Commit 8b71c58a authored by Birte Kristina Friesel's avatar Birte Kristina Friesel
Browse files

arduino-nano: i2c: Use idle waiting

parent b2f7f066

src/arch/arduino-nano/driver/i2c.cc

+21 −18
Original line number Diff line number Diff line 
#include "driver/i2c.h"

#include "arch.h"

#include <avr/io.h>

#include <avr/interrupt.h>



inline void await_twint(unsigned char twcr_values)

{

	TWCR = twcr_values | _BV(TWINT) | _BV(TWIE);

	while (!(TWCR & _BV(TWINT))) {

		arch.idle();

	}

}



/*

 * Send an I2C (re)start condition and the EEPROM address in read mode. Returns
@@ -7,16 +17,14 @@ 
 */

static signed char i2c_start_read(unsigned char addr)

{

	TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN);

	while (!(TWCR & _BV(TWINT)));

	await_twint(_BV(TWSTA) | _BV(TWEN));

	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)));

	await_twint(_BV(TWEN));

	if (TWSR != 0x40) // 0x40 == SLA+R transmitted, ACK receveid

		return -2;
@@ -29,14 +37,12 @@ static signed char i2c_start_read(unsigned char addr) 
 */

static signed char i2c_start_write(unsigned char addr)

{

	TWCR = _BV(TWINT) | _BV(TWSTA) | _BV(TWEN);

	while (!(TWCR & _BV(TWINT)));

	await_twint(_BV(TWSTA) | _BV(TWEN));

	if (!(TWSR & 0x18)) // 0x08 == START ok, 0x10 == RESTART ok

		return -1;



	TWDR = (addr<< 1) | 0;

	TWCR = _BV(TWINT) | _BV(TWEN);

	while (!(TWCR & _BV(TWINT)));

	await_twint(_BV(TWEN));

	if (TWSR != 0x18) // 0x18 == SLA+W transmitted, ACK received

		return -2;
@@ -61,8 +67,7 @@ static signed char i2c_send(uint8_t len, uint8_t *data) 


	for (pos = 0; pos < len; pos++) {

		TWDR = data[pos];

		TWCR = _BV(TWINT) | _BV(TWEN);

		while (!(TWCR & _BV(TWINT)));

		await_twint(_BV(TWEN));

		if (TWSR != 0x28) // 0x28 == byte transmitted, ACK received

			return pos;

	}
@@ -79,14 +84,7 @@ 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)));

		await_twint(_BV(TWEN) | ( _BV(TWEA) * (pos < len-1) ) );

		data[pos] = TWDR;

		/*

		 * No error handling here -- We send the acks, the EEPROM only
@@ -111,6 +109,7 @@ 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();

		}

	}

	i2c_stop();
@@ -144,3 +143,7 @@ signed char I2C::xmit(unsigned char address, 
}



I2C i2c;



ISR(TWI_vect)

{

}