Semtech SX1278 LORA: clkout on DIO5 not working

[elktown]

Hi,

I'm using a AI-Thinker RA-01 and RA-02 board with SX1278 ICs in Lora mode.

I can't seem to get a message with a payload longer than four to six bytes transmitted successfully with a bandwidth of 62.5kHz and a spread factor higher than 7. Usually the header (including length of packet) and the first four to six bytes of the payload are received correctly. Everything received afterwards is garbage.

My first guess was that the (very cheap, Ali-Express) AI-Thinker modules use a inaccurate crystal circuit. So I tried configuring DIO5 via REG_IOMAPPING2 as clkout to compare the two modules.

So far I haven't managed to see any signal at all on DIO5 neither during rx nor tx when the oscillator should be active. Am I missing something? Do I need to be in a specific mode to configure DIO5?

Thanks
Toby