unPhone 8

by unPhone

An ESP32-S3 handheld in the unPhone series with a 3.5-inch touchscreen and LoRaWAN radio, for IoT teaching and prototyping.

USB-C Native USB

Pinout

ESP32-S3

MCU

240MHz

clock

8MB

flash

512KB

SRAM

24· 18 ADC

GPIO

BLE 5.0+ WiFi

radio

Pinout

24 pins

View:

Pin	GPIO	Labels	Status	Capabilities
1	1	SDAA0PWM	safe	adc · i2c
2	2	SCLA1T1PWM	safe	adc · touch · i2c
3	3	SSPWM	strapping	spi
4	5	A4T4PWM	safe	adc · touch
5	6	A5T5PWM	safe	adc · touch
6	7	A7T7PWM	safe	adc · touch
7	8	A2T2PWM	safe	adc · touch
8	9	A3T3PWM	strapping	adc · touch
9	12	A11T11PWM	strapping	adc · touch
10	13	LED_BUILTINA12T12PWM	strapping	adc · touch
11	14	A6A13T6T13PWM	strapping	adc · touch
12	15	A8A14T8T14PWM	safe	adc · touch
13	16	A15PWM	safe	adc
14	17	A16PWM	safe	adc
15	18	A17PWM	safe	adc
16	19	A18PWM	uart	adc
17	20	A19PWM	uart	adc
18	27	A10T10PWM	safe	adc · touch
19	33	A9T9PWM	strapping	adc · touch
20	36	RXPWM	strapping	uart
21	37	TXPWM	strapping	uart
22	38	SCKPWM	strapping	spi
23	39	MOSIPWM	strapping	spi
24	40	MISOPWM	strapping	spi

Start with these

11 pins with no boot or system involvement

SDAA0SCLA1A4T4A5T5A7T7A2T2A8A14A15PWMA16PWMA17PWMA10T10

Freely assignable - no strapping, flash, USB or JTAG duties. Ideal first picks for buttons, sensors and LEDs.

Fine - with a little care

sampled at boot or shared with debug/serial

Pin	Label	What to know	Role
SS	GPIO3	Sampled at reset to select JTAG interface (USB Serial/JTAG controller vs. external pins). Improper use can disable external JTAG or alter debug interface.	Strapping
MOSI	MTCK (GPIO39)	Default JTAG debugging TCK pin. If JTAG is needed, this pin must be free; it may also be used internally for PSRAM chip select on certain modules, so avoid repurposing it.	Other
MISO	MTDO (GPIO40)	Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality.	Other

Only if you know the tricks

wired to flash or USB - expect a fight

Pin	Label	What to know	Role
A3	FSPIHD	Connected to external flash (data/hold signal) on most modules. Not recommended for use as GPIO, since it must remain dedicated to flash communication.	Flash
A11	FSPICLK	Drives the flash (and PSRAM) clock. This critical signal must be reserved for memory and not used as general GPIO.	Flash
LED_BUILTIN	FSPIQ	Used as a data line for flash/PSRAM transfers. Not available for other uses when flash/PSRAM is connected.	Flash
A6	FSPIWP	Connected to external flash (data/write-protect signal). Not recommended as GPIO because it’s reserved for flash operations.	Flash
A18	USB_D-	By default connected to the on-chip USB Serial/JTAG controller. Using it as general GPIO without reconfiguring IO MUX will interfere with USB functionality.	USB
A19	USB_D+	By default connected to the on-chip USB Serial/JTAG controller. Using it as general GPIO without reconfiguring IO MUX will interfere with USB functionality.	USB
A9	FSPIHD	On chips/modules with integrated flash, this IO is wired to the flash hold pin internally. It cannot be reassigned to GPIO without breaking flash access.	Flash
RX	FSPICLK / PSRAM_CLK	In modules with octal PSRAM, this pin drives the PSRAM clock. It must be dedicated to the memory interface, not used as a regular GPIO when that interface is in use.	Flash
TX	FSPIQ / PSRAM_DQS	In modules with octal PSRAM, this pin is connected to the PSRAM’s DQS signal. It cannot be repurposed without disrupting the PSRAM/flash communication.	Flash
SCK	FSPIWP	On flash-equipped chips, this pin is tied to the flash’s WP# (or D3) line. It should be avoided for other use, as it’s needed for flash operations.	Flash

These are recommendations, not hard rules - with the right pull-ups, timing and boot-state awareness most pins can be made to work. When in doubt, start green.

Pinout notes All 24 pins on the unPhone 8 are usable GPIO. Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO1 and SCL on GPIO2; the SPI bus ( MOSI , MISO ,…

All 24 pins on the unPhone 8 are usable GPIO.

Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO1 and SCL on GPIO2; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO37 and GPIO36 cover serial logging and flashing.

Beyond plain digital I/O you get 18 ADC-capable pins for sensors and battery monitoring and 12 capacitive-touch inputs.

3 of the exposed pins carry boot-time or system duties on the ESP32-S3 (SS, MOSI and MISO) - check the guidance above before wiring anything to them. SDA, SCL, A4, A5 and 7 more are free of any such role - the safest first picks.

Getting started

flash your first firmware in ~2 minutes

Tool:

Connect over USB

Native USB - shows up as a port right away, no driver needed. Not detected? Hold BOOT while plugging in.

Match & flash

Set the Tools options shown, then click Upload.

Verify it runs

The onboard LED on GPIO1 blinks - swap the pin if your board's LED differs.

Set these in Tools · leave everything else at default

Arduino IDE 2.x — Tools Copy

Board: "ESP32S3 Dev Module"▸

USB CDC On Boot: "Enabled"▸

Flash Size: "8MB (64Mb)"▸

Flash Mode: "DIO"▸

PSRAM: "QSPI PSRAM"▸

Partition Scheme: "8M with spiffs (3MB APP / 1.5MB SPIFFS)" (default)▸

Upload Speed: "921600"▸

▸ every other Tools option — leave at default

Board: ESP32S3 Dev Module
USB CDC On Boot: Enabled
Flash Size: 8MB (64Mb)
Flash Mode: DIO
PSRAM: QSPI PSRAM
Partition Scheme: 8M with spiffs (3MB APP / 1.5MB SPIFFS)
Upload Speed: 921600

Find it: Tools ▸ Board ▸ ESP32 Arduino ▸ ESP32S3 Dev Module

blink.ino Copy

// blink the onboard LED
void setup() {
  pinMode(1, OUTPUT);
}
void loop() {
  digitalWrite(1, HIGH); delay(500);
  digitalWrite(1, LOW);  delay(500);
}

board to selectesp32-s3-devkitc-1⧉ copy

platformio.ini Copy

[env:unphone8]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600
board_build.arduino.memory_type = qio_qspi
build_flags = -DBOARD_HAS_PSRAM

Find it: PlatformIO Home ▸ Boards, search esp32-s3-devkitc-1 — or type it after board =.

board to selectesp32-s3-devkitc-1⧉ copy

device.yaml Copy

esp32:
  board: esp32-s3-devkitc-1
  variant: unphone8
  framework:
    type: esp-idf
psram:
  mode: quad
  speed: 80MHz

# blink - GPIO1
output:
  - platform: gpio
    pin: 1
    id: led_out
light:
  - platform: binary
    name: "LED"
    output: led_out

Find it: search ESPHome's board list for esp32-s3-devkitc-1 (same ids as PlatformIO).

esptool doesn't pick board settings — a prebuilt .bin already has them baked in. This is just the raw flash command.

terminal Copy

esptool.py --chip esp32s3 --port /dev/ttyACM0 \
  --baud 921600 write_flash 0x0 firmware.bin

--port = your /dev/tty* (macOS/Linux) or COMx (Windows).

Build details: sketch space 8323072 B · data 2424832 B · DIO

Specifications

ESP32-S3

Compute

MCU

ESP32-S3

Clock

240 MHz

SRAM · Flash

512 KB · 8MB · 8MB (QSPI) PSRAM

Radio

Wi-Fi

802.11 b/g/n

Bluetooth

5.0 LE

Antenna

PCB

I/O

GPIO · ADC

24 · 18

UART · I²C · SPI

3 · 2 · 4

PWM

8 channels

Power

USB

USB-C

Serial

Native (CDC)

Boot address

0x0

Display

Screen

TFT · 3.5" · 320x480

Driver

HX8357D

Touch

XPT2046

Flashing

Upload · OTA

esptool_py · esp_ota

Flash · Boot mode

DIO · QIO

Sketch · Data

7.94 MB · 2.31 MB

The unPhone 8 uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is DIO with QIO boot mode. The maximum sketch size is 7.94 MB with 2.31 MB available for data.

About this board

Inside sits the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.

Around the module: 8MB (QSPI) PSRAM, a TFT 3.5" 320x480 display with touch, a microSD slot, LoRa (RFM95W), an IMU, an IR transceiver, battery charging (BQ24295) and Button 1/Button 2/Button 3/Reset buttons.

It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S3 boards.

TCA9555 16-bit I²C GPIO expander
Vibration motor
3 discrete indicator LEDs (red / green / blue)
Hardware power on/off switch
Bundled backplane with two FeatherWing sockets & prototyping area

Resources

ESP32-S3 datasheet espressif.com↗ unPhone project site & hardware docs unphone.net↗unPhone Arduino library (GitLab) gitlab.com↗unPhone source & schematics (GitLab) gitlab.com↗

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