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-rw-r--r--src/arch/arduino-nano/driver/i2c.cc146
1 files changed, 146 insertions, 0 deletions
diff --git a/src/arch/arduino-nano/driver/i2c.cc b/src/arch/arduino-nano/driver/i2c.cc
new file mode 100644
index 0000000..a644ca9
--- /dev/null
+++ b/src/arch/arduino-nano/driver/i2c.cc
@@ -0,0 +1,146 @@
+#include "driver/i2c.h"
+#include <avr/io.h>
+
+/*
+ * Send an I2C (re)start condition and the EEPROM address in read mode. Returns
+ * after it has been transmitted successfully.
+ */
+static signed char i2c_start_read(unsigned char addr)
+{
+ TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN);
+ while (!(TWCR & _BV(TWINT)));
+ if (!(TWSR & 0x18)) // 0x08 == START ok, 0x10 == RESTART ok
+ return -1;
+
+ // Note: The R byte ("... | 1") causes the TWI momodule to switch to
+ // Master Receive mode
+ TWDR = (addr << 1) | 1;
+ TWCR = _BV(TWINT) | _BV(TWEN);
+ while (!(TWCR & _BV(TWINT)));
+ if (TWSR != 0x40) // 0x40 == SLA+R transmitted, ACK receveid
+ return -2;
+
+ return 0;
+}
+
+/*
+ * Send an I2C (re)start condition and the EEPROM address in write mode.
+ * Returns after it has been transmitted successfully.
+ */
+static signed char i2c_start_write(unsigned char addr)
+{
+ TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN);
+ while (!(TWCR & _BV(TWINT)));
+ if (!(TWSR & 0x18)) // 0x08 == START ok, 0x10 == RESTART ok
+ return -1;
+
+ TWDR = (addr<< 1) | 0;
+ TWCR = _BV(TWINT) | _BV(TWEN);
+ while (!(TWCR & _BV(TWINT)));
+ if (TWSR != 0x18) // 0x18 == SLA+W transmitted, ACK received
+ return -2;
+
+ return 0;
+}
+
+/*
+ * Send an I2C stop condition.
+ */
+static signed char i2c_stop()
+{
+ TWCR = _BV(TWINT) | _BV(TWSTO) | _BV(TWEN);
+}
+
+/*
+ * Sends len bytes to the EEPROM. Note that this method does NOT
+ * send I2C start or stop conditions.
+ */
+static signed char i2c_send(uint8_t len, uint8_t *data)
+{
+ uint8_t pos = 0;
+
+ for (pos = 0; pos < len; pos++) {
+ TWDR = data[pos];
+ TWCR = _BV(TWINT) | _BV(TWEN);
+ while (!(TWCR & _BV(TWINT)));
+ if (TWSR != 0x28) // 0x28 == byte transmitted, ACK received
+ return pos;
+ }
+
+ return pos;
+}
+
+/*
+ * Receives len bytes from the EEPROM into data. Note that this method does
+ * NOT send I2C start or stop conditions.
+ */
+static signed char i2c_receive(uint8_t len, uint8_t *data)
+{
+ uint8_t pos = 0;
+
+ for (pos = 0; pos < len; pos++) {
+ if (pos == len-1) {
+ // Don't ACK the last byte
+ TWCR = _BV(TWINT) | _BV(TWEN);
+ } else {
+ // Automatically send ACK
+ TWCR = _BV(TWINT) | _BV(TWEN) | _BV(TWEA);
+ }
+ while (!(TWCR & _BV(TWINT)));
+ data[pos] = TWDR;
+ /*
+ * No error handling here -- We send the acks, the EEPROM only
+ * supplies raw data, so there's no way of knowing whether it's still
+ * talking to us or we're just reading garbage.
+ */
+ }
+
+ return pos;
+}
+
+signed char I2C::setup()
+{
+ TWSR = 0;
+ TWBR = ((F_CPU / 100000UL) - 16) / 2;
+
+ return 0;
+}
+
+void I2C::scan(unsigned int *results)
+{
+ for (unsigned char address = 0; address < 128; address++) {
+ if (i2c_start_read(address) == 0) {
+ results[address / (8 * sizeof(unsigned int))] |= 1 << (address % (8 * sizeof(unsigned int)));
+ }
+ }
+ i2c_stop();
+}
+
+signed char I2C::xmit(unsigned char address,
+ unsigned char tx_len, unsigned char *tx_buf,
+ unsigned char rx_len, unsigned char *rx_buf)
+{
+ unsigned char i;
+
+ if (tx_len) {
+ if (i2c_start_write(address) < 0) {
+ return -1;
+ }
+ if (i2c_send(tx_len, tx_buf) < 0) {
+ return -1;
+ }
+ }
+ if (rx_len) {
+ if (i2c_start_read(address) < 0) {
+ return -1;
+ }
+ if (i2c_receive(rx_len, rx_buf) < 0) {
+ return -1;
+ }
+ }
+
+ i2c_stop();
+ return 0;
+}
+
+I2C i2c;