7 years, 4 months ago.

Cannot send packets over USBSerial on KL25Z

I have tried many different drivers and cannot successfully send data from the uC to the computer over USBSerial. I am trying the mbed-official USBSerial driver but have had the same results with the KL25Z fork and the ST micro fork as well as mbed OS2 an OS5. I am able to receive bytes freely from the computer to the uC but I cannot send data the other direction.

I have tried 3 different methods to send data to the computer: _putc(), writeBlock(), and printf(). For all three methods, the first byte is sent back to the computer successfully but then the device gets stuck in an endless while loop on line 863 in USBDevice.cpp. This is the 'Wait for completion' portion of the USBDevice::write() function.

I do not feel that I have enough knowledge about USB interfaces to properly debug this driver.

I have published my test program here.

#include "mbed.h"
#include "USBSerial.h"
 
//Virtual serial port over USB
USBSerial serial;
DigitalOut thisLED(LED1);
char temp[1];

void receiveSerial()
{
    while (serial.readable())
    {
        temp[0] = serial._getc();
        serial._putc(temp[0]);
        //serial.writeBlock((uint8_t *) temp,1);
        //serial.printf(temp);
    }
}
 
int main(void) {
    serial.attach(&receiveSerial);
    while(1)
    {
      thisLED = !thisLED;
      wait(1);
    }
}