There's a ghost in the machine!  Look at waveforms; CS randomly goes high during HAL_TransmitReceive. uint8_t EMIT_REG_I ( uint8_t R_I ) { uint8_t Ret_D; CS_0; DC_0; // SPI.TX Ret_D = SPIx_Write ( R_I ); CS_1; return Ret_D; } uint8_...