qmk_firmware_custom/keyboards/sx60/sx60.c

#include "sx60.h"
#include "i2cmaster.h"


bool i2c_initialized = 0;
uint8_t mcp23018_status = 0x20;

uint8_t init_mcp23018(void) {
    mcp23018_status = 0x20;

    /* I2C subsystem */

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

    /* B Pins are Row, A pins are Columns 
       Set them to output */
    mcp23018_status = i2c_start(I2C_ADDR_WRITE);    if (mcp23018_status) goto out;
    mcp23018_status = i2c_write(IODIRA);            if (mcp23018_status) goto out;
    mcp23018_status = i2c_write(0b11111111);        if (mcp23018_status) goto out;
    /* Now write to IODIRB */
    mcp23018_status = i2c_write(0b00000000);        if (mcp23018_status) goto out;
    i2c_stop();

    mcp23018_status = i2c_start(I2C_ADDR_WRITE);    if (mcp23018_status) goto out;
    mcp23018_status = i2c_write(GPPUA);             if (mcp23018_status) goto out;
    mcp23018_status = i2c_write(0b11111111);        if (mcp23018_status) goto out;
    /* Now write to GPPUB */
    mcp23018_status = i2c_write(0b00000000);        if (mcp23018_status) goto out;

out:
    i2c_stop();

    return mcp23018_status;
}