Exercise A: Bus Scan

~15 min

Goal

Set up an I2C bus on the uFerris board and scan for connected devices.

Steps

1. Create a New Project

esp-generate --chip esp32c3 -o unstable-hal -o vscode -o esp-backtrace -o log --headless i2c_scan
cd i2c_scan

2. Find an I2C Example

Navigate to the esp-hal I2C documentation.

Look for an I2C example in:

• The module-level documentation (esp_hal::i2c)
• The I2c struct page
• The esp-hal examples directory on GitHub

3. Apply the Mental Model

Read the example and identify:

• Instantiate — How is the I2c created? What peripheral and pins does it need?
• Configure — What configuration is applied? (Clock speed, pins)
• Control — What methods are available for reading/writing?

4. Adapt to uFerris

• Check your pinout card for the I2C SDA and SCL pins
• Update the pins in the example to match the uFerris board

5. Scan the Bus

Write a loop that attempts to communicate with every address from 0x01 to 0x7F:

• For each address, try a zero-length write
• If the write succeeds, a device is present at that address
• Print the address of each device found

6. Build and Flash

cargo build --release
espflash flash target/riscv32imc-unknown-none-elf/release/i2c-scan --monitor

What to Notice

• Which addresses respond? Write them down — you'll need them in the next exercise
• One of those addresses is the TCA6424 I/O expander
• Compare the I2C Instantiate pattern to GPIO — what's similar? What's different?