keychron_qmk_firmware/keyboards/al1/matrix.c

/* Copyright 2022
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "matrix.h"
#include "gpio.h"
#include "sn74x154.h"

static const pin_t row_pins[MATRIX_ROWS] = MATRIX_ROW_PINS;

/* All columns use a 74HC154 4-to-16 demultiplexer.
 * D3 is the enable pin, must be set high to use it.
 *
 *     A3   A2   A1   A0
 *     D7   D6   D5   D4
 * 0:   0    0    0    0
 * 1:   0    0    0    1
 * 2:   0    0    1    0
 * 3:   0    0    1    1
 * 4:   0    1    0    0
 * 5:   0    1    0    1
 * 6:   0    1    1    0
 * 7:   0    1    1    1
 * 8:   1    0    0    0
 * 9:   1    0    0    1
 * 10:  1    0    1    0
 * 11:  1    0    1    1
 * 12:  1    1    0    0
 * 13:  1    1    0    1
 * 14:  1    1    1    0
 * 15:  1    1    1    1
 */
static void select_col(uint8_t col) {
    sn74x154_set_addr(col);
}

static void init_pins(void) {
    for (uint8_t x = 0; x < MATRIX_ROWS; x++) {
        gpio_set_pin_input_high(row_pins[x]);
    }
}

static bool read_rows_on_col(matrix_row_t current_matrix[], uint8_t current_col) {
    bool matrix_changed = false;

    // Select col and wait for col seleciton to stabilize
    select_col(current_col);
    matrix_io_delay();

    // For each row...
    for (uint8_t row_index = 0; row_index < MATRIX_ROWS; row_index++) {
        // Store last value of row prior to reading
        matrix_row_t last_row_value = current_matrix[row_index];

        // Check row pin state
        if (gpio_read_pin(row_pins[row_index]) == 0) {
            // Pin LO, set col bit
            current_matrix[row_index] |= (MATRIX_ROW_SHIFTER << current_col);
        } else {
            // Pin HI, clear col bit
            current_matrix[row_index] &= ~(MATRIX_ROW_SHIFTER << current_col);
        }

        // Determine if the matrix changed state
        if ((last_row_value != current_matrix[row_index]) && !(matrix_changed)) {
            matrix_changed = true;
        }
    }

    return matrix_changed;
}

void matrix_init_custom(void) {
    // initialize demultiplexer
    sn74x154_init();
    sn74x154_set_enabled(true);
    // initialize key pins
    init_pins();
}

bool matrix_scan_custom(matrix_row_t current_matrix[]) {
    bool changed = false;

    // Set col, read rows
    for (uint8_t current_col = 0; current_col < MATRIX_COLS; current_col++) {
        changed |= read_rows_on_col(current_matrix, current_col);
    }

    return changed;
}