Jitter

A Raspberry Pi Zero 2 robot control project that interfaces with a PCA9685 16-channel PWM servo driver HAT for precise servo movement control.

Hardware Setup

• Platform: Raspberry Pi Zero 2 running Linux 6.12.25+rpt-rpi-v8
• Servo Controller: PCA9685 16-channel PWM driver at I2C address 0x40
• Active Channels: 7 servo channels (0-6)
• PWM Frequency: 50Hz for servo control
• Pulse Width Range: 500-2500 microseconds (0.5ms to 2.5ms)

Licenses

• Code in this repository is licensed under the MIT License.
• 3D Models in this repository are based on "Makey Dancing Robot of the Maker Faire"
  by OttoDIY, licensed under CC BY-SA 4.0.

Quick Start

Test all servos sequentially:

python /home/jason/Bot/test.py

Architecture

Core Library

The project uses the PCA9685 library located at /home/jason/Bot/example_code/python/PCA9685.py for I2C communication with the servo controller.

Key Methods:

• setPWMFreq(freq): Set PWM frequency (use 50Hz for servos)
• setServoPulse(channel, pulse): Set servo position in microseconds
• setPWM(channel, on, off): Direct PWM control

Movement System

All control scripts use a step-based movement system:

• Servos move in increments (Step0, Step1, Step2, Step3)
• Position limits enforced: 500μs (min) to 2500μs (max)
• Timer-based updates every 20ms for smooth motion
• Center/neutral position: 1500μs

Dependencies

• Python 2.7 or Python 3
• smbus or smbus2 library for I2C communication
• Standard libraries: time, math

Usage

When creating new servo control scripts, import the PCA9685 library:

import sys
sys.path.append('/home/jason/Bot/example_code/python')
from PCA9685 import PCA9685

# Initialize with 50Hz frequency
pwm = PCA9685()
pwm.setPWMFreq(50)

# Set servo position (channel 0 to center position)
pwm.setServoPulse(0, 1500)

Important Notes

• Servo positions are specified in microseconds, not degrees
• Always initialize with 50Hz frequency for standard servo operation
• The robot body has physical constraints - extreme servo positions may cause mechanical issues
• The PCA9685 library exists in both python/ and python3/ directories with identical functionality