Controlling a Stepper Motor via I2C with the Bus Pirate

1. Introduction

In this experiment, we’ll control a stepper motor using I2C communication through the Bus Pirate. This setup is ideal for sending movement commands and testing motor response.

2. Required Components

• Bus Pirate (v3.6 or later)
• I2C-capable stepper motor driver (e.g., A4988 or L298N with I2C interface)
• Stepper motor (compatible with your motor driver)
• Connecting wires or breadboard
• Computer with terminal software (e.g., PuTTY or Tera Term)

3. Wiring Setup

Connect the Bus Pirate to the stepper motor driver:

• SDA on the Bus Pirate to the SDA on the motor driver
• SCL on the Bus Pirate to the SCL on the motor driver
• GND on the Bus Pirate to the motor driver’s GND
• Ensure proper power connections for the stepper motor and driver

Connect the Bus Pirate to your computer via USB and open a terminal software set to 115200 baud.

4. Initializing I2C Mode on the Bus Pirate

Enter I2C mode by typing:

m 4

Once in I2C mode, configure options by following prompts:

• Speed: Choose a lower speed initially (e.g., 100 kHz) for better stability
• Power and Pull-up Resistors: Enable both if your setup requires

5. Identifying the Stepper Motor Driver I2C Address

Before sending commands, find the I2C address of the stepper motor driver:

(1)

After running this command, the Bus Pirate should display a list of available I2C addresses, identifying the driver’s address for communication.

6. Sending Movement Commands

Use I2C commands to control the stepper motor. Here are some example commands:

Rotate Stepper Motor

To rotate the motor, send a command to the driver’s I2C address (assuming it’s 0x60):

[0x60 0x01 0x10]

This command example sends 0x10 to initiate movement. Commands vary depending on the driver; consult your driver’s documentation for details.

Change Direction

To change the motor’s direction:

[0x60 0x02 0x01]

This command tells the motor to reverse its rotation direction.

Adjust Speed

To adjust speed, try:

[0x60 0x03 0x05]

Here, 0x05 represents the desired speed level.

7. Observing Motor Response

After each command, observe the motor’s behavior to confirm it’s responding correctly. If not:

• Double-check wiring and connections
• Ensure the I2C address matches the motor driver’s address
• Confirm power requirements for the motor and driver

8. Troubleshooting Common Issues

• No Response from Motor: Verify the I2C address and wiring setup. Some drivers may require specific initialization commands.
• Motor Moves Erratically: Ensure power supply is sufficient, and adjust speed settings.
• Address Not Detected: Check for pull-up resistors and try re-scanning the I2C bus.

9. Conclusion

With the Bus Pirate, you can easily control a stepper motor over I2C, enabling you to test and debug I2C-controlled motor drivers.