I2C Interface¶

Note

I2C a serial interface mainly used to talk to sensors, peripherals and ICs located on the same circuit board as the microcontroller. On Yggdrasil, almost all sensors are connected to it with the ability to connect extra peripherals through the Seeed or PMod connectors.

Simple Usage¶

Reading from and writing to a I2C device is as simple as calling the read and write functions of the relevant I2C interface. For example, for a sensor connected to the Grove A connector, the following code can be used to read data:

const u8 deviceAddress = 0x42;

// Read data directly
u8 value = 0;
yggdrasil_I2C_Read(I2CA, deviceAddress, &value, sizeof(u8));

const u8 registerAddress = 0x11;

// Read data from a register
u8 registerValue = 0;
yggdrasil_I2C_ReadRegister(I2CA, deviceAddress, registerAddress, &registerValue, sizeof(u8));

constexpr u8 DeviceAddress = 0x42;

// Read data directly
auto value = bsp::I2CA::read<u8>(DeviceAddress);

constexpr u8 RegisterAddress = 0x11;

// Read data from a register
auto registerValue = bsp::I2CA::read<u8>(DeviceAddress, RegisterAddress);

And this code to write data:

const u8 deviceAddress = 0x42;

// Write 0xFF directly
u8 value = 0xFF;
yggdrasil_I2C_Write(I2CA, deviceAddress, &value, sizeof(u8));

const u8 registerAddress = 0x22;

// Write 0x55 to a register
value = 0x55;
yggdrasil_I2C_WriteRegister(I2CA, deviceAddress, registerAddress, &value, sizeof(u8));

constexpr u8 DeviceAddress = 0x42;

// Write 0xFF directly
bsp::I2CA::write<u8>(DeviceAddress, 0xFF);

constexpr u8 RegisterAddress = 0x22;

// Write 0x55 to a register
bsp::I2CA::write<u8>(DeviceAddress, RegisterAddress, 0x55);

Important

All I2C interfaces are configured to 100kHz Standard mode. This is the default and works for all on-board peripherals as well as most external peripherals. If a connected peripheral requires a different speed or faster communication is desired, the speed may be changed in the projects .ioc file. However, this can cause the onboard peripherals to no longer be usable.

Available peripherals¶

Peripheral	Bus	Address
PMOD A	I2CA	None
PMOD B	I2CB	None
Grove A	I2CA	None
Grove B	I2CB	None
Raspberry	I2CA & I2CB	None
6 Axis	I2CA	0xD2
Color	I2CA	0x52
Humidity	I2CA	0x88
RTC	I2CA	0xA4
Joystick ADC	I2CA	0x90
Codec	I2CD	0x40
Touch Screen	I2CC	0x54
DCMI	I2CD	None
USB Hub	I2CD	0x58
USB C	I2CD	0x50

Custom I2C¶

In order to control a I2C that has not been pre-defined by libyggdrasil, first it needs to be properly configured through the project’s .ioc file. Once this is done, the new I2C can be defined like this:

i2c_t MyI2C = { &hi2c1 };

using MyI2C = bsp::drv::I2C<&hi2c1, bsp::mid::drv::I2C>;

and then used like all the other I2C.