xmodem_handle_packet.c

static xmodem_status xmodem_handle_packet(uint8_t header) {
    
    /* Contains received data and 2 bytes CRC16 */
    uint8_t received_data[X_PACKET_1024_SIZE + X_PACKET_CRC_SIZE];

    /* Contains the remaining part of the header: the packet number and the 1-complement of the packet number 
       Note: does not contains the first-byte of the header (which is passed to this function) */
    uint8_t received_header[X_PACKET_HEADER_SIZE];

    xmodem_status status = X_OK;
    uint16_t size = 0u;
    if (X_SOH == header) {
        size = X_PACKET_128_SIZE;
    } else if (X_STX == header) {
        size = X_PACKET_1024_SIZE;
    } else {
        /* Wrong header type. */
        status = X_ERROR;
    }
    uint16_t length = size + X_PACKET_CRC_SIZE;

    /* Get the packet (except for the header) from UART. */
    uart_status header_status = uart_receive(&received_header[0u], X_PACKET_HEADER_SIZE);
    uart_status packet_status = uart_receive(&received_data[0u], length);
    uart_status comm_status = UART_OK;

    /* If header or packet rx are not fine set comm_status */
    if (header_status != UART_OK || packet_status != UART_OK)
        comm_status = UART_ERROR;

    /* The last two bytes are the CRC from the host. */
    uint16_t crc_received = ((uint16_t) received_data[length - 2u] << 8u) | ((uint16_t) received_data[length - 1u]);
    /* We calculate it too. */
    uint16_t crc_calculated = xmodem_calc_crc(received_data, size);

    /* If it is the first packet, then erase the memory. */
    if (FALSE == x_first_packet_received) {

        if (FLASH_OK == flash_erase(FLASH_APP_START_ADDRESS))
        {
            x_first_packet_received = true;
        }
        else
        {
            status |= X_ERROR_FLASH;
        }

    }

    /* Error handling and flashing. */
    if (X_OK == status) {
        if (UART_OK != comm_status) {
            /* UART error. */
            status |= X_ERROR_UART;
        }
        if (xmodem_packet_number != received_header[X_PACKET_NUMBER_INDEX]) {
            /* Packet number counter mismatch. */
            status |= X_ERROR_NUMBER;
        }
        if (255u != (received_header[X_PACKET_NUMBER_INDEX] + received_header[X_PACKET_NUMBER_COMPLEMENT_INDEX])) {
            /* The sum of the packet number and packet number complement aren't 255. */
            /* The sum always has to be 255. */
            status |= X_ERROR_NUMBER;
        }
        if (crc_calculated != crc_received) {
            /* The calculated and received CRC are different. */
            status |= X_ERROR_CRC;
        }

        /* Do the actual flashing. */
        if (FLASH_OK != flash_write(xmodem_actual_flash_address, (uint32_t*) &received_data[0], (uint32_t)size/4u))
        {
            /* Flashing error. */
            status |= X_ERROR_FLASH;
        }
    }

    /* Raise the packet number and the address counters (if there wasn't any error). */
    if (X_OK == status) {
        xmodem_packet_number++;
        xmodem_actual_flash_address += size;
    }

    return status;
}