how-to-i-c-bus.md

How to: I²C Bus

This is the main bus BigClown uses to communicate with the most of the sensors and modules. All sensors and modules have their own addres in the BigClown I²C address space.

Normally you don't need to use I²C API, because all the sensors have their own libraries that gives you the measured data. You will need I²C APIs in case you implement your own I²C sensor or chip.

{% hint style="info" %} As always...
... all available SDK functions for I²C can be found in the SDK documentation. {% endhint %}

I²C buses on the Core Module

There are two busses on the Core Module. They are called:

• BC_I2C_I2C0 - Using SDA0 and SCL0 (17, 18) pins in the bottom right corner of the Core Module
• BC_I2C_I2C1 - Using SDA1 and SCL1 (27, 28) pins in the top right corner of the Core Module

If you use Tag Module then the right three tag connectors use BC_I2C_I2C0 and left three are using BC_I2C_I2C1. You can se this in the schematics.

{% hint style="info" %} There's even a another virtual I2C bus BC_I2C_I2C_1W which is encapsulated in 1-Wire protocol and can be used with Sensor Module and 1-Wire Module to extend the communication distance. {% endhint %}

Init I²C

By default the I²C buses are not initialized to save the power. Hovewer when you initialize at least one sensor in the SDK, the bus is initialized with the first sensor in their respective bc_xxx_init function. If you use only your sensor in the project, you have to initialize the I²C bus.

bc_i2c_init(BC_I2C_I2C0, BC_I2C_SPEED_400_KHZ);

Reading and writing 8 or 16 bits

You can use functions to write or read 1 byte, 2 bytes or specific number of bytes which is explained in next chapter below.

bool bc_i2c_memory_write_8b (bc_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint8_t data)
bool bc_i2c_memory_write_16b (bc_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint16_t data)

bool bc_i2c_memory_read_8b (bc_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint8_t *data)
bool bc_i2c_memory_read_16b (bc_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint16_t *data)

For example to write the data

bc_i2c_memory_write_8b(BC_I2C_I2C0, 0x48, 0x01, 0x81);
bc_i2c_memory_write_16b(BC_I2C_I2C0, 0x48, 0x01, 0x0180);

To read the data

uint8_t reg_configuration;
bc_i2c_memory_read_8b(BC_I2C_I2C0, 0x48, 0x01, &reg_configuration);

Reading and writing more data

bool bc_i2c_write (bc_i2c_channel_t channel, const bc_i2c_transfer_t *transfer)
bool bc_i2c_read (bc_i2c_channel_t channel, const bc_i2c_transfer_t *transfer)

Example to read more data:

bc_i2c_memory_transfer_t transfer;
uint8_t rx_buffer[6];

transfer.device_address = 0x48;
transfer.memory_address = 0x28;
transfer.buffer = rx_buffer;
transfer.length = sizeof(rx_buffer);

bc_i2c_memory_read(BC_I2C_I2C0, &transfer);