> Simple home-made driver for the SX1276 and SX1262 LoRa chip
Beware of what nailed the Meshtastic people: These chips don't have temperature dependent crystal oscillators. Transmitting more than a few milliseconds causing a temperature rise, throwing the clock off, causing transmission warpage, causing timing errors, causing transmission failures.
Temperature Compensated Crystal Oscillators (TCXOs) is what they should be looking for. And to be clear you can get SX1262 variants with such, eg: https://wiki.seeedstudio.com/wio_sx1262/
For the detailed run down, see https://cdn.sparkfun.com/assets/f/f/b/4/2/SX1262_AN-Recommen... page 14
> In the case of an SX1262 operating at +22 dBm in the US 902 – 928 MHz band, the frequency drift measured during the maximum LoRAWAN™ packet duration stays below the maximum limit, provided thermal insulation is implemented around the crystal during PCB design.
> At extreme temperatures (below -20 °C and above 70 °C), it is recommended to use a TCXO.
> For any other frequency bands corresponding to longer RF packet transmissions at +22 dBm, it is recommended to use a TCXO.
Theory and reality are different here.
As used in the meshtastic devices this chip does actually fail doing normal Lora transmission under reasonable conditions.
I know because I've seen the exact failure.
You've seen the failures in variants with a TCXO?
You mean they don't have temperature compensated? What you described is temperature dependent
too late to edit now :)
This is a radio module issue, not a chip issue.
Cheap modules have cheap crystals, better ones have a TCXO.
The chip itself supports using a TCXO instead of a regular crystal