ESP32-S3 PDA

A simple ESP32-S3 based phone companion and pocket computer. This open-source hardware project includes a custom PCB, 3D-printable case, and Arduino firmware — everything you need to build a portable device with a color TFT display, LiPo battery management, and physical navigation buttons.

Features

• ESP32-S3-WROOM-1-N16R8 module (16 MB flash, 8 MB PSRAM)
• ST7789 240×320 TFT color display with PWM backlight control
• MAX17048 LiPo fuel gauge for accurate battery state-of-charge
• MCP73831 Li-Ion/Li-Po battery charger (charges via USB)
• WS2812/NeoPixel RGB status LED
• 3 navigation buttons (UP, SELECT, DOWN) with active-low pull-ups
• USB micro-B connector for power and data
• 2-layer PCB with Gerber files ready for fabrication
• 3D-printable case designed in FreeCAD

Pinout

Silkscreen	GPIO	Function
SCL	2	SPI SCLK (TFT clock)
SDA	1	SPI MOSI (TFT data)
CS	3	TFT chip select
DC	4	TFT data/command
RST	5	TFT reset
BL	6	TFT backlight PWM
—	7	WS2812 status LED (NeoPixel)
—	8	I2C SCL (MAX17048 fuel gauge)
—	9	I2C SDA (MAX17048 fuel gauge)
—	10	Button UP
—	11	Button SELECT
—	12	Button DOWN

Display connector: 1×08 pin header (GND, VCC, SCL, SDA, RST, DC, CS, BL) for ST7789 240×320 TFT, 1.54″ or 1.69″ diagonal.

I²C address: MAX17048 at 0x36.

Bill of Materials

Reference	Qty	Part	DigiKey P/N	Description	Price
J1	1	RAHMB20AUETR	137-RAHMB20AUETRCT-ND	USB micro-B receptacle, right-angle, SMT (Switchcraft)
LED1	1	COM-16347	568-16347CT-ND	WS2812/NeoPixel RGB LED
R1, R2	2	RC1206FR-132KL	13-RC1206FR-132KLCT-ND	2 kΩ 1206 thick-film resistor (Yageo)
SW1, SW2, SW3, SW4	4	B3F-1002	SW401-ND	Tactile switch (Omron)
U1	1	ESP32-S3-WROOM-1-N16R8	5407-ESP32-S3-WROOM-1-N16R8CT-ND	ESP32-S3 module, 16 MB flash, 8 MB PSRAM
U2	1	MCP73831T-2DCI/MC	MCP73831T-2DCI/MCCT-ND	Li-Ion/Li-Po battery charger IC (Microchip)
U3	1	TPS74533PCQWDRVRQ1	296-TPS74533PCQWDRVRQ1CT-ND	3.3 V LDO voltage regulator, 500 mA (TI)
U4	1	MAX17048G+T10	MAX17048G+T10CT-ND	LiPo fuel gauge IC (Maxim Integrated)
U5	1	AO3400A	785-1000-1-ND	N-channel MOSFET, SOT-23 (battery protection)
—	1	Custom PCB & stencil	JLCPCB	Fabrication	$20.00
—	1	DigiKey components		Components & shipping	$30.00
—	1	1Ah battery		https://www.amazon.com/dp/B0DPZVBKMY?th=1	$8.00
—	1	Display		https://www.amazon.com/gp/product/B0DFWLD38D/ref=ox_sc_act_title_2?smid=A2UYBS1CH53PM5	$16.00

Pictures

## Power Architecture

USB VBUS (5 V)
  ├── MCP73831 charger (U2) ──→ VBAT (battery voltage)
  │     ├── AO3400A MOSFET (U5) — battery protection
  │     └── MAX17048 fuel gauge (U4) — I²C monitoring
  │
  └── TPS74533 LDO (U3) ──→ 3.3 V rail
        ├── ESP32-S3 module (U1)
        ├── Display backlight (PWM on GPIO6)
        └── Peripherals (WS2812, buttons, I²C pull-ups)

• The device charges a single-cell LiPo battery via USB at 4.2 V termination.
• Battery voltage and state-of-charge are monitored by the MAX17048 over I²C.
• The 3.3 V LDO powers the MCU and peripherals from either USB or battery.

Repository Structure

PDA/
├── README.md              # This file
├── BOM.csv                # Bill of Materials with DigiKey part numbers
├── Journal.md             # Design journal — case design notes & images
├── LICENSE                # MIT License
│
├── board/                 # KiCad PCB design
│   ├── board.kicad_sch    # Schematic
│   ├── board.kicad_pcb    # PCB layout
│   ├── board.kicad_pro    # Project settings
│   ├── gbrs/              # Gerber files (ready for fabrication)
│   └── staging/           # Vendor symbols, footprints, and 3D models
│
├── CAD/                   # FreeCAD mechanical design
│   ├── Assembly.FCStd     # Full assembly (PCB + case + battery + display)
│   ├── case.FCStd         # 3D-printable enclosure
│   ├── battery.FCStd      # Dummy battery model (fit check)
│   ├── display.FCStd      # Dummy display model (fit check)
│   └── PCB.step           # PCB STEP export
│
└── CODE/                  # Firmware
    └── test/
        ├── platformio.ini # PlatformIO build configuration
        └── src/
            └── main.cpp   # Arduino demo sketch

Firmware

The demo firmware exercises all major subsystems: display, battery gauge, status LED, and buttons.

Build & Flash

Prerequisites: PlatformIO (VS Code extension or CLI).

cd CODE/test

# Build
pio run

# Flash and open serial monitor (115200 baud)
pio run --target upload --target monitor

What the Demo Does

1. Boot splash — "ESP32-S3 PDA / Boot OK" on the TFT, WS2812 glows blue
2. Battery readout — cell voltage and state-of-charge, updates ~6× per second
3. Button indicators — shows pressed button (UP/SELECT/DOWN) on the TFT
4. LED feedback — WS2812 colour changes:
   • Purple = idle
   • Green = SELECT
   • Red = UP
   • Blue = DOWN
5. Serial debug — prints voltage, SOC, and button state at 115200 baud

Libraries

Library	Version
Adafruit GFX	≥1.11
Adafruit ST7735/ST7789	≥1.10
Adafruit MAX1704X	≥1.0
FastLED	≥3.7

All are fetched automatically by PlatformIO via lib_deps.

Board Configuration

Setting	Value
Board	ESP32-S3 DevKitC-1
Framework	Arduino
Monitor baud	115200

Customisation

• Backlight level — call backlightWrite(0..255) in loop() (e.g., dim after inactivity)
• Rotation — change tft.setRotation(1) (0–3) if your panel is mounted differently
• I²C pins — edit I2C_SDA and I2C_SCL at the top of main.cpp

PCB

• Layers: 2-layer board
• Software: KiCad 8
• Gerber files: Ready for fabrication in board/gbrs/
• View online: Kicanvas — interactive board viewer (no KiCad install needed)

The PCB uses all surface-mount components. Most ICs are in small-outline packages (SOT-23, TDFN, WSON). The display connects via a standard 1×08 2.54 mm pitch pin header.

Case

Designed in FreeCAD with a boxy, sharp-edged aesthetic. The case holds:

• The custom PCB
• A single-cell LiPo battery
• The ST7789 TFT display (1.54″ or 1.69″)

Dummy battery and display models are included for fit checking in the assembly.

License

MIT License — see LICENSE for details.

Copyright (c) 2026 jacobjuneau6