Cross compiled I2C

A demo/development platform for software-based I2C protocol.
It can be run on a desktop by starting two instances of the executable that communicate with each other using a JSON file or it can be build and uploaded to run on the AVR/STM32 microcontrollers.
Each target platform is using the same version of the I2C library by compiling the appropriate HAL implementation and has a common console source code for control.

There are scripts for each target platforms that help with deployment under utils/.
The logic analyzer can be used to examine the transmission.

Desktop platform

Create the build-system

cmake -S . -B build-desktop/ -DTARGET_PLATFORM=DESKTOP

Build executable

cmake --build build-desktop/

Run

build-desktop/src/desktop/DesktopDemo

Run Tests

build-desktop/test/Tests

Files generated in the output/ directory such as pins.log, master.log or slave.log can be used by logic analyzer by providing the filenames in the analyzer-properties file.

{
  "logicProbe": { "file": "/path/to/the/pins.log" },
  "loggingProbe": [
    { "name": "Transceiver", "file": "/path/to/the/master.log" },
    { "name": "Receiver", "file": "/path/to/the/slave.log"}
  ],
  "signals": ["SDA", "SCL", "Transmitter SDA", "Transmitter SCL", "Receiver SDA", "Receiver SCL"]
}

AVR platform

Build and upload

cmake -S . -B build-avr/ -DTARGET_PLATFORM=AVR -DCMAKE_TOOLCHAIN_FILE=cmake/avr/avr-toolchain.cmake
cmake --build build-avr/
sudo make -C build-avr/ upload_AvrDemo

Or by using utils/build-avr.sh.

Schematics

The value of $R1$ resistors is calculated to achieve base current $I_B$ sufficient of saturaing BC547 BJTs with the load of I2C bus current $I_C$. The current gain required for saturation is assumed to be $h_{FE}\cdot\frac{1}{10}=10$ and $V_{BE}=0.7V$. $$I_C=\frac{5V}{10k\Omega}=0.5mA$$ $$I_B=\frac{I_C}{h_{FE}\cdot\frac{1}{10}}=0.05mA$$ $$R1 = \frac{V-V_{BE}}{I_B}=86k\Omega$$

STM32 platform

Build and upload

cmake -S . -B build-stm32/ -DTARGET_PLATFORM=STM32 -DCMAKE_TOOLCHAIN_FILE=cmake/stm32/stm32-toolchain.cmake
cmake --build build-stm32/
sudo make -C build-stm32/ Stm32Demo.bin_upload

Or by using utils/build-stm32.sh.

Schematics

Control

Each of the deployments allows for control of the I2C library using the console from src/common/console.c.

Get Commands

These commands are used to retrieve current settings of the I2C configuration.

• get role: Returns the current role of the I2C device (MASTER or SLAVE).
• get address: Returns the current I2C address.
• get time_unit: Returns the current time unit setting.
• get logging_level: Returns the current logging level (0-5).
• get scl: Returns the current level of the SCL pin.
• get sda: Returns the current level of the SDA pin.

Set Commands

These commands are used to set various parameters of the I2C configuration.

• set role [master/slave]: Sets the role of the I2C device.
• set address [0-127]: Sets the I2C address.
• set time_unit [0-1000]: Sets the time unit.
• set logging_level [0-5]: Sets the logging level.
• set scl [0/1]: Sets the SCL_OUT pin level
• set sda [0/1]: Sets the SDA_OUT pin level

Write Commands

These commands are specific to writing operations in I2C communication.

• write byte [0-255]: Writes a byte to I2C.
• write addr [0-127] [r/w]: Writes an address with read or write data direction bit.
• write start: Sends a start condition.
• write stop: Sends a stop condition.
• write to [0-127] [0-255]: Writes to an address with a payload.