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How To: I²C Bus

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

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Normally you don’t need to use I²C API, because all the sensors have their libraries in the SDK that gives you the measured data. You will need I²C APIs in case you want to implement a new I²C sensor or chip.

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This chapter goes over some code examples of how to use I²C API. To read more about I²C itself, you can visit I²C Bus chapter.

References

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To start working with I²C you always have to initialize it before you start working with it.

For example twr_i2c_init(TWR_I2C_I2C0, TWR_I2C_SPEED_400_KHZ); will initialize I2C_0 with the speed of 400kHz.

Examples

Read

To read 8 or 16 bits, you can use the built-in SDK functions

bool twr_i2c_memory_read_8b (twr_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint8_t *data)bool twr_i2c_memory_read_16b (twr_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint16_t *data)
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For example, you can read 8 bits of data from memory address 0x01 over I2C_0 from a device with address 0x48 and save the data to the reg_configuration variable.

Read 8 bits over I²C Code Example

uint8_t reg_configuration;twr_i2c_memory_read_8b(TWR_I2C_I2C0, 0x48, 0x01, &reg_configuration);

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To read more data over I²C you have to create a twr_i2c_memory_transfer_t structure.

Read custom number of bits over I²C Code Example

twr_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);twr_i2c_memory_read(TWR_I2C_I2C0, &transfer);

Write

To write 8 or 16 bits, you can use the built-in SDK functions

bool twr_i2c_memory_write_8b (twr_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint8_t data)bool twr_i2c_memory_write_16b (twr_i2c_channel_t channel, uint8_t device_address, uint32_t memory_address, uint16_t data)
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For example, you can write 8 bits, 0x81 to be specific, of data to memory address 0x01 over I2C_0 to a device with address 0x48.

Write 8 bits over I²C Code Example

twr_i2c_memory_write_8b(TWR_I2C_I2C0, 0x48, 0x01, 0x81);

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To write more data over I²C you have to create a twr_i2c_memory_transfer_t structure.

Write custom number of bits over I²C Code Example

twr_i2c_memory_transfer_t transfer;uint8_t tx_buffer[2] = { 0x20, 0x00 };transfer.device_address = 0x48;transfer.memory_address = 0x28;transfer.buffer = tx_buffer;transfer.length = sizeof(tx_buffer);twr_i2c_memory_read(TWR_I2C_I2C0, &transfer);