Dual Board I2C Slave

Materials

Example

I2C Introduction

There are two roles in the operation of I2C, one is “master”, the other is “slave”. Only one master is allowed and can be connected to many slaves. Each slave has its unique address, which is used in the communication between master and the slave. I2C uses two pins, one is for data transmission (SDA), the other is for the clock (SCL). Master uses the SCL to inform slave of the upcoming data transmission, and the data is transmitted through SDA. The I2C example was named “Wire” in the Arduino example.

Introduction

In this example, two AMB82-mini boards communicate with each other over I2C. One board is configured as the I2C slave at address 0x08, and the other as the I2C master. The slave listens for 127 bytes sent by the master via an onReceive callback, verifies the received data, then sends 127 bytes back to the master via an onRequest callback. This example demonstrates full two-way I2C communication between two Ameba boards from the slave’s perspective.

This example uses the I2CSlave_dual sketch on the slave board, paired with the I2CMaster_dual sketch on the master board. Refer to Dual Board I2C Master for the full hardware setup and wiring.

Procedure

  • Setting up the Slave Board

Make sure to choose your AMB82-mini development board in the IDE Tools -> Board
Open the “I2C Slave Dual” example in File -> Examples -> AmebaWire -> I2CSlave_dual

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Click Sketch -> Upload to compile and upload the example to the slave AMB82-mini.

  • Setting up the Master Board

Open another window of Arduino IDE and select the master AMB82-mini’s port in Tools -> Port
Open the “I2C Master Dual” example in File -> Examples -> AmebaWire -> I2CMaster_dual

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Click Sketch -> Upload to compile and upload the example to the master AMB82-mini.

  • Wiring

Connect the SDA pin (pin 12) of the master AMB82-mini to the SDA pin (pin 12) of the slave AMB82-mini with a pull-up resistor (3.3V).
Connect the SCL pin (pin 13) of the master AMB82-mini to the SCL pin (pin 13) of the slave AMB82-mini with a pull-up resistor (3.3V).
Connect the GND pins of both boards together.
Press the reset button on the slave board first to initialize it. Then press the reset button on the master board.
Open the Serial Monitor of the slave AMB82-mini in Tools -> Serial Monitor.
The slave will print the data received from the master and show the verification result (“Result is success” or “Result is fail”). It will also confirm when it has sent the response data back to the master.

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Code Reference

Use Wire.begin(address) to join the I2C bus as a slave with the given address.
https://www.arduino.cc/en/Reference/WireBegin
Use Wire.onReceive(handler) to register a callback function that is called when the slave receives data from the master.
https://www.arduino.cc/en/Reference/WireOnReceive
Use Wire.onRequest(handler) to register a callback function that is called when the master requests data from this slave.
https://www.arduino.cc/en/Reference/WireOnRequest
Use Wire.available() and Wire.read() to read bytes received from the master inside the receive callback.
https://www.arduino.cc/en/Reference/WireAvailable
Use Wire.write() to queue data to be sent to the master inside the request callback.
https://www.arduino.cc/en/Reference/WireWrite
Use Wire.slaveReadLen() to set the expected number of bytes to read from the master.
Use Wire.slaveWrite() to trigger the slave to prepare and send the queued data to the master.