Haptic controller copy

Haptic Motor Controller PCB

A custom PCB that independently drives up to 16 haptic motors via I2C, with an LED status grid. Designed in KiCad as a first PCB project, with future use as a haptic feedback interface for robot teleoperation.

Architecture

USB-C 5V
  |
  +---> 5V Motor Rail ---> DRV2605L x8 ---> ERM Motors x8
  |
  +---> AP2112K LDO ---> 3.3V Logic Rail
                            |
                            +---> ESP32-S3-WROOM-1 (MCU)
                            +---> TCA9548A (I2C Mux, 8-channel)
                            +---> 74HC595 x2 (LED shift registers)
                            +---> 16x Status LEDs

How it works

1. MCU sends I2C commands to the TCA9548A mux to select a channel (0-7)
2. Each channel connects to one DRV2605L haptic driver (all share address 0x5A, but the mux isolates them)
3. Each DRV2605L drives one ERM coin motor using its built-in H-bridge and 123-effect waveform library
4. 74HC595 shift registers drive 16 status LEDs using only 3 GPIO pins
5. Power: USB-C 5V feeds motors directly, AP2112K LDO drops to 3.3V for logic

Bill of Materials (Estimate ~$30-35)

Key Design Decisions

• ERM over LRA motors: cheaper ($0.40 vs $2+), more forgiving, better LCSC availability
• TCA9548A mux: solves the fixed-address DRV2605L problem (all 0x5A)
• 74HC595 for LEDs: uses only 3 GPIO pins for 16 LEDs, vs burning 16 GPIOs
• ESP32-S3 module: Wi-Fi/BLE for wireless control, large GPIO count, good KiCad libraries
• 2-layer PCB: simpler and cheaper for a first board (4-layer if needed later)

Project Phases

Phase 1: Learn KiCad (1-2 days)

• Install KiCad 9
• Complete the official "Getting Started" tutorial (simple board with LED + resistor)
• Learn: schematic editor, footprint assignment, PCB editor, DRC

Phase 2: Schematic Design (3-5 days)

• Draw the power section (USB-C, LDO, bulk caps)
• Draw the MCU section (ESP32-S3 module, USB, boot/reset buttons)
• Draw the I2C mux + DRV2605L section (one driver first, then replicate x8)
• Draw the LED status grid (74HC595 + LEDs)
• Add decoupling caps to every IC (100nF ceramic, close to VCC/GND)
• Add test points (3.3V, 5V, GND, SDA, SCL)
• Run ERC (Electrical Rules Check), fix all errors

Phase 3: PCB Layout (3-5 days)

• Assign footprints to all components
• Import netlist into PCB editor
• Place components (MCU center, power entry near edge, motors on one side)
• Route critical traces first (power, I2C bus)
• Use wider traces for 5V motor power (0.5mm+)
• Add ground pour on bottom layer
• Run DRC (Design Rule Check), fix all errors
• Review 3D view

Phase 4: Fabrication & Assembly (1-2 weeks)

• Export Gerber files
• Upload to JLCPCB, select 2-layer, standard specs
• Order components from LCSC (can ship with JLCPCB boards)
• Solder components (start with passives, then ICs, then connectors)
• Test power rails first before populating all ICs

Phase 5: Firmware & Testing

• Flash ESP32-S3 with test firmware (Arduino or ESP-IDF)
• Verify I2C mux communication (scan bus for TCA9548A at 0x70)
• Test one DRV2605L channel (play waveform effect)
• Test all 8 channels
• Test LED shift register output
• Write motor control library

Getting Started Right Now

1. Install KiCad

brew install --cask kicad

2. Install useful plugins (after opening KiCad)

• Open Plugin and Content Manager
• Install: Fabrication Toolkit (JLCPCB Gerber export)
• Install: Interactive HTML BOM (visual assembly guide)

3. Get component libraries

• Most parts are in KiCad's built-in library
• For missing parts: download from SnapEDA or Component Search Engine
• Search for: DRV2605L, TCA9548A, ESP32-S3-WROOM-1, AP2112K

4. Start the KiCad tutorial

• Help -> Getting Started with KiCad (built into the app)
• Or: Official Getting Started Guide

Design Rules to Remember

1. Decoupling caps: 100nF ceramic cap as close as possible to every IC's VCC pin
2. I2C pull-ups: ONE set of 4.7k resistors on the upstream bus only (MCU side), NOT on each TCA9548A downstream channel
3. Power traces: 0.5mm+ width for 5V motor rail, 0.25mm is fine for signals
4. Ground plane: pour copper on bottom layer, connected to GND net
5. Test points: add pads for 3.3V, 5V, GND, SDA, SCL for debugging
6. DRC before ordering: fix every error, review every warning

Resources

• KiCad 9 Official Docs
• DRV2605L Datasheet
• TCA9548A Datasheet
• Hardware Design with RP2040 (excellent PCB design reference even if using ESP32)
• JLCPCB Order Guide