Further improvements to M5Stack Cardputer keyboard integration.

 - Move the keyboard-related code from board.c to
   cardputer_keyboard.c, exposed to python as cardputer_keyboard.
 - Remove board.KEYBOARD, provide cardputer_keyboard.KEYBOARD instead.
 - Provide additional methods in cardputer_keyboard:
    - detach_serial()
    - attach_serial()
    - key_to_char(key, shift)

ports/espressif/boards/m5stack_cardputer/board.c

@@ -4,52 +4,20 @@
 //
 // SPDX-License-Identifier: MIT
 
-#include "board.h"
-#include "keymap.h"
+#include "mpconfigboard.h"
 #include "supervisor/board.h"
 #include "supervisor/shared/serial.h"
-#include "mpconfigboard.h"
 #include "shared-bindings/busio/SPI.h"
 #include "shared-bindings/fourwire/FourWire.h"
 #include "shared-bindings/microcontroller/Pin.h"
 #include "shared-module/displayio/__init__.h"
 #include "shared-module/displayio/mipi_constants.h"
-#include "shared-module/os/__init__.h"
 #include "shared-bindings/board/__init__.h"
-#include "shared-bindings/keypad/EventQueue.h"
-#include "shared-bindings/keypad/Event.h"
 #include "supervisor/shared/reload.h"
 #include "py/runtime.h"
 #include "py/ringbuf.h"
 #include "shared/runtime/interrupt_char.h"
 
-keypad_demux_demuxkeymatrix_obj_t board_keyboard;
-bool board_keyboard_serial_enabled = false;
-
-void update_keyboard(keypad_eventqueue_obj_t *queue);
-void keyboard_seq(const char *seq);
-
-const mcu_pin_obj_t *row_addr_pins[] = {
-    &pin_GPIO8,
-    &pin_GPIO9,
-    &pin_GPIO11,
-};
-
-const mcu_pin_obj_t *column_pins[] = {
-    &pin_GPIO13,
-    &pin_GPIO15,
-    &pin_GPIO3,
-    &pin_GPIO4,
-    &pin_GPIO5,
-    &pin_GPIO6,
-    &pin_GPIO7
-};
-
-keypad_event_obj_t event;
-
-char keystate[56];
-ringbuf_t keyqueue;
-char keybuf[32];
 
 #define DELAY 0x80
 
@@ -73,6 +41,7 @@ uint8_t display_init_sequence[] = {
 };
 
 
+// Overrides the weakly linked function from supervisor/shared/board.c
 void board_init(void) {
     busio_spi_obj_t *spi = common_hal_board_create_spi(0);
     fourwire_fourwire_obj_t *bus = &allocate_display_bus()->fourwire_bus;
@@ -124,124 +93,4 @@ void board_init(void) {
         );
 }
 
-void board_serial_init() {
-    board_keyboard.base.type = &keypad_demux_demuxkeymatrix_type;
-    common_hal_keypad_demux_demuxkeymatrix_construct(
-        &board_keyboard,     // self
-        3,     // num_row_addr_pins
-        row_addr_pins,     // row_addr_pins
-        7,     // num_column_pins
-        column_pins,     // column_pins
-        0.01f,     // interval
-        20,     // max_events
-        2     // debounce_threshold
-        );
-    demuxkeymatrix_never_reset(&board_keyboard);
-
-    // Wire the keyboard input to serial input (sys.stdin)
-    // unless M5STACK_CARDPUTER_KEYBOARD_SERIAL=0 in /settings.toml
-    mp_int_t enable_keyboard_serial;
-    os_getenv_err_t enable_keyboard_err = common_hal_os_getenv_int("M5STACK_CARDPUTER_KEYBOARD_SERIAL", &enable_keyboard_serial);
-    board_keyboard_serial_enabled = (enable_keyboard_err != GETENV_OK) || enable_keyboard_serial > 0;
-    if (!board_keyboard_serial_enabled) {
-        return;
-    }
-
-    ringbuf_init(&keyqueue, (uint8_t *)keybuf, sizeof(keybuf));
-    common_hal_keypad_eventqueue_set_event_handler(board_keyboard.events, update_keyboard);
-}
-
-bool board_serial_connected() {
-    return board_keyboard_serial_enabled;
-}
-
-uint32_t board_serial_bytes_available() {
-    if (board_keyboard_serial_enabled) {
-        return ringbuf_num_filled(&keyqueue);
-    } else {
-        return 0;
-    }
-}
-
-void keyboard_seq(const char *seq) {
-    while (*seq) {
-        ringbuf_put(&keyqueue, *seq++);
-    }
-}
-
-void update_keyboard(keypad_eventqueue_obj_t *queue) {
-    uint8_t ascii = 0;
-
-    if (common_hal_keypad_eventqueue_get_length(queue) == 0) {
-        return;
-    }
-
-    while (common_hal_keypad_eventqueue_get_into(queue, &event)) {
-        if (event.pressed) {
-            keystate[event.key_number] = 1;
-
-            if (keystate[KEY_CTRL]) {
-                if (keystate[KEY_ALT] && keystate[KEY_BACKSPACE]) {
-                    reload_initiate(RUN_REASON_REPL_RELOAD);
-                }
-                ascii = keymap[event.key_number];
-                if (ascii >= 'a' && ascii <= 'z') {
-                    ascii -= 'a' - 1;
-                }
-
-                if (ascii == mp_interrupt_char) {
-                    mp_sched_keyboard_interrupt();
-                }
-            } else if (keystate[KEY_SHIFT]) {
-                ascii = keymap_shifted[event.key_number];
-            } else if (keystate[KEY_FN] && event.key_number != KEY_FN) {
-                switch (event.key_number | FN_MOD) {
-                    case KEY_DOWN:
-                        keyboard_seq("\e[B");
-                        break;
-                    case KEY_UP:
-                        keyboard_seq("\e[A");
-                        break;
-                    case KEY_DELETE:
-                        keyboard_seq("\e[3~");
-                        break;
-                    case KEY_LEFT:
-                        keyboard_seq("\e[D");
-                        break;
-                    case KEY_RIGHT:
-                        keyboard_seq("\e[C");
-                        break;
-                    case KEY_ESC:
-                        ringbuf_put(&keyqueue, '\e');
-                        break;
-                }
-            } else {
-                ascii = keymap[event.key_number];
-            }
-
-            if (ascii > 0) {
-                if (keystate[KEY_ALT]) {
-                    ringbuf_put(&keyqueue, '\e');
-                } else if (keystate[KEY_OPT]) {
-                    ringbuf_put(&keyqueue, '\x10');
-                }
-                ringbuf_put(&keyqueue, ascii);
-            }
-
-        } else {
-            keystate[event.key_number] = 0;
-        }
-    }
-}
-
-char board_serial_read() {
-    if (board_keyboard_serial_enabled) {
-        return ringbuf_get(&keyqueue);
-    } else {
-        return 0;
-    }
-}
-
-// Use the MP_WEAK supervisor/shared/board.c versions of routines not defined here.
-
 // TODO: Should we turn off the display when asleep, in board_deinit() ?