Control a Native Instrument Komplete Kontrol A-Series keyboard via raw USB HID commands. Can read the buttons and write to the LCD screen and LEDs.

kontrol_usb_re.cpp

#include <hidapi.h>
#include <stdio.h>

int main() {
  hid_init();
  hid_device *handle = hid_open(0x17cc, 0x1750, NULL);

  // Disable local controls
  unsigned char buf1[3] = {0xa0, 0x03, 0x04};
  hid_write(handle, buf1, 3);

  // Each byte is a column of 8 pixels (0 = black, 1 = white)
  unsigned char screen_content[] = {
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
      0xff, 0xff, 0xff, 0xff};
  for (size_t i = 0; i < 256; i++) {
    screen_content[i] = 0xff - i;
  }

  // Screen high
  unsigned char buf2[256 + 9] = {
      0xe0, 0x00, 0x00, 0x00, 0x00, 0x80, 0x00, 0x02, 0x00,
  };
  for (size_t i = 0; i < 256; i++)
    buf2[i + 9] = screen_content[i];
  hid_write(handle, buf2, sizeof(buf2));

  // Screen low
  unsigned char buf3[256 + 9] = {
      0xe0, 0x00, 0x00, 0x02, 0x00, 0x80, 0x00, 0x02, 0x00,
  };
  for (size_t i = 0; i < 256; i++)
    buf3[i + 9] = screen_content[i];
  hid_write(handle, buf3, sizeof(buf3));

  // LEDs
  unsigned char buf4[] = {0x80, 0x7c, 0x7c, 0x7c, 0x0,  0x0, 0x0, 0x0,
                          0x0,  0x0,  0x0,  0x0,  0x0,  0x0, 0x0, 0x0,
                          0x0,  0x7c, 0x7e, 0x0,  0x7c, 0x7c};
  hid_write(handle, buf4, sizeof(buf4));

  // Buttons
  while (true) {
    unsigned char buf[32];
    hid_read(handle, buf, 32);
    for (int i = 0; i < 32; i++)
      printf("%02x ", buf[i]);
    printf("\n");
  }

  hid_close(handle);
  hid_exit();
  return 0;
}