I now tried the same with the TI board and it returned data.
Updated function for retrieving the REMS is now:
/BLS_CODE_MDID = 0x90 uint8_t wbuf[] = { BLS_CODE_MDID, 0xFF, 0xFF, 0x00 }; SPI_Transaction transaction; uint8_t dummy[] = { 0 }; uint8_t infoBuf[2]; // Configure the transaction transaction.count = sizeof(wbuf); transaction.txBuf = wbuf; transaction.rxBuf = NULL; extFlashSelect(); if (!SPI_transfer(masterSpi, &transaction)) { return 1; } // Configure the transaction transaction.count = sizeof(infoBuf); transaction.txBuf = dummy; transaction.rxBuf = infoBuf; uint8_t ret = (uint8_t) (!SPI_transfer(masterSpi, &transaction)); extFlashDeselect();