unPhone 9

by unPhone

An advanced version of the unPhone series, featuring ESP32-S3 and enhanced communication capabilities.

USB-C Native USB

Buy · $148.00 Pinout

ESP32-S3

MCU

240MHz

clock

8MB

flash

512KB

SRAM

25· 18 ADC

GPIO

BLE 5.0+ WiFi

radio

Pinout

25 pins

View:

Pin	GPIO	Labels	Status	Capabilities
1	1	A0PWM	safe	adc
2	2	A1T1PWM	safe	adc · touch
3	3	SDAPWM	strapping	i2c
4	4	SCLPWM	safe	i2c
5	5	A4T4PWM	safe	adc · touch
6	6	A5T5PWM	safe	adc · touch
7	7	A7T7PWM	safe	adc · touch
8	8	A2T2PWM	safe	adc · touch
9	9	A3T3PWM	strapping	adc · touch
10	12	A11T11PWM	strapping	adc · touch
11	13	LED_BUILTINSSA12T12PWM	strapping	adc · touch · spi
12	14	A6A13T6T13PWM	strapping	adc · touch
13	15	A8A14T8T14PWM	safe	adc · touch
14	16	A15PWM	safe	adc
15	17	A16PWM	safe	adc
16	18	A17PWM	safe	adc
17	19	A18PWM	uart	adc
18	20	A19PWM	uart	adc
19	27	A10T10PWM	safe	adc · touch
20	33	A9T9PWM	strapping	adc · touch
21	39	SCKPWM	strapping	spi
22	40	MOSIPWM	strapping	spi
23	41	MISOPWM	strapping	spi
24	43	TXPWM	strapping	uart
25	44	RXPWM	strapping	uart

Start with these

12 pins with no boot or system involvement

A0PWMA1T1SCLPWMA4T4A5T5A7T7A2T2A8A14A15PWMA16PWMA17PWMA10T10

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
SDA	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
SCK	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
MOSI	MTDO (GPIO40)	Default JTAG TDO output for debugging. Using it as GPIO will interfere with JTAG debugging functionality.	Other
MISO	MTDI (GPIO41)	Default JTAG TDI input for debugging. Should be reserved for JTAG or left unused if JTAG is to remain available.	Other
TX	U0TXD (GPIO43)	Used for bootloader output and UART console logs. If repurposed, you will lose the default serial output (and programming via UART0).	Other
RX	U0RXD (GPIO44)	Used for bootloader input (download mode via serial). If repurposed, you cannot use the default UART0 download mode for programming the chip.	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

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 The unPhone 9 pinout brings out 25 GPIO pins - every one of them usable in your project. For peripherals, I²C is mapped to SDA on GPIO3 and SCL on GPIO4; the…

The unPhone 9 pinout brings out 25 GPIO pins - every one of them usable in your project.

For peripherals, I²C is mapped to SDA on GPIO3 and SCL on GPIO4; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.

On the analog side there are 18 ADC-capable pins for sensors and battery monitoring and 12 capacitive-touch inputs.

If you want zero surprises, A0, A1, SCL, A4 and 8 more are free of any such role - the safest first picks. 6 of the exposed pins carry boot-time or system duties on the ESP32-S3 (SDA, SCK, MOSI and 3 more).

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:unphone9]
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: unphone9
  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 8716288 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

25 · 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 · 8.31 MB

The unPhone 9 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 8.31 MB available for data.

About this board

At its core is the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.

Expect to pay about $148.00 - above the ~$30 typical for ESP32-S3 boards.

Onboard you'll find 8MB (QSPI) PSRAM, a TFT 3.5" 320x480 display with touch, a microSD slot, LoRa (RFM95W), an LSM6DS3TR-C 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 To-Do LEDs)
Hardware power on/off switch
Bundled backplane with two FeatherWing sockets & prototyping area

Where to buy

prices are typical street prices

unPhone 9

$148.00per unit, typical

Resources

ESP32-S3 datasheet espressif.com↗ unPhone project site & hardware docs unphone.net↗unPhone Arduino library (GitLab) gitlab.com↗unPhone spin 9 schematic (PDF) gitlab.com↗

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