DevHeads IoT Integration ServerDIIS
DevHeads IoT Integration Server•17mo ago
Sterling

Troubleshooting Bootloader Access on Nucleo L476RG Using Nucleo L496ZG as Master

Good day guys, I need some help in troubleshooting an issue I'm having with accessing the bootloader on a Nucleo L476RG "slave" board?

I'm using a Nucleo L496ZG as the master board, with DigitalOut pins (extBoot0 and extReset) connected to the slave's BOOT0 and NRST pins. There's also a Serial instance (usart) on the master linked to the slave's UART2. It appears that BOOT1 is fixed low, so the bootloader runs instead of executing what's in SRAM.

In resetToBootloader, I set BOOT0 high, pull NRST low for 0.1 seconds, then bring it back high. This resets the slave and stops the program from running.

In initBootloader, I set up serial communication (8-bit data, even parity, 1 stop bit per AN2606) and send 0x7F to the slave, but there's no response. The logic analyzer shows the slave receives the data, but its TX line remains inactive.

What additional steps might be necessary to successfully start the bootloader? Below is the relevant portion of my code:

DigitalOut extBoot0(D7);
DigitalOut extBoot1(D6);
DigitalOut extReset(D5);

Serial usart(/* tx, rx */ D1, D0);

uint8_t rxBuffer[1];
event_callback_t serialEventCb;

void serialCb(int events) {
    printf("something happened!\n");
}

void initBootloader() {
    wait(5); // just in case?
    // Once initialized the USART1 configuration is: 8-bits, even parity, and 1 Stop bit
    serialEventCb.attach(serialCb);
    usart.format(8, SerialBase::Even, 1);
    uint8_t buffer[1024];

    // write 0x7F
    buffer[0] = 0x7F;
    usart.write(buffer, 1, 0, 0);
    printf("sending cmd\n");
    // should ack 0x79
    usart.read(rxBuffer, 1, serialEventCb, SERIAL_EVENT_RX_ALL, 0x79);
}


If it's helpful, I can provide a picture of my board setup as well.
file0.jpg
Was this page helpful?