Thanks. I think my main issue is the lack of accurate frequency counter. I had hoped to get close with an SDR radio receiver as my o’scope doesn’t quite manage 435Mhz with a great deal of accuracy. The frequency I measured and calibrated to at least got me to the point that the tele-dongle flashed red when receiving packets, but obviously there was a problem with the reception/checksum so nothing valid received. I will get this cracked and I do know someone with a spectrum analyser/frequency counter that I can get hold of, just a matter of doing this.
Good to know about the bring-up script too, I think I missed that. Regards, Kieran > On 10 Aug 2018, at 19:59, Bdale Garbee <bd...@gag.com> wrote: > > Kieran Sullivan <narei...@googlemail.com> writes: > >> Oh, and when someone figures out a good way to calibrate the radio on >> the Telemega, please let me know. I’ve been trying to get it right for >> a couple of years on and off… :-) > > Oh, sorry, I thought we had the process documented but apparently in > manual section 11.8.2 we basically just tell you not to do this > yourself. We should probably add a new appendix to the manual > explaining how to do it with suitable caveats about "don't try this > unless you have the right gear and know what you're doing, or are really > desperate". > > In the meantime, if you want to cal a board, you need some way to > accurately measure frequency near 435 Mhz (Keith and I both have > high-end frequency counters locked to GPS disciplined reference > oscillators on our benches). Once you have that, there are two ways you > could go: > > First, the ao-bringup/turnon_telemega script in the ao-bringup > subdirectory of our fw/altos repo is our current production script. The > relevant bit is that it calls cal-freq with a device argument and the > SERIAL environment variable set to the board serial number to do the > frequency cal. > > The other option is to do it all by hand. Connect to the board over USB > with a terminal program, and the 'c s' command will show you the > currently configured frequency and PLL calibration factor. Use the 'C' > command to generate a steady carrier, measure the actual frequency the > board is transmitting on, and then you can calculate an updated cal > value using the equation: > > <desired frequency> / <measured frequency> * <current cal value> > > Use 'c f' to set that new cal factor, and 'c w' to write the updated > value to flash. Then use the 'C' command to confirm the board is now > transmitting on the desired frequency. > > Hope that helps! > > Bdale _______________________________________________ altusmetrum mailing list altusmetrum@lists.gag.com http://lists.gag.com/mailman/listinfo/altusmetrum
