Over the Air Update BLE, STM32F2, CRC Always 0?

Question

Posted on June 05, 2018 at 17:21I would suggest opening the file attached in notepad++.Generally speaking the code makes sense. I can get it working without the CRC, which apparently is supposed to equal 0.Note the following section:if(psFirmware->ulPage == (psFirmware->ulTotalPages - 1)){ sFirmware.ucRcvdImage = TRUE; //verify FW if(sFirmware.ucUpdateWhat == fwUPDATE_CONSOLE){ ulCRC_Calc = sFirmware.ulFirstWord; sFirmware.ulAddress = UPDATE_IMAGE_ADDRESS+4; size = ((psFirmware->ulTotalPages * 12) /4)-1; }else{ ulCRC_Calc = 0; sFirmware.ulAddress = UPDATE_RADIO_ADDRESS; size = ((psFirmware->ulTotalPages * 12) /4); }  for(i = 0x000 ; i < size ; i++){ ulMemoryRead = *(__IO uint32_t*)sFirmware.ulAddress; sFirmware.ulAddress += 4; ulCRC_Calc += ulMemoryRead; //ADD the bits to calculate the checksum } if(1){//ulCRC_Calc == 0){ //verify FW image here if(sFirmware.ucUpdateWhat == fwUPDATE_CONSOLE){ FlashStatus = FLASH_ProgramWord(UPDATE_IMAGE_ADDRESS,sFirmware.ulFirstWord); if(FlashStatus != FLASH_COMPLETE){ while(1); } firmwareUpdateProc(keyFW_RESET); }else{ sFirmware.ulTotalBytes = (psFirmware->ulTotalPages * 12); firmwareUpdateRadio(); } }else{ firmwareEraseUpdateSectors(); NVIC_SystemReset(); } }The code above is saying (if I get rid of the if(1)) that the CRC of the first word, plus all of the words written to flash for the image of the app, should be 0.I have no clue why this is the case. Is it just standard for the MCU to place a value in the application address that should work this way?Thank you for your support,Daniel

Tesla DeLorean · Accepted Answer

Posted on June 14, 2018 at 18:26 Ok, so reiterating the mechanics demonstrated here    //****************************************************************************  int main(int argc, char **argv) { uint32_t test[] = { 0x11223344, 0xB14257CC };   printf('%08X (0xB14257CC) Slow
',Crc32(0xFFFFFFFF, 0x11223344)); // 0xB14257CC printf('%08X (0xB14257CC) Fast
',Crc32Fast(0xFFFFFFFF, 0x11223344)); // 0xB14257CC printf('%08X (0x00000000) Block
', Crc32FastBlock(0xFFFFFFFF, sizeof(test)/sizeof(uint32_t), test) );  // B14257CC (0xB14257CC) Slow // B14257CC (0xB14257CC) Fast // 00000000 (0x00000000) Block   return(0); }  //**************************************************************************** ________________ Attachments : stm32tst.c.zip : https://st--c.eu10.content.force.com/sfc/dist/version/download/?oid=00Db0000000YtG6&ids=0680X000006HxUt&d=%2Fa%2F0X0000000ayq%2FcEtYjpslan59HlCDfUBXdtWfKhKra.m5tZT0d8CEbaM&asPdf=false

Tesla DeLorean · Answer

Posted on June 05, 2018 at 20:22A CRC is like a long division, you look at the remainder, so if you add the computed CRC on to the end of an image, and then recompute across the new image the values should divide through in an integer fashion leaving a remainder of zero.So make sure the image being sent is suitably 'signed', with the computed CRC at the end, and a length that includes it.Not seeing an attachment in the threaded view.

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