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RandomNumberGen SX126x

Semtech Transceivers SX126x family
#1

Figured out some more undocumented behaviour, which might help someone:

RandomNumberGen (registers 0x819-0x81C):

  • Returns the same values on repeated reads
  • Is not updated by writing to it
  • Returns “0 0 0 0” after sleep or reset
  • Is updated to new random values when you execute the “calibration” command (opcode 0x89) with the “image calibration enabled” bit set.
#2

Hi @bluewave,

There is a reference implementation of how the RNG has to be used here.

Basically, you need to put the chip in Rx mode before being able to get a number.

#3

Thanks! I didn’t know that about RX mode and random numbers.

I have made a routine that executes the ‘calibrate’ command and then returns a new random number (while remaining in Standby RC).

#4

Great! That’s cool you made it work on your side.