I use S2LP at 433 MHz with proprietary narrowband protocol. Crystal 25 MHz 10 ppm XRCGB25M000F1H02R0 from Murata; capacitors 18 pF. Devices operate OK if ambient temperature is positive. When I put them into freezer they stop responding to the base ...

I am trying to use S2LP in UART OTA mode. It works well when I trasmit and receive via GPIO pins. But when I transmit via FIFO, S2LP does not add start and stop bits as it supposed to. According to S2LP datasheet rev.7 clause 7.4: "When this format...