How to read the volume keys from a USB keyboard

[Robmar]

I've read many posts here and on the web, even tried CoPilot, but I could not find how to get the USB controller to send data when the volume keys are pressed.

My Host keyboard driver works perfectly, but USBH_LL_GetURBState() is not returning with data for anything but "standard" key presses.

After many hours invested due to a total lack of documentation from STM, I found that the report descriptor of 146 bytes is read back by USBH_HID_GetHIDReportDescriptor() but the "consumer device" entry is not used.

But if STM had one support person publish a short guide it would save many developers many hours.

USBH_StatusTypeDef USBH_HID_KeybdInit(USBH_HandleTypeDef *phost)
{
  uint32_t x;
  HID_HandleTypeDef *HID_Handle = (HID_HandleTypeDef *) phost->pActiveClass->pData;

  keybd_info.lctrl = 0U;
  keybd_info.lshift = 0U;
  keybd_info.lalt = 0U;
  keybd_info.lgui = 0U;
  keybd_info.rctrl = 0U;
  keybd_info.rshift = 0U;
  keybd_info.ralt = 0U;
  keybd_info.rgui = 0U;

  for (x = 0U; x < sizeof(keybd_report_data); x++)
  {
    keybd_report_data[x] = 0U;
    keybd_rx_report_buf[x] = 0U;
  }

  if (HID_Handle->length > (sizeof(keybd_report_data)))
  {
    HID_Handle->length = (uint16_t)(sizeof(keybd_report_data));
  }

  HID_Handle->pData = keybd_rx_report_buf;

  if ((HID_QUEUE_SIZE * sizeof(keybd_report_data)) > sizeof(phost->device.Data))
  {
    return USBH_FAIL;
  }
  else
  {
** in the line below, I think it needs to point to the report table 65 bytes in for the "consumer devices" usage:-
    USBH_HID_FifoInit(&HID_Handle->fifo, phost->device.Data, (uint16_t)(HID_QUEUE_SIZE * sizeof(keybd_report_data)));
  }

  return USBH_OK;
}

const char USB_CLASS_SPECIFIC_DESC[] = {
     //hid report descriptor for interface 1 (keyboard)
      0x05, 0x01, //usage page (generic desktop)   //52, 53
      0x09, 0x06, //usage (keyboard)   //54, 55
      0xA1, 0x01, //collection (application) //56, 57
      0x85, 0x01,  /*   Report ID1  */
      0x05, 0x07, //usage page (key codes)   //58, 59
      0x19, 0xE0, //usage min (224) //60, 61
      0x29, 0xE7, //usage max (231) //62, 63
      0x15, 0x00, //logical min (0) //64, 65
      0x25, 0x01, //logical max (1) //66, 67
      0x75, 0x01, //report size (1) //68, 69
      0x95, 0x08, //report count (8)   //70, 71
      0x81, 0x02, //input (data, variable, absolute) [modifier byte] //72, 73
      0x95, 0x01, //report count (1)   //74, 75
      0x75, 0x08, //report size (8)    //76, 77
      0x81, 0x01, //input (constant) [reserved byte]  //78, 79
      0x95, 0x05, //report count (5)   //80, 81
      0x75, 0x01, //report size (1)    //82, 83
      0x05, 0x08, //usage page (page# for leds) //84, 85
      0x19, 0x01, //usage min (1)   //86, 87
      0x29, 0x05, //usage max (5)   //88, 89
      0x91, 0x02, //output (data, var, abs) [led report] //90, 91
      0x95, 0x01, //report count (1)   //92, 93
      0x75, 0x03, //report size (3) //94, 95
      0x91, 0x01, //output (constant) [led report padding]  //96, 97
      0x95, 0x05, //report count (5)   //98, 99
      0x75, 0x08, //report size (8) //100, 101
      0x15, 0x00, //logical min (0) //102, 103
      0x25, 0x65, //logical max (101)  //104, 105
      0x05, 0x07, //usage page (key codes)   //106, 107
      0x19, 0x00, //usage min (0)   //108, 109
      0x29, 0x65, //usage max (101) //110, 111
      0x81, 0x00, //input (data, array)   //112, 113
      0xC0,        //end collection  //114
     
   //
      0x05, 0x0C,    /*      Usage Page (Consumer Devices)      */
      0x09, 0x01,    /*      Usage (Consumer Control)         */
      0xA1, 0x01,    /*      Collection (Application)         */
      0x85, 0x02,    /*      Report ID=2                     */
      0x05, 0x0C,    /*      Usage Page (Consumer Devices)      */
      0x15, 0x00,    /*      Logical Minimum (0)               */
      0x25, 0x01,    /*      Logical Maximum (1)               */
      0x75, 0x01,    /*      Report Size (1)                  */
      0x95, 0x07,    /*      Report Count (7)               */
      0x09, 0xB5,    /*      Usage (Scan Next Track)            */
      0x09, 0xB6,    /*      Usage (Scan Previous Track)         */
      0x09, 0xB7,    /*      Usage (Stop)                  */
      0x09, 0xCD,    /*      Usage (Play / Pause)            */
      0x09, 0xE2,    /*      Usage (Mute)                  */
      0x09, 0xE9,    /*      Usage (Volume Up)               */
      0x09, 0xEA,    /*      Usage (Volume Down)               */
      0x81, 0x02,    /*      Input (Data, Variable, Absolute)   */
      0x95, 0x01,    /*      Report Count (1)               */
      0x81, 0x01,    /*      Input (Constant)               */
      0xC0,    

[Robmar]

The set idle call seems to be important to maintain dataflow, is this change going to be needed to get the volume key data to arrive?

case USBH_HID_REQ_SET_IDLE:
    // First Set_Idle for standard keyboard Report ID (0x00)
    classReqStatus = USBH_HID_SetIdle(phost, 0U, 0x00); // Send Set_Idle request
    if (classReqStatus == USBH_OK) {
        HID_Handle->ctl_state = USBH_HID_REQ_SET_IDLE_CONSUMER; // Move to next state
    } else if (classReqStatus == USBH_NOT_SUPPORTED) {
        HID_Handle->ctl_state = USBH_HID_REQ_SET_IDLE_CONSUMER; // Skip and continue
    }
    break;

case USBH_HID_REQ_SET_IDLE_CONSUMER:
    // Second Set_Idle for Consumer Control Report ID (e.g., 0x02)
    classReqStatus = USBH_HID_SetIdle(phost, 0U, 0x02);
    if (classReqStatus == USBH_OK) {
        HID_Handle->ctl_state = USBH_HID_REQ_SET_PROTOCOL; // Proceed to Set Protocol state
    } else if (classReqStatus == USBH_NOT_SUPPORTED) {
        HID_Handle->ctl_state = USBH_HID_REQ_SET_PROTOCOL; // Skip and continue
    }
    break;