I2C Usage Guidelines

• How to Use
• Opening an I2C Controller
• Performing I2C Communication
• Closing an I2C Controller

How to Use

Figure 1 illustrates the process of an I2C device.

Figure 1 Process of using an I2C device

Opening an I2C Controller

Call the following function to open an I2C controller:

DevHandle I2cOpen(int16_t number);

Table 1 Description of I2cOpen

This example assumes that the system has eight I2C controllers (numbered from 0 to 7) and I2C controller 3 is to open.

DevHandle i2cHandle = NULL; /* I2C controller handle */

/* Open an I2C controller. */
i2cHandle = I2cOpen(3);
if (i2cHandle == NULL) {
    HDF_LOGE("I2cOpen: failed\n");
    return;
}

Performing I2C Communication

Use the following function for message transfer:

int32_t I2cTransfer(DevHandle handle, struct I2cMsg *msgs, int16_t count);

Table 2 Description of I2cTransfer

The type of an I2C message transfer is defined by I2cMsg. Each message structure indicates a read or write operation. Multiple read or write operations can be performed by using a message array.

int32_t ret;
uint8_t wbuff[2] = { 0x12, 0x13 };
uint8_t rbuff[2] = { 0 };
struct I2cMsg msgs[2]; /* Custom message array for transfer */
msgs[0].buf = wbuff;    /* Data to write */
msgs[0].len = 2;        /* The length of the data to write is 2. */
msgs[0].addr = 0x5A;    /* The address of the device to write the data is 0x5A. */
msgs[0].flags = 0;      /* The flag is 0, indicating the write operation. */
msgs[1].buf = rbuff;    /* Data to read */
msgs[1].len = 2;        /* The length of the data to read is 2. */
msgs[1].addr = 0x5A;    /* The address of the device to read the data is 0x5A. */
msgs[1].flags = I2C_FLAG_READ /* I2C_FLAG_READ is configured, indicating the read operation. */
/* Perform a custom transfer to transfer two messages. */
ret = I2cTransfer(i2cHandle, msgs, 2);
if (ret != 2) {
    HDF_LOGE("I2cTransfer: failed, ret %d\n", ret);
    return;
}

CAUTION:

• The device address in the I2cMsg structure does not contain the read/write flag bit. The read/write information is transferred by the read/write control bit in the member variable flags.
• The I2cTransfer function does not limit the number of message structures, which is determined by the I2C controller.
• The I2cTransfer function does not limit the data length of each message structure, which is determined by the I2C controller.
• The I2cTransfer function may cause the system to sleep and therefore cannot be invoked in the interrupt context.

Closing an I2C Controller

Call the following function to close the I2C controller after the communication is complete:

void I2cClose(DevHandle handle);

Table 3 Description of I2cClose

I2cClose(i2cHandle); /* Close the I2C controller. */