Hi Pham Minh Thuan,
I2C example (the one that i referred to in last post) is also available for IAR workbench.
I can give some basic guidance on writing your I2C library, first of all, you need to think which method you will use: Polling or Interrupt.
In I2C example, polling is used.
There should be a function that initializes I2C module (clocking I2C module, configure I2C used pins, enable I2C module, set Slave Address and set SDA and SCL hold time):
void hal_i2c_init(void)
{
/* Clocking I2C0 module */
SIM_SCGC4 |= SIM_SCGC4_I2C0_MASK;
/* Use PTD8 as I2C0 SCL pin */
PORTD_PCR8 = PORT_PCR_MUX(2);
/* Use PTD9 as I2C0 SDA pin */
PORTD_PCR9 = PORT_PCR_MUX(2);
/* Configure I2C rate to Bus clock / (mul x SCL divider)
* for this case, Bus clock is configured to 50MHz (Core clock 100MHz, Bus clock 50MHz, see, sysinit.c)
* I2C Baud rate = 50 MHz / (2 x 160) = 156 250 kbps */
I2C0_F = 0x60;
/* Enables IICEN flag (I2C Enable) */
I2C0_C1 = 0x80;
/* As we will use MCU as master, I2C0_F isn't set
* I2C0_A1 = desired_addres_value;
* */
}
In this function, you can use some parameters for configuring your I2C module as user defined them: for example, I2C baud rate, Slave address, etc. You can also use a structure that groups these fields:
typedef struct {
uint32_t i2c_baud_rate;
uint8_t i2c_address;
bool i2c_enable_interrupt;
}I2C_CONFIG;
After configuration is achieved, you must send or request bytes to slave (configuration was made for I2C being master). You can define basic functions such as write byte, get ack, and so on (according to I2C protocol specifications). I commented function to read data from MMA8451 accelerometer in example code:
uint8_t hal_dev_mma8451_read_reg(uint8_t addr)
{
uint8_t result;
/* Configure I2C module as Master and Configure as Transmit mode */
i2c_start(I2C0_B);
/* Write to Slave address and send WRITE identifier (last bit to 0)*/
i2c_write_byte(I2C0_B, I2C_ADDR_MMA8451 | I2C_WRITE);
/* Wait for IICIF flag (One byte transfer) */
i2c_wait(I2C0_B);
/* Verify if ACK was received */
i2c_get_ack(I2C0_B);
/* As we want to send a byte (register), we send this byte*/
i2c_write_byte(I2C0_B, addr);
/* Wait for IICIF flag (One byte transfer) */
i2c_wait(I2C0_B);
/* Verify if ACK was received */
i2c_get_ack(I2C0_B);
/* Start a new transaction */
i2c_repeated_start(I2C0_B);
/* Want to read a register */
i2c_write_byte(I2C0_B, I2C_ADDR_MMA8451 | I2C_READ);
/* Wait for IICIF flag (One byte transfer) */
i2c_wait(I2C0_B);
/* Verify if ACK was received */
i2c_get_ack(I2C0_B);
/* Change to RX mode to received requested data */
i2c_set_rx_mode(I2C0_B);
/* Send a nack after receiving next byte */
i2c_give_nack(I2C0_B);
/* Read data */
result = i2c_read_byte(I2C0_B);
/* Wait until nack is sent*/
i2c_wait(I2C0_B);
/* Stop transmission (switch to slave mode and RX mode) */
i2c_stop(I2C0_B);
/* As nack was sent in last received byte, there is still one byte to be received */
result = i2c_read_byte(I2C0_B);
pause();
return result;
}
As you could see, basically, this procedure uses functions to write, get_ack and switch to slave when needed.
There is another way to implement this driver, it could be made using interrupt, this is done by setting IICIE bit in I2C_C1 register, as all I2C interrupt sources uses the same interrupt vector, you need to implement routine as shown on Reference Manual:
Basically, function to read, send/get ack and switch to master or slave are needed, you just need to follow the flow expressed in this routine or do a polling-specific routine according to your slave’s specifications.
If there is still doubts on I2C routine, you can run I2C example and see on oscilloscope exchanged-data between master and slave.
Hope this can help,
Best Regards,
Isaac
