qmk_firmware/keyboards/gboards/gergoplex/gergoplex.c

/* Copyright 2021 Jane Bernhardt
  *
  * 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 "gergoplex.h"

bool i2c_initialized = 0;
i2c_status_t mcp23018_status = 0x20;

void matrix_init_kb(void) {
    matrix_init_user();
}

uint8_t init_mcp23018(void) {
    print("starting init");
    mcp23018_status = 0x20;

    // I2C subsystem

    if (i2c_initialized == 0) {
        i2c_init();  // on pins D(1,0)
        i2c_initialized = true;
        _delay_ms(1000);
    }

    // set pin direction
    // - unused  : input  : 1
    // - input   : input  : 1
    // - driving : output : 0
    uint8_t data[] = {0b11000001, 0b11111111};
    mcp23018_status = i2c_write_register(I2C_ADDR, IODIRA, data, sizeof(data), I2C_TIMEOUT);

    if (!mcp23018_status) {
        // set pull-up
        // - unused  : on  : 1
        // - input   : on  : 1
        // - driving : off : 0
        mcp23018_status = i2c_write_register(I2C_ADDR, GPPUA, data, sizeof(data), I2C_TIMEOUT);
    }

    return mcp23018_status;
}