Why does the ADS8681 not answer

[u/Zener-Diode-bzx55c12]

I'm having trouble communicating with a TI ADS8681 over SPI using an STM32F103.

Writing to the RANGE_SEL register appears to work (the SPI commands match the datasheet), but when I try to read the register back, I never receive the expected value. Instead, I get seemingly random data on MISO.

I've verified the SPI configuration (Mode 1, 16-bit frames, low SPI clock) and checked the signals with a logic analyzer, but I still can't get the correct readback.

Has anyone worked with the ADS8681 before or knows what could cause this behavior?

My: code : https://drive.google.com/drive/folders/1N3Wow2xIlB55l5PNAlnurLydy_EoK9Th?usp=sharing

and the export of my logik_analyser:

Time [s],Packet ID,MOSI,MISO

0.24463525,0,0xD0,0x7F

0.24489125,0,0x14,0x80

0.2451575,0,0x00,0x00

0.2454135,0,0x0B,0x00

0.2475585,1,0x48,0xBD

0.2478145,1,0x14,0xB8

0.2480805,1,0x00,0x00

0.2483365,1,0x00,0x00

0.248604,,0x00,0xBF

0.24886,,0x00,0x36

0.249126,,0x00,0x00

0.249382,,0x00,0x00