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UM PROS3
An advanced ESP32-S3 board by Unexpected Maker, featuring ESD protection, castellated headers, and extensive Flash and PSRAM, suitable for professional applications.
53 × 17.8 mm
ESP32-S3
MCU
240MHz
clock
16MB
flash
512KB
SRAM
24· 14 ADC
GPIO
BLE 5.0+ WiFi
radio
Pinout
24 pins · 2.54 mm pitch
| Pin | GPIO | Labels | Status | Capabilities | Notes |
|---|---|---|---|---|---|
| 1 | 1 | A0T1PWM | safe | adc · touch | |
| 2 | 2 | A1T2PWM | safe | adc · touch | |
| 3 | 3 | A2T3PWM | strapping | adc · touch | |
| 4 | 4 | A3T4PWM | safe | adc · touch | |
| 5 | 5 | A4T5PWM | safe | adc · touch | |
| 6 | 6 | A5T6PWM | safe | adc · touch | |
| 7 | 7 | A6T7PWM | safe | adc · touch | |
| 8 | 8 | SDAA7T8PWM | safe | adc · touch · i2c | |
| 9 | 9 | SCLA8T9PWM | strapping | adc · touch · i2c | |
| 10 | 10 | VBAT_SENSEPWM | strapping | - | |
| 11 | 12 | A11T12PWM | strapping | adc · touch | |
| 12 | 13 | A12T13PWM | strapping | adc · touch | |
| 13 | 14 | A13T14PWM | strapping | adc · touch | |
| 14 | 15 | A14PWM | safe | adc | |
| 15 | 16 | A15PWM | safe | adc | |
| 16 | 17 | RGB_PWRLDO2PWM | safe | - | |
| 17 | 18 | RGB_DATAPWM | safe | - | |
| 18 | 33 | VBUS_SENSEPWM | strapping | - | |
| 19 | 34 | SSPWM | strapping | spi | |
| 20 | 35 | MOSISDOPWM | strapping | spi | |
| 21 | 36 | SCKPWM | strapping | spi | |
| 22 | 37 | MISOSDIPWM | strapping | spi | |
| 23 | 43 | TXPWM | strapping | uart | |
| 24 | 44 | RXPWM | strapping | uart |
Start with these
11 pins with no boot or system involvementA0T1A1T2A3T4A4T5A5T6A6T7SDAA7A14PWMA15PWMRGB_PWRLDO2RGB_DATAPWM
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 |
|---|---|---|---|
| A2 | 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 |
| 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 |
|---|---|---|---|
| SCL | 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 |
| VBAT_SENSE | FSPICS0 | Used to select the external flash chip. It is required for flash access and cannot be repurposed without losing flash connectivity | Flash |
| A11 | FSPICLK | Drives the flash (and PSRAM) clock. This critical signal must be reserved for memory and not used as general GPIO. | Flash |
| A12 | FSPIQ | Used as a data line for flash/PSRAM transfers. Not available for other uses when flash/PSRAM is connected. | Flash |
| A13 | FSPIWP | Connected to external flash (data/write-protect signal). Not recommended as GPIO because it’s reserved for flash operations. | Flash |
| VBUS_SENSE | 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 |
| SS | FSPICS0 | Wired to the chip select of the internal flash in flash-equipped variants. It must remain low during flash operation, so it’s not available for other use. | Flash |
| MOSI | FSPID / PSRAM_D0 | In modules with octal PSRAM, this pin is connected to the PSRAM data line. It is reserved for memory interface and not free for general GPIO when flash/PSRAM is present. | Flash |
| SCK | 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 |
| MISO | 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 |
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 UM PROS3 are usable GPIO, spaced at the standard 2.54 mm pitch. Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO8 and SCL…
All 24 pins on the UM PROS3 are usable GPIO, spaced at the standard 2.54 mm pitch.
Peripheral wiring is straightforward: I²C is mapped to SDA on GPIO8 and SCL on GPIO9; the SPI bus (MOSI, MISO, SCK, SS) is broken out in full; TX/RX on GPIO43 and GPIO44 cover serial logging and flashing.
Beyond plain digital I/O you get 14 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 (A2, TX and RX) - check the guidance above before wiring anything to them. A0, A1, A3, A4 and 7 more are free of any such role - the safest first picks.
Getting started
flash your first firmware in ~2 minutes1
Connect over USB
Native USB - no driver, no serial chip. Not detected? Hold BOOT while plugging in.
2
Flash with your tool
Arduino IDE, PlatformIO, ESPHome or esptool - copy the settings on the right.
3
Verify it runs
The blink example uses GPIO1 - swap for your board's LED pin if different.
Board: Pros3
USB CDC On Boot: Enabled
Flash Size: 16MB · QIO
Upload Speed: 921600
// blink
pinMode(1, OUTPUT);
digitalWrite(1, LOW); // on (often inverted)[env:pros3]
platform = espressif32
board = esp32-s3-devkitc-1
framework = arduino
monitor_speed = 115200
upload_speed = 921600esp32:
board: esp32-s3-devkitc-1
variant: um_pros3
framework:
type: esp-idf
# blink - GPIO1
output:
- platform: gpio
pin: 1
id: led_out
light:
- platform: binary
name: "LED"
output: led_outesptool.py --chip esp32s3 --port /dev/ttyACM0 \
write_flash 0x0 firmware.binBuild details: sketch space 1310720 B · data 327680 B · QIO
Specifications
ESP32-S3 · 53 × 17.8 mmCompute
MCU
ESP32-S3
Clock
240 MHz
SRAM · Flash
512 KB · 16MB · 8MB (QSPI) PSRAM
Radio
Wi-Fi
802.11 b/g/n
Bluetooth
5.0 LE
Antenna
3D
I/O
GPIO · ADC
24 · 14
UART · I²C · SPI
3 · 2 · 4
PWM
8 channels
Power
USB
USB-C
Serial
Native (CDC)
Boot address
0x0
Flashing
Upload · OTA
esptool_py · esp_ota
Flash · Boot mode
QIO · QIO
Sketch · Data
1.25 MB · 320 KB
53 × 17.8 mm · pin pitch 2.54 mm
The UM PROS3 uses esptool_py for firmware uploads, esp_ota for over-the-air (OTA) updates. Flash mode is QIO with QIO boot mode. The maximum sketch size is 1.25 MB with 320 KB available for data.
About this board
Inside sits the ESP32-S3 - a dual-core Xtensa with vector extensions suited to AI workloads.
The $29.95 price tag is typical for an ESP32-S3 board.
Around the module: 8MB (QSPI) PSRAM, a STEMMA QT connector, an addressable RGB LED (GPIO18), battery charging (TP4065) via PicoBlade, status LEDs (Power, Charge) and Reset/Boot buttons.
It flashes over native USB - no serial-converter driver needed, which isn't a given among ESP32-S3 boards.
- USB-C with back-feed protection
- USB ESD protection (USBLC6-2P6)
- Dual 700mA 3.3V LDO regulators (NCP167); LDO2 user-controlled, auto-shuts down in deep sleep
- 3D high-gain (Fractus) chip antenna
- STEMMA QT / Qwiic powered from LDO1
- Castellated edge + through-hole headers
- LiPo charging ~330mA via TP4065
Where to buy
prices are typical street pricesUM PROS3
$29.95per unit, typical
Resources
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