Comprehensive Pi Servo Hat Setup Guide: Hardware, Wiring, and Python Control

Introduction

The SparkFun Pi Servo Hat expands a Raspberry Pi’s capabilities, allowing you to control up to 16 hobby servos via an I²C bus. By off‑loading servo power and communication to the Hat, you free the Pi’s GPIO pins for other projects and gain a convenient serial terminal for headless setup.

Required Materials

To follow this guide, assemble the following items. We recommend a blank microSD card rather than a NOOBS card, as newer OS images are required for Pi Zero W support.

Break Away Headers – Straight

Wall Adapter Power Supply – 5.1V DC 2.5A (USB Micro‑B)

microSD Card with Adapter – 16GB (Class 10)

Raspberry Pi GPIO Tall Header – 2×20

Raspberry Pi Zero W

SparkFun Pi Servo HAT

Finally, acquire a hobby servo for testing. A generic sub‑micro servo is a good starting point for the example scripts.

Servo – Generic (Sub‑Micro Size)

Required Tools

No special equipment is needed beyond basic soldering supplies. For best results, use a 30W soldering iron and lead‑free solder.

Solder Lead Free – 15‑gram Tube

Soldering Iron – 30W (US, 110V)

Hardware Overview

The Hat is intentionally simple. Key components include:

• USB Micro‑B Connector – Supplies 5 V to the servos and can also power the Pi. It also provides a serial console that lets you configure the Pi without a monitor.
• Power‑Isolation Jumper – Closed by default, connecting the servo rail to the Pi’s 5 V rail. Clear it when you run multiple high‑current servos to prevent noise from resetting the Pi.
• Servo Headers – 16 0.1‑inch spaced pins, pre‑arranged for standard hobby servo connectors.

Hardware Assembly

We recommend soldering the male headers onto the Pi Zero W first, then attaching the Pi Servo Hat. A quick technique:

1. Solder a single pin to the board.
2. While the solder is still hot, tilt the board so the pin sits flat, then secure the header in place.
3. Finish soldering the remaining pins.

Repeat the process with the female header and the Pi Servo Hat, ensuring the short pins insert from the bottom of the board. Keep the headers level before completing the solder joints.

Once assembled, stack the Hat on the Pi Zero W. Connect a hobby servo to channel 0, referencing the servo’s datasheet for pinout. Use a 5 V wall adapter to power the Pi and the Hat via the USB Micro‑B connector labeled PWR IN.

Software – Python

The Hat’s PWM controller is an I²C device, commonly accessed as SMBus. Full example code is available in the product’s GitHub repository.

Initialize SMBus

import smbus
bus = smbus.SMBus(1)  # I2C bus 1 on Raspberry Pi
addr = 0x40          # Default I2C address of the PWM chip

Configure the PWM Chip

bus.write_byte_data(addr, 0x00, 0x20)   # Enable PWM module
bus.write_byte_data(addr, 0xFE, 0x1E)   # Auto‑increment register addresses

Set a Pulse Width for Channel 0

bus.write_word_data(addr, 0x06, 0)     # Start time (always 0 for 200 Hz)
bus.write_word_data(addr, 0x08, 1250)  # Stop time → 1.5 ms pulse

The PWM chip runs at 200 Hz (5 ms period). The stop register (0–4095) maps to 1.2 µs steps, so 1250 ≈ 1.5 ms, the neutral position for most servos.

To address other channels, add 4 to the register addresses:

Channel	Start Addr	Stop Addr
0	0x06	0x08
1	0x0A	0x0C
2	0x0E	0x10
3	0x12	0x14
4	0x16	0x18
5	0x1A	0x1C
6	0x1E	0x20
7	0x22	0x24
8	0x26	0x28
9	0x2A	0x2C
10	0x2E	0x30
11	0x32	0x34
12	0x36	0x38
13	0x3A	0x3C
14	0x3E	0x40
15	0x42	0x44

Each degree of movement requires 4.6 register counts. For example, a 45° offset from neutral is 207 counts (45 × 4.6), added or subtracted from 1250 to set the desired pulse width.

For more detailed examples, visit the GitHub repo and explore the included Python scripts.

Pi Servo Hat Hookup Guide