void ICACHE_FLASH_ATTR
i2c_init(void)
{
//Disable interrupts
ETS_GPIO_INTR_DISABLE();
//Set pin functions
PIN_FUNC_SELECT(I2C_SDA_MUX, I2C_SDA_FUNC);
PIN_FUNC_SELECT(I2C_SCK_MUX, I2C_SCK_FUNC);
//Set SDA as open drain
GPIO_REG_WRITE(
GPIO_PIN_ADDR(GPIO_ID_PIN(I2C_SDA_PIN)),
GPIO_REG_READ(GPIO_PIN_ADDR(GPIO_ID_PIN(I2C_SDA_PIN))) |
GPIO_PIN_PAD_DRIVER_SET(GPIO_PAD_DRIVER_ENABLE)
);
GPIO_REG_WRITE(GPIO_ENABLE_ADDRESS, GPIO_REG_READ(GPIO_ENABLE_ADDRESS) | (1 << I2C_SDA_PIN));
//Set SCK as open drain
GPIO_REG_WRITE(
GPIO_PIN_ADDR(GPIO_ID_PIN(I2C_SCK_PIN)),
GPIO_REG_READ(GPIO_PIN_ADDR(GPIO_ID_PIN(I2C_SCK_PIN))) |
GPIO_PIN_PAD_DRIVER_SET(GPIO_PAD_DRIVER_ENABLE)
);
GPIO_REG_WRITE(GPIO_ENABLE_ADDRESS, GPIO_REG_READ(GPIO_ENABLE_ADDRESS) | (1 << I2C_SCK_PIN));
//Turn interrupt back on
ETS_GPIO_INTR_ENABLE();
i2c_sda(1);
i2c_sck(1);
return;
}
/**
* Receive byte from the I2C bus
* returns the byte
*/
uint8 ICACHE_FLASH_ATTR
i2c_readByte(void)
{
uint8 data = 0;
uint8 data_bit;
uint8 i;
i2c_sda(1);
for (i = 0; i < 8; i++)
{
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(1);
os_delay_us(I2C_SLEEP_TIME);
data_bit = i2c_read();
os_delay_us(I2C_SLEEP_TIME);
data_bit <<= (7 - i);
data |= data_bit;
}
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
return data;
}
/**
* I2C Stop signal
*/
void ICACHE_FLASH_ATTR
i2c_stop(void)
{
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(1);
os_delay_us(I2C_SLEEP_TIME);
i2c_sda(1);
os_delay_us(I2C_SLEEP_TIME);
}
/**
* Send I2C ACK to the bus
* uint8 state 1 or 0
* 1 for ACK
* 0 for NACK
*/
void ICACHE_FLASH_ATTR
i2c_send_ack(uint8 state)
{
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
//Set SDA
// HIGH for NACK
// LOW for ACK
i2c_sda((state?0:1));
//Pulse the SCK
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(1);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
i2c_sda(1);
os_delay_us(I2C_SLEEP_TIME);
}
/**
* Receive I2C ACK from the bus
* returns 1 or 0
* 1 for ACK
* 0 for NACK
*/
uint8 ICACHE_FLASH_ATTR
i2c_check_ack(void)
{
uint8 ack;
i2c_sda(1);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(1);
os_delay_us(I2C_SLEEP_TIME);
//Get SDA pin status
ack = i2c_read();
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
i2c_sda(0);
os_delay_us(I2C_SLEEP_TIME);
return (ack?0:1);
}
// *************************************************************************************************
// @fn as_write_register
// @brief Write a byte to the pressure sensor
// @param u8 device Device address
// u8 address Register address
// u8 data Data to write
// @return u8
// *************************************************************************************************
u8 i2c_write_register(u8 device, u8 data)
{
volatile u8 success;
i2c_sda(I2C_SEND_START); // Generate start condition
i2c_write(device | I2C_WRITE); // Send 7bit device address + r/w bit '0' -> write
success = i2c_sda(I2C_CHECK_ACK); // Check ACK from device
if (!success) {
I2C_SCL_HI;
i2c_sda(I2C_SEND_STOP);
return (0);
}
i2c_write(data); // Send 8bit data to register
success = i2c_sda(I2C_CHECK_ACK); // Check ACK from device
// Slave does not send this ACK
//if (!success) return (0);
i2c_sda(I2C_SEND_STOP); // Generate stop condition
return (1);
}
/**
* Write byte to I2C bus
* uint8 data: to byte to be writen
*/
void ICACHE_FLASH_ATTR
i2c_writeByte(uint8 data)
{
uint8 data_bit;
sint8 i;
os_delay_us(I2C_SLEEP_TIME);
for (i = 7; i >= 0; i--) {
data_bit = data >> i;
i2c_sda(data_bit);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(1);
os_delay_us(I2C_SLEEP_TIME);
i2c_sck(0);
os_delay_us(I2C_SLEEP_TIME);
}
}
// Initialise the I2C communications
static void i2c_init(void)
{
// Declare variables
GPIO_InitTypeDef init;
// SDA pin configuration
init.GPIO_Pin = PIN_COMPASS_SDA;
init.GPIO_Mode = GPIO_Mode_Out_OD;
init.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(PORT_COMPASS_SDA, &init);
// SCL pin configuration
init.GPIO_Pin = PIN_COMPASS_SCL;
init.GPIO_Mode = GPIO_Mode_Out_OD;
init.GPIO_Speed = GPIO_Speed_50MHz;
GPIO_Init(PORT_COMPASS_SCL, &init);
// Initialise the states of the SDA and SCL pins
i2c_sda(1);
i2c_scl(1);
}
// Perform one step of the I2C FSM
static void i2c_step(void)
{
switch(g_i2c_state)
{
// Idle states
case I2C_IDLE: // Idle bus with SCL and SDA high
break;
case I2C_READY: // Bus ready for activity with SCL and SDA low
break;
// Start states
case I2C_START:
i2c_init(); // Sets SDA and SCL to 1
g_i2c_state = I2C_START_2;
break;
case I2C_START_2:
i2c_sda(0); // SDA falling while SCL 1 => Start bit
g_i2c_state = I2C_START_3;
break;
case I2C_START_3:
i2c_scl(0); // Now SDA and SCL are both 0, ready for bus activity
g_i2c_state = I2C_READY;
break;
// Write states
case I2C_WRITE:
i2c_sda(g_i2c_to_write & (1 << g_i2c_bit)); // SDA reflects data bit
g_i2c_state = I2C_WRITE_2;
break;
case I2C_WRITE_2:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_WRITE_3;
break;
case I2C_WRITE_3:
i2c_scl(0); // Toggle SCL low
if(g_i2c_bit == 0)
g_i2c_state = I2C_WRITE_ACK_1;
else
{
g_i2c_bit--;
g_i2c_state = I2C_WRITE;
}
break;
case I2C_WRITE_ACK_1:
i2c_sda(1); // Release SDA to allow the slave to ACK or NACK
g_i2c_state = I2C_WRITE_ACK_2;
break;
case I2C_WRITE_ACK_2:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_WRITE_ACK_3;
break;
case I2C_WRITE_ACK_3:
if(i2c_sda_read()) // Read the acknowledgement bit
g_i2c_state = I2C_WRITE_GOT_NACK;
else
g_i2c_state = I2C_WRITE_GOT_ACK;
i2c_scl(0); // Toggle SCL low
break;
case I2C_WRITE_GOT_ACK:
break;
case I2C_WRITE_GOT_NACK:
break;
// Read states
case I2C_READ:
i2c_sda(1); // Release SDA to allow the slave to transmit data
g_i2c_state = I2C_READ_2;
break;
case I2C_READ_2:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_READ_3;
break;
case I2C_READ_3:
if(i2c_sda_read())
g_i2c_read |= (1 << g_i2c_bit);
i2c_scl(0); // Toggle SCL low
if(g_i2c_bit == 0)
g_i2c_state = I2C_READ_4;
else
{
g_i2c_bit--;
g_i2c_state = I2C_READ_2;
}
break;
case I2C_READ_4:
i2c_sda(0); // Reassert control over SDA again and pull it low for an ACK
g_i2c_state = I2C_READ_ACK_1;
break;
case I2C_READ_ACK_1:
i2c_scl(1); // Toggle SCL high
g_i2c_state = I2C_READ_ACK_2;
break;
case I2C_READ_ACK_2:
i2c_scl(0); // Toggle SCL low
g_i2c_state = I2C_READ_ENDED;
break;
case I2C_READ_ENDED:
break;
// Stop states
case I2C_STOP:
i2c_sda(0);
g_i2c_state = I2C_STOP_2;
break;
case I2C_STOP_2:
i2c_scl(1);
g_i2c_state = I2C_STOP_3;
break;
case I2C_STOP_3:
i2c_sda(1);
g_i2c_state = I2C_IDLE;
break;
// Default state
default:
break;
}
}