1 files changed, 104 insertions, 0 deletions
diff --git a/keyboards/mt40/i2c.c b/keyboards/mt40/i2c.c
new file mode 100644
index 000000000..c27f3e3d1
--- /dev/null
+++ b/keyboards/mt40/i2c.c
@@ -0,0 +1,104 @@
+/*
+Copyright 2016 Luiz Ribeiro <luizribeiro@gmail.com>
+
+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 <avr/io.h>
+#include <util/twi.h>
+
+#include "i2c.h"
+
+void i2c_set_bitrate(uint16_t bitrate_khz) {
+    uint8_t bitrate_div = ((F_CPU / 1000l) / bitrate_khz);
+    if (bitrate_div >= 16) {
+        bitrate_div = (bitrate_div - 16) / 2;
+    }
+    TWBR = bitrate_div;
+}
+
+void i2c_init(void) {
+    // set pull-up resistors on I2C bus pins
+    PORTC |= 0b11;
+
+    i2c_set_bitrate(400);
+
+    // enable TWI (two-wire interface)
+    TWCR |= (1 << TWEN);
+
+    // enable TWI interrupt and slave address ACK
+    TWCR |= (1 << TWIE);
+    TWCR |= (1 << TWEA);
+}
+
+uint8_t i2c_start(uint8_t address) {
+    // reset TWI control register
+    TWCR = 0;
+
+    // begin transmission and wait for it to end
+    TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN);
+    while (!(TWCR & (1<<TWINT)));
+
+    // check if the start condition was successfully transmitted
+    if ((TWSR & 0xF8) != TW_START) {
+        return 1;
+    }
+
+    // transmit address and wait
+    TWDR = address;
+    TWCR = (1<<TWINT) | (1<<TWEN);
+    while (!(TWCR & (1<<TWINT)));
+
+    // check if the device has acknowledged the READ / WRITE mode
+    uint8_t twst = TW_STATUS & 0xF8;
+    if ((twst != TW_MT_SLA_ACK) && (twst != TW_MR_SLA_ACK)) {
+        return 1;
+    }
+
+    return 0;
+}
+
+void i2c_stop(void) {
+    TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWSTO);
+}
+
+uint8_t i2c_write(uint8_t data) {
+    TWDR = data;
+
+    // transmit data and wait
+    TWCR = (1<<TWINT) | (1<<TWEN);
+    while (!(TWCR & (1<<TWINT)));
+
+    if ((TWSR & 0xF8) != TW_MT_DATA_ACK) {
+        return 1;
+    }
+
+    return 0;
+}
+
+uint8_t i2c_send(uint8_t address, uint8_t *data, uint16_t length) {
+    if (i2c_start(address)) {
+        return 1;
+    }
+
+    for (uint16_t i = 0; i < length; i++) {
+        if (i2c_write(data[i])) {
+            return 1;
+        }
+    }
+
+    i2c_stop();
+
+    return 0;
+}