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/* USRP E310 Firmware Atmel AVR TWI driver
* Copyright (C) 2014 Ettus Research
* This file is part of the USRP E310 Firmware
* The USRP E310 Firmware 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.
* The USRP E310 Firmware 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 the USRP E310 Firmware. If not, see <http://www.gnu.org/licenses/>.
*/
#include "i2c_twi.h"
#include "mcu_settings.h"
#include "utils.h"
#include <stdbool.h>
#include <avr/io.h>
#include <util/twi.h>
#include <util/delay.h>
static const uint8_t I2C_TIMEOUT = 10;
static inline uint8_t I2C_READ_ADDR(const uint8_t x)
{
return (x << 1) | 0x1;
}
static inline uint8_t I2C_WRITE_ADDR(const uint8_t x)
{
return (x << 1) & 0xfe;
}
void i2c_twi_init_calc(uint32_t rate)
{
uint8_t twbr;
twbr = ((F_CPU/rate)-16)/2;
TWBR = twbr;
PRR &= ~BIT(PRTWI);
/* www.mikrocontroller.net/articles/AVR_TWI says this might help ... */
TWCR &= ~(BIT(TWSTO) | BIT(TWEN));
TWCR |= BIT(TWEN);
}
void i2c_twi_init(i2c_speed_t speed)
{
switch (speed) {
case I2C_SPEED_400K:
TWBR = 16;
break;
case I2C_SPEED_100K:
TWBR = 32;
break;
default:
TWBR = 32;
break;
}
/* reset potential prescalers */
TWSR = 0;
/* www.mikrocontroller.net/articles/AVR_TWI says this might help ... */
TWCR &= ~(BIT(TWSTO) | BIT(TWEN));
TWCR |= BIT(TWEN);
}
static void i2c_twi_wait_for_complete(void)
{
uint8_t timeout = 100;
do {
_delay_us(10);
timeout--;
} while(timeout && !(TWCR & (1<<TWINT)));
}
static void i2c_twi_start(void)
{
TWCR = BIT(TWINT) | BIT(TWEN) | BIT(TWSTA);
i2c_twi_wait_for_complete();
}
static void i2c_twi_stop(void)
{
TWCR = BIT(TWINT) | BIT(TWEN) | BIT(TWSTO);
}
static uint8_t i2c_twi_recv_byte(bool ack)
{
TWCR = BIT(TWINT) | BIT(TWEN) | (ack ? BIT(TWEA) : 0);
i2c_twi_wait_for_complete();
return TWDR;
}
static void i2c_twi_send_byte(uint8_t data)
{
TWDR = data;
TWCR = BIT(TWINT) | BIT(TWEN);
i2c_twi_wait_for_complete();
}
int8_t i2c_twi_read(uint8_t addr, uint8_t reg, uint8_t *value)
{
/* start the write transaction to select the register */
i2c_twi_start();
i2c_twi_send_byte(I2C_WRITE_ADDR(addr));
i2c_twi_send_byte(reg);
/* (re)start for the actual read transaction to read back */
i2c_twi_start();
i2c_twi_send_byte(I2C_READ_ADDR(addr));
*value = i2c_twi_recv_byte(false);
i2c_twi_stop();
return 0;
}
int8_t i2c_twi_write(uint8_t addr, uint8_t reg, uint8_t value)
{
i2c_twi_start();
i2c_twi_send_byte(I2C_WRITE_ADDR(addr));
i2c_twi_send_byte(reg);
i2c_twi_send_byte(value);
i2c_twi_stop();
return 0;
}
int8_t i2c_twi_read16(uint8_t addr, uint8_t reg, uint16_t *value)
{
uint8_t msb, lsb;
/* start the write transaction to select the register */
i2c_twi_start();
i2c_twi_send_byte(I2C_WRITE_ADDR(addr));
i2c_twi_send_byte(reg);
/* (re)start for the actual read transaction to read back MSB
* then LSB, fortunately the datashit describes the opposite w.r.t ACKs*/
i2c_twi_start();
i2c_twi_send_byte(I2C_READ_ADDR(addr));
msb = i2c_twi_recv_byte(true);
lsb = i2c_twi_recv_byte(false);
i2c_twi_stop();
*value = (msb << 8) | lsb;
return 0;
}
int8_t i2c_twi_write16(uint8_t addr, uint8_t reg, uint16_t value)
{
uint8_t msb, lsb;
msb = value >> 8;
lsb = value & 0xff;
i2c_twi_start();
i2c_twi_send_byte(I2C_WRITE_ADDR(addr));
i2c_twi_send_byte(reg);
i2c_twi_send_byte(msb);
i2c_twi_send_byte(lsb);
i2c_twi_stop();
return 0;
}
/*
static const uint8_t I2C_ARA_ADDR = 0x0c;
uint8_t i2c_twi_smbus_ara(void)
{
volatile uint8_t addr;;
i2c_twi_start();
i2c_twi_send_byte(I2C_READ_ADDR(I2C_ARA_ADDR));
addr = i2c_twi_recv_byte(false);
i2c_twi_stop();
return addr;
}
*/
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