Arduino HID keyboard does not work

Question

I'm using a ItsyBitsy 32u4, Adafruit says it can act as a USB HID keyboard. The mc is based on the 32u4 which the Keyboard docs say are supported.

I have a simple sketch that prints "A" every second and should press "A". When I upload the sketch and connect to the serial port I see the print output but I don't get any key presses.

Any ideas? I'm on linux, I suspect that the controller doesn't register as a HID device, maybe I need UDEV rules or drivers?

EDIT: the keyboard works on a different computer.

#include <Keyboard.h>
void setup() {
 Serial.begin(9600);
 Keyboard.begin();
 Serial.println("Start");
}
void loop() {
 Serial.println("a");
 Keyboard.write('a');
 delay(1000);
}

• Juraj: you shoukd read the reference and study the examples
• everett1992: @Juraj I have, what do you think I missed?
• Juraj: it seemed you missed what is in the Answer. do you have a text editor open in foreground?
• everett1992: Yeah, I have a window focused that accepts and displays keyboard input. Typing on my actual keyboard displays the keys.
• Juraj: next I would try removing Serial from the sketch

Answer 1

Keyboard.press() expects a character, but you are passing a character array. Also Keyboard.press() only presses but does not release the key. Keyboard.releaseAll() can be used to release all keys.

I would try:

Keyboard.press('A') ; //note the ' instead of "
Keyboard.releaseAll();

or preferably:

Keyboard.write('A'); //handles press and release of basic keys

• everett1992: I made an error when I created my simple repo sketch, but I have tried Keyboard.press('A') and Keyboard.write('A'). Neither work.
• everett1992: I also tried Keyboard.write('a') after reading keyboard.cpp and realizing that writing 'A' sends keypesses for a and the shift modifier.

Answer 2

There was some issue with my laptop, not controller or the sketch.

I tried the my board with another computer and it worked. I tried a commercial keyboard on my first computer it also didn't work.

Both keyboards work after a reboot.