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9 years, 2 months ago.

USBHID minimal cookbook example not working as expected

Hello, recently i tried the USBHID example found here: https://developer.mbed.org/cookbook/USBHID-bindings-.

I tried it with pywinusb and pyusb as the computer side program. What i can do is receive messages send from my NUCLEO-F429ZI, but the device itself does not receive any data correct. The if(hid.read(&recv_report)) in line 31 evaluates to true so something is received and the code enters the if path.

But then recv_report.length is always zero and there is no data in the report except zeros.

pyusb tells me, that it successfully sended 8 bytes. I am on Windows 10. Does anybody find a bug in my example or is this a mbed bug?

Thanks in advance, moro

slightly modified example from the cookbook

#include "mbed.h"
#include "USBHID.h"
 
//We declare a USBHID device. Input out output reports have a length of 8 bytes
USBHID hid(8, 8);
 
//This report will contain data to be sent
HID_REPORT send_report;
HID_REPORT recv_report;
 
Serial pc(USBTX, USBRX);
Timer debugTimer;

int main(void) {
    send_report.length = 8;
    debugTimer.start();

 
    while (1) {

        //Fill the report
        for (int i = 0; i < send_report.length; i++) {
            send_report.data[i] = rand() & 0xff;
        }
            
        //Send the report
        hid.send(&send_report);


        //try to read a msg
        if(hid.read(&recv_report)) {
            pc.printf("received at %d, length of report %d: ", debugTimer.read_us(), recv_report.length);
            for(int i = 0; i < 8; i++) {
                pc.printf("%d ", recv_report.data[i]);
            }
            pc.printf("\r\n");
        }
        
        wait(1.0);
    }
}
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