Hello,

#include "mbed.h"

Serial pc(USBTX, USBRX); // tx, rx
Serial device(p28, p27);  // tx, rx

int main() {
    while(1) {
        if(pc.readable()) {
            device.putc(pc.getc());
        }
        if(device.readable()) {
            pc.putc(device.getc());
        }
    }
}

Above is the handbook sample code. I just change the device pin to p28 and p27. On the hardware side i'm uisng MAX3232C driver. Just have a testing for p9/p13(tx) and p10/p14(rx) are working fine but p28(tx) is not working because what ever data is transmit from UART terminal is not able to receive from USB terminal.

I would like to know and confirm whether the pin is damage or is it this p28(tx) have special configure for UART feature?

Best Regards, Wen.

Sounds more like damage. My p28 works in the same fashion as the other two TX pins. Easiest way to test is don't use the MAX device. Just connect p9 to p10, p13 to p14 or p28 to p27. What you send out via USBTX loops back to USBRX like an echo.

Hello Andy,

Thanks for your reply.

I just did the easiest way testing as you mention. All the UART is working fine just the p28 to p27 not working. As my previous testing p27 is working fine. I wonder why p28 is not working since i never use this pin before...

Is it possible to fix the p28 problem? Is there any on board UART driver damage?

Best Regards, Wen.

Sounds like the pin maybe broken. Can you run the "blinky" standard program but use p28 rather than led1 and then check the pin actually goes up and down (with scope or external led etc).

If it doesn't then the pin is probably broken. support@mbed.org is then your next route I'm affraid.

Hello Andy,

Ya, "blinky" is not working as well. The multimeter showed 0 Volt and p28 doesn't short to GND. I think the pin is really broken. Ok, i try to contact support@mbed.org see what can i do..

Thanks for your advice.

Best Regards, Wen.

i also have some problem with you have you fixed it?