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I am using a custom version of the DigiKeyboard library, to use a Digispark as a keyboard in the BIOS. It works on most computers, but HP 730 Thin clients dont recognize it as a keyboard.

Below is the custom version. Any suggestions on how to fix this issue? Thank you in advance for any suggestions/help.

/*
 * Based on Obdev's AVRUSB code and under the same license.
 *
 * TODO: Make a proper file header. :-)
 * Modified for Digispark by Digistump
 */
#ifndef __DigiKeyboard_h__
#define __DigiKeyboard_h__

#include <Arduino.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <avr/delay.h>
#include <string.h>

#include "usbdrv.h"
#include "scancode-ascii-table.h"

// TODO: Work around Arduino 12 issues better.
//#include <WConstants.h>
//#undef int()

typedef uint8_t byte;


#define BUFFER_SIZE 2 // Minimum of 2: 1 for modifiers + 1 for keystroke 


static uchar    idleRate;           // in 4 ms units


/* Boot protocols have been added.
 * We do allow simultaneous key presses. 
 * The report descriptor has been created with usb.org's "HID Descriptor Tool"
 * which can be downloaded from http://www.usb.org/developers/hidpage/.
 * Redundant entries (such as LOGICAL_MINIMUM and USAGE_PAGE) have been omitted
 * for the second INPUT item.
 */
const PROGMEM uchar usbHidReportDescriptor[USB_CFG_HID_REPORT_DESCRIPTOR_LENGTH] = { /* USB report descriptor */
        0x05, 0x01, // USAGE_PAGE (Generic Desktop)
        0x09, 0x06, // USAGE (Keyboard)
        0xa1, 0x01, // COLLECTION (Application)
        0x05, 0x07, // USAGE_PAGE (Keyboard)
        0x19, 0xe0, // USAGE_MINIMUM (Keyboard LeftControl)
        0x29, 0xe7, // USAGE_MAXIMUM (Keyboard Right GUI)
        0x15, 0x00, // LOGICAL_MINIMUM (0)
        0x25, 0x01, // LOGICAL_MAXIMUM (1)
        0x75, 0x01, // REPORT_SIZE (1)
        0x95, 0x08, // REPORT_COUNT (8)
        0x81, 0x02, // INPUT (Data,Var,Abs)
        0x95, 0x01, // REPORT_COUNT (1)
        0x75, 0x08, // REPORT_SIZE (8)
        0x81, 0x03, // INPUT (Cnst,Var,Abs)
        0x95, 0x05, // REPORT_COUNT (5)
        0x75, 0x01, // REPORT_SIZE (1)
        0x05, 0x08, // USAGE_PAGE (LEDs)
        0x19, 0x01, // USAGE_MINIMUM (Num Lock)
        0x29, 0x05, // USAGE_MAXIMUM (Kana)
        0x91, 0x02, // OUTPUT (Data,Var,Abs)
        0x95, 0x01, // REPORT_COUNT (1)
        0x75, 0x03, // REPORT_SIZE (3)
        0x91, 0x03, // OUTPUT (Cnst,Var,Abs)
        0x95, 0x06, // REPORT_COUNT (6)
        0x75, 0x08, // REPORT_SIZE (8)
        0x15, 0x00, // LOGICAL_MINIMUM (0)
        0x25, 0x65, // LOGICAL_MAXIMUM (101)
        0x05, 0x07, // USAGE_PAGE (Keyboard)
        0x19, 0x00, // USAGE_MINIMUM (Reserved (no event indicated))
        0x29, 0x65, // USAGE_MAXIMUM (Keyboard Application)
        0x81, 0x00, // INPUT (Data,Ary,Abs)
        0xc0 // END_COLLECTION
};


/* Keyboard usage values, see usb.org's HID-usage-tables document, chapter
 * 10 Keyboard/Keypad Page for more codes.
 */
#define MOD_CONTROL_LEFT    (1<<0)
#define MOD_SHIFT_LEFT      (1<<1)
#define MOD_ALT_LEFT        (1<<2)
#define MOD_GUI_LEFT        (1<<3)
#define MOD_CONTROL_RIGHT   (1<<4)
#define MOD_SHIFT_RIGHT     (1<<5)
#define MOD_ALT_RIGHT       (1<<6)
#define MOD_GUI_RIGHT       (1<<7)

#define KEY_A       4
#define KEY_B       5
#define KEY_C       6
#define KEY_D       7
#define KEY_E       8
#define KEY_F       9
#define KEY_G       10
#define KEY_H       11
#define KEY_I       12
#define KEY_J       13
#define KEY_K       14
#define KEY_L       15
#define KEY_M       16
#define KEY_N       17
#define KEY_O       18
#define KEY_P       19
#define KEY_Q       20
#define KEY_R       21
#define KEY_S       22
#define KEY_T       23
#define KEY_U       24
#define KEY_V       25
#define KEY_W       26
#define KEY_X       27
#define KEY_Y       28
#define KEY_Z       29
#define KEY_1       30
#define KEY_2       31
#define KEY_3       32
#define KEY_4       33
#define KEY_5       34
#define KEY_6       35
#define KEY_7       36
#define KEY_8       37
#define KEY_9       38
#define KEY_0       39

#define KEY_ENTER   40

#define KEY_SPACE   44

#define KEY_F1      58
#define KEY_F2      59
#define KEY_F3      60
#define KEY_F4      61
#define KEY_F5      62
#define KEY_F6      63
#define KEY_F7      64
#define KEY_F8      65
#define KEY_F9      66
#define KEY_F10     67
#define KEY_F11     68
#define KEY_F12     69

#define KEY_LEFT        0x50
#define KEY_RIGHT     0x4F
#define KEY_DOWN        0x51
#define KEY_UP          0x52
#define KEY_DEL         0x4C
#define KEY_TAB       0x2B
#define KEY_BACKSP    0x2A
#define KEY_TILDE     0x35
#define KEY_MINUS     0x2D
#define KEY_EQUAL     0x2E
#define KEY_L_BRACE   0x2F
#define KEY_R_BRACE   0x30
#define KEY_BACKSLASH 0x31
#define KEY_SEMICOLON 0x33
#define KEY_QUOTE     0x34
#define KEY_COMMA     0x36
#define KEY_PERIOD    0x37
#define KEY_SLASH     0x38

#define KEY_ESC       0x29


class DigiKeyboardDevice : public Print {
 public:
  DigiKeyboardDevice () {
    cli();
    usbDeviceDisconnect();
    _delay_ms(250);
    usbDeviceConnect();


    usbInit();
      
    sei();

    // TODO: Remove the next two lines once we fix
    //       missing first keystroke bug properly.
    memset(reportBuffer, 0, sizeof(reportBuffer));      
    usbSetInterrupt(reportBuffer, sizeof(reportBuffer));
  }
    
  void update() {
    usbPoll();
  }
    
    // delay while updating until we are finished delaying
    void delay(long milli) {
        unsigned long last = millis();
      while (milli > 0) {
        unsigned long now = millis();
        milli -= now - last;
        last = now;
        update();
      }
    }
  
  //sendKeyStroke: sends a key press AND release
  void sendKeyStroke(byte keyStroke) {
    sendKeyStroke(keyStroke, 0);
  }

  //sendKeyStroke: sends a key press AND release with modifiers
  void sendKeyStroke(byte keyStroke, byte modifiers) {
    sendKeyPress(keyStroke, modifiers);
  delay(10);
    // This stops endlessly repeating keystrokes:
    sendKeyPress(0,0);
  }

  //sendKeyPress: sends a key press only - no release
  //to release the key, send again with keyPress=0
  void sendKeyPress(byte keyPress) {
    sendKeyPress(keyPress, 0);
  }

  //sendKeyPress: sends a key press only, with modifiers - no release
  //to release the key, send again with keyPress=0
  void sendKeyPress(byte keyPress, byte modifiers) {
    while (!usbInterruptIsReady()) {
      // Note: We wait until we can send keyPress
      //       so we know the previous keyPress was
      //       sent.
        usbPoll();
        _delay_ms(5);
    }
    
    memset(reportBuffer, 0, sizeof(reportBuffer));
        
    reportBuffer[0] = modifiers;
    reportBuffer[3] = keyPress;
    
    usbSetInterrupt(reportBuffer, sizeof(reportBuffer));
  }
  
  size_t write(uint8_t chr) {
    uint8_t data = pgm_read_byte_near(ascii_to_scan_code_table + (chr - 8));
    sendKeyStroke(data & 0b01111111, data >> 7 ? MOD_SHIFT_RIGHT : 0);
    return 1;
  }
    
  //private: TODO: Make friend?
  uchar    reportBuffer[8];    // buffer for HID reports [ 1 modifier byte + (len-1) key strokes]
  using Print::write;
};

DigiKeyboardDevice DigiKeyboard = DigiKeyboardDevice();

#ifdef __cplusplus
extern "C"{
#endif 
  // USB_PUBLIC uchar usbFunctionSetup
    uchar usbFunctionSetup(uchar data[8]) {
    usbRequest_t    *rq = (usbRequest_t *)((void *)data);

    usbMsgPtr = DigiKeyboard.reportBuffer; //
    if ((rq->bmRequestType & USBRQ_TYPE_MASK) == USBRQ_TYPE_CLASS) {
      /* class request type */

      if (rq->bRequest == USBRQ_HID_GET_REPORT) {
                /* wValue: ReportType (highbyte), ReportID (lowbyte) */

                /* we only have one report type, so don't look at wValue */
        // TODO: Ensure it's okay not to return anything here?    
                return 0;

      } else if (rq->bRequest == USBRQ_HID_GET_IDLE) {
                //usbMsgPtr = &idleRate;
                //return 1;
                return 0;
                
      } else if (rq->bRequest == USBRQ_HID_SET_IDLE) {
                idleRate = rq->wValue.bytes[1];
                
      }
    } else {
      /* no vendor specific requests implemented */
    }
        
    return 0;
  }
#ifdef __cplusplus
} // extern "C"
#endif


#endif // __DigiKeyboard_h__
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  • 1
    Welcome to SE/Arduino! Please take the tour to learn how this site works, and read "How to Ask". Then come back and edit your question to clarify. -- Do you have access to a USB analyzer/sniffer? If so, please tap the USB connection and watch the enumeration process and what follows. -- Did you search for information of the HP's requirements for keyboards, what did you find, and why does it not help you? -- Do you have another USB keyboard that works? If so, you might want to connect it to a Linux computer and look into the system logs for difference between that and your DigiKeyboard. Dec 13, 2023 at 18:35
  • Thank you for your response. In asking what I tried, you answered my question of what I can try. Didn't know USB analyzer/sniffers existed. And the idea of checking it against a known good keyboard in linux is great. Thank you for your help! Dec 13, 2023 at 19:56
  • Thanks for the flowers! However, these are just the next steps without guarantee of progress, but might help to finally find the solution. If you do, please come back and write an actual answer, marking it (later) as accepted. Dec 13, 2023 at 20:00
  • "a custom version of the DigiKeyboard library" is likely part of the problem based on what I see. But confirmation is in what I don't see. Where is the rest of the code?
    – timemage
    Dec 13, 2023 at 20:45

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