Keyboard use sample

[otosan-maker]

Hello

I want to show in YouTube my microprocessor micropython programs in a better way, so I want to migrate it to the UNIX version.
My devices have a custom keyboard, and I send the keystrokes to the text area directly, not the correct way. I will fix it.
But I have no clues how I can integrate the keyboard to my programs, is there any sample I can read about it?

This is a screenshot of the main screen, I need to send text to the textarea.

Thanks

PD, the real colors are blueish, but that is another thread.

[kdschlosser]

You need to write a keyboard driver that will tell LVGL what keys you are wanting to input into the UI.

[kdschlosser]

I don't understand what you are wanting to know/do.

[kdschlosser]

OHHH OK I get what you are saying now...

You need to compile it like this...

python3 make.py unix DISPLAY=sdl_display INDEV=sdl_pointer INDEV=sdl_keyboard

and the code you are using is going to look like this...

from micropython import const # NOQA
import lcd_bus # NOQA

_WIDTH = const(480)
_HEIGHT = const(320)

bus = lcd_bus.SDLBus(flags=0)

buf1 = bus.allocate_framebuffer(_WIDTH * _HEIGHT * 3, 0)

import lvgl as lv # NOQA
import sdl_display # NOQA

display = sdl_display.SDLDisplay(
    data_bus=bus,
    display_width=_WIDTH,
    display_height=_HEIGHT,
    frame_buffer1=buf1,
    color_byte_order=sdl_display.BYTE_ORDER_BGR,
    color_space=lv.COLOR_FORMAT.RGB888
)
display.init()

import sdl_pointer
import sdl_keyboard
import task_handler

mouse = sdl_pointer.SDLPointer()
keyboard = sdl_keyboard.SDLKeyboard()

th = task_handler.TaskHandler(duration=5)

scrn = lv.screen_active()
scrn.set_style_bg_color(lv.color_hex(0x0000FF), 0)

slider = lv.slider(scrn)
slider.set_size(300, 25)
slider.center()

[otosan-maker]

That's it. I tested and it is working.
$ keyboard._get_key()
(0, 67)
The second value is the ASCII code, but what is the first one?

Thanks

[kdschlosser]

you are not supposed to be calling keyboard.get_key(). It is prefixed by an "" because it is a private method and not apart of the public API.

[kdschlosser]

But to answer your question. The first one is if the key is being pressed or not. Buttons have 2 states, pressed and released. LVGL produces a single pressed event and if the key is held it doesn't keep on firing pressed events, it will instead fire a long press event of the key is being held. If the key gets released then it fires a key released event. It only responds to a key being released once when going from a pressed to a released state...

state, key = keyboard._get_key()
if state == keyboard.PRESSED:
    print('key is pressed')
else:
    print('key is released')

The "key" that is returned is not always the ordinal value of the ascii code.. so always use code like this to ensure you are dealing with an ascii key and not some other key.

function_keys = {                    
    lv.KEY.BACKSPACE: 'backspace',
    lv.KEY.ENTER: 'enter',
    lv.KEY.ESC: 'escape',
    lv.KEY.DEL: 'delete',
    lv.KEY.UP: 'arrow up',
    lv.KEY.DOWN: 'arrow down',
    lv.KEY.RIGHT: 'arrow right',
    lv.KEY.LEFT: 'arrow left',
    lv.KEY.HOME: 'home',
    lv.KEY.END: 'end',
    lv.KEY.PREV: 'previous',
    lv.KEY.NEXT: 'next'
}


state, key = keyboard._get_key()
if state == keyboard.PRESSED:
    if 32 <= key <= 126:
        print(f'key `{chr(key)}` is pressed')
    else:
        print(f'function key `{function_keys.get(key, "unknown")}` pressed'
else:
    print('key is released')

you can call that function if you want to get the key because it is not consumed when you do that. There is an LVGL timer that runs code that checks to see if there are any events from the SDL Window. If there are keyboard events the event gets pushed up into the indev driver where it stores the event data so when LVGL calls the read callback in the keyboard driver that stored data is what gets returned.

If you wanted to intercept the keyboard input into LVGL you can do it one of 2 ways. You can override the _get_key method or you can also override the _keypad_cb method. The latter is what processes the SDK event and maps the SDL keys to LVGL keys.