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SX1272 with STM32L452CEU6 weird Signals

Hello there,
I got some really weird Problems, which i can't resolve myself.
I'm using a STM32L452CEU6 with a SX1272 on a custom made board with the reference schematic provided by semtech:

https://semtech.my.salesforce.com/sfc/p/E0000000JelG/a/2R0000001NNb/CcLmIvttsaICaBS6YAyOPgwd5Hj84Kwm0ei890X76dc

The main settings are:
-PA_BOOST with 17dBm outputpower.
-implicitheader on.
-crc off.
-Frequency at 868.34 Mhz. (Europe, Germany)
-SF7.
-BW 125khz.
-one packet mode.

Trying to send just 14 Random Bytes by loading them into the FIFO, setting payloadlength register and send it via TX mode till the TXDone flag is registert (should get back to LoRa_standby by itself after the Tx is done !?)

Here starts my problem:
I read out all the registers before the TX mode is set and everything looks fine, but as soon as the TX mode starts, it sends without stopping and the signal itself is... yeah look at the pictures:

first one is pycom lopy with LoRa 14 byte package and it works fine.
second one is the SX1272 wit STM32.
lopy with a SF of 7 and 125khz BW, SX with SF8 and 125khz BW and i didn't change a setting in cubicsdr, which means the on the air time of the lopy is around 50ms and for one loop (signal looks very repetitive) the SX1272 needs around 2secs.

Tried different settings and the results got more confusing. Setting the SF to 7 and BW to 125khz results in pic 3, which doesn't even look like LoRa anymore.

I hope you guys got an idea. need it for my bachelor thesis, so i'm still a newbie to these things.

Thanks,
Christian S.


Image Attachments
lopy.pngsx1272_sf8_125khz.pngsx1272_sf7_125khz.png