 2010, 05:48 PM
mkmkmk13's Avatar
so i downloaded it
after i enabled ppm the dx7 will switch very rapidly between no trainee (also beeps rapidly), so all i got was pulses on the servos and throttle (so it works) needs improvement
i am running windows 7 with HD audio sound card, i also tried to change the sampling rate on the sound card with no luck
Mar 19, 2010, 05:56 PM
Registered User
try to change the amplitude
you can record dx7's signal at proper amplitude (it depends on the sound card) also with the button of the same name
when you've the proper amplitude the dx7 lcd should not be pulsing/flashing but have a strong "dx7 spektrum"
amplitude is 16bit so it goes from 0 to 32760 approx (last few bits are reserved, before anyone tells bad stuff)
usually works between 3000 and 24000 depending on sound card, volume, etc
Jul 22, 2010, 12:40 PM
Registered User
"... most of the USB devices you'll find."

What USB devices are available that would you recommend to someone if they just didn't feel competent enough to pursue your method?
Jul 22, 2010, 12:46 PM
Registered User
see Flytron site
Jul 27, 2010, 02:37 PM
Registered User
Is there a Visual Basic project source code file for this PPM generation program?
Oct 09, 2012, 03:52 PM

sorry for bumping this old thread, but

I just want to say jimbob00 loop{ thank you } for publishing the source code.

I was scratching my head for quite a while how to make precise sound signal in C#, for making PC->RC interface.
Your solutions sort of works in my case for DX8, there is just some jitter and latency but few code tweaking should probably fix this.

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