This is simplest soft I2C library (with bug fix NACK state)
SoftI2C.h
/**
* @brief SoftI2C
* interface to I2C (two-wire) communication.
*/
#include "wirish.h"
#ifndef _SOFTI2C_H_
#define _SOFTI2C_H_
#define SI2C_SUCCESS 0 /* transmission was successful */
#define SI2C_ENACKADDR 2 /* received nack on transmit of address */
#define SI2C_ENACKTRNS 3 /* received nack on transmit of data */
#define SI2C_WRITE 0
#define SI2C_READ 1
static inline void SI2C_DELAY(uint8 delay)
{
for(uint8 i = 0; i < delay; i++)
asm volatile("nop");
}
class SoftI2CClass
{
private:
GPIO_Port *sda_port, *scl_port;
uint8 sda_pin, scl_pin;
// uint8 writeOneByte(uint8 address);
// uint8 readOneByte(uint8 address, uint8 *data);
void i2c_start(void);
void i2c_stop(void);
uint8 i2c_get_ack(void);
void i2c_send_ack(void);
void i2c_send_nack(void);
uint8 i2c_shift_in(void);
void i2c_shift_out(uint8 val);
public:
SoftI2CClass(void);
uint8 SDA, SCL;
uint8 Delay;
uint8 Data;
uint8 SlaveAddress;
void begin(uint8 sda, uint8 scl);
uint8 writeReg(uint8 register_address, uint8 data);
uint8 writeReg(uint8 slave_address, uint8 register_address, uint8 data);
uint8 readReg(uint8 register_address);
uint8 readReg(uint8 register_address, uint8 *data);
uint8 readReg(uint8 slave_address, uint8 register_address);
uint8 readReg(uint8 slave_address, uint8 register_address, uint8 *data);
};
extern SoftI2CClass SoftI2C;
#endif // _SoftI2C_H_
SoftI2C.cpp
/**
* @brief SoftI2C
* interface to I2C (two-wire) communication.
*/
#include "wirish.h"
#include "gpio.h"
#include "SoftI2C.h"
// Define for PORT/PIN access via gpio_read/write functions
#define SET_PIN_ACCESS() sda_port = PIN_MAP[sda].port; \
sda_pin = PIN_MAP[sda].pin; \
scl_port = PIN_MAP[scl].port; \
scl_pin = PIN_MAP[scl].pin
#define SCL_HI() gpio_write_bit(scl_port, scl_pin, 1)
#define SCL_LO() gpio_write_bit(scl_port, scl_pin, 0)
#define SDA_HI() gpio_write_bit(sda_port, sda_pin, 1)
#define SDA_LO() gpio_write_bit(sda_port, sda_pin, 0)
#define SDA_RD() gpio_read_bit(sda_port, sda_pin)
// #define SET_PIN_ACCESS()
// #define SCL_HI() digitalWrite(scl, HIGH)
// #define SCL_LO() digitalWrite(scl, LOW)
// #define SDA_HI() digitalWrite(sda, HIGH)
// #define SDA_LO() digitalWrite(sda, LOW)
// #define SDA_RD() digitalRead(sda)
#define Delay() SI2C_DELAY(Delay)
#define Delay_SCL_HI() Delay(); SCL_HI()
#define Delay_SDA_HI() Delay(); SDA_HI()
#define Delay_SCL_LO() Delay(); SCL_LO()
#define Delay_SDA_LO() Delay(); SDA_LO()
void SoftI2CClass::i2c_start(void)
{
Delay_SDA_LO();
Delay_SCL_LO();
}
void SoftI2CClass::i2c_stop(void)
{
Delay_SCL_HI();
Delay_SDA_HI();
}
uint8 SoftI2CClass::i2c_get_ack(void)
{
Delay_SCL_LO();
Delay_SDA_HI();
Delay_SCL_HI();
Delay();
if (!SDA_RD())
{
SCL_LO();
return true;
}
else
{
SCL_LO();
return false;
}
}
void SoftI2CClass::i2c_send_ack(void)
{
Delay_SDA_LO();
Delay_SCL_HI();
Delay_SCL_LO();
}
void SoftI2CClass::i2c_send_nack(void)
{
Delay_SDA_HI();
Delay_SCL_HI();
Delay();
Delay_SCL_LO();
}
uint8 SoftI2CClass::i2c_shift_in(void)
{
uint8 data = 0;
for (uint8 mask = 0x80; mask != 0; mask >>= 1)
{
Delay_SCL_HI();
Delay();
if (SDA_RD())
data |= mask;
SCL_LO();
}
return data;
}
void SoftI2CClass::i2c_shift_out(uint8 val)
{
for(uint8 mask = 0x80; mask != 0; mask >>= 1)
{
if (mask & val) { SDA_HI(); }
else { SDA_LO(); }
Delay_SCL_HI();
Delay_SCL_LO();
}
}
SoftI2CClass::SoftI2CClass(void)
{
Delay = 50;
}
/*
* Joins I2C bus as master on given SDA and SCL pins.
*/
void SoftI2CClass::begin(uint8 sda, uint8 scl)
{
SDA = sda;
SCL = scl;
SET_PIN_ACCESS();
pinMode(scl, OUTPUT_OPEN_DRAIN);
pinMode(sda, OUTPUT_OPEN_DRAIN);
SCL_HI();
SDA_HI();
uint8 retry = 250;
if (retry-- > 0 && !SDA_RD())
{
Delay_SCL_LO();
Delay_SCL_HI();
}
}
uint8 SoftI2CClass::writeReg(uint8 register_address, uint8 data)
{
return writeReg(SlaveAddress, register_address, data);
}
uint8 SoftI2CClass::writeReg(uint8 slave_address, uint8 register_address, uint8 data)
{
uint8 error = SI2C_SUCCESS;
slave_address <<= 1;
i2c_start();
i2c_shift_out(slave_address | SI2C_WRITE);
if (!i2c_get_ack())
error = SI2C_ENACKADDR;
else
{
i2c_shift_out(register_address);
if (!i2c_get_ack())
error = SI2C_ENACKTRNS;
else
{
i2c_shift_out(data);
if (!i2c_get_ack())
error = SI2C_ENACKTRNS;
}
}
Delay_SDA_LO();
i2c_stop();
return error;
}
uint8 SoftI2CClass::readReg(uint8 register_address)
{
return readReg(SlaveAddress, register_address, &Data);
}
uint8 SoftI2CClass::readReg(uint8 register_address, uint8 *data)
{
return readReg(SlaveAddress, register_address, data);
}
uint8 SoftI2CClass::readReg(uint8 slave_address, uint8 register_address)
{
return readReg(slave_address, register_address, &Data);
}
uint8 SoftI2CClass::readReg(uint8 slave_address, uint8 register_address, uint8 *data)
{
uint8 error = SI2C_SUCCESS;
slave_address <<= 1;
i2c_start();
i2c_shift_out(slave_address | SI2C_WRITE);
if (!i2c_get_ack())
{
Delay_SDA_LO();
error = SI2C_ENACKADDR;
}
else
{
i2c_shift_out(register_address);
if (!i2c_get_ack())
{
Delay();
SDA_LO();
error = SI2C_ENACKTRNS;
}
else
{
Delay();
Delay_SCL_HI();
Delay();
i2c_start();
i2c_shift_out(slave_address | SI2C_READ);
if (!i2c_get_ack())
{
Delay_SDA_LO();
error = SI2C_ENACKADDR;
}
else
{
Delay();
*data = i2c_shift_in();
i2c_send_nack();
}
}
}
i2c_stop();
return error;
}
// Declare the instance that the users of the library can use
SoftI2CClass SoftI2C;
