ESP32-S3 Expansion Base pinout

InteractiveOpen the S3 Expansion in 3DTurn the real board over and click any of its 40 holes. Every pad is placed from this design’s own net list.Open in 3D →

Reading this board

The base has no chip and nothing active on it. An ESP32-S3 Gold Edition plugs into the two sockets down the middle, antenna end toward the display connector, and the base brings most of its pins out along both edges. Each edge has two 20-way strips side by side on the same nets, hole for hole, so there are 80 holes in 40 positions: 28 GPIOs, plus 3V3, 5V and GND repeated along the way.

The order is the S3 Gold's own, read from this design's net list, so anything that is true of a pin on the S3 Gold pinout is true of the same pin here. Open the base in 3D and click either strip; the handbook covers using it.

What the edge carries

Edge	Top to bottom, display end first
Left	3V3, GND, 4, 5, 6, 7, 15, 16, 17, 18, 8, 3, 9, 10, 11, 12, 13, 14, GND, 3V3
Right	3V3, 5V, GND, GND, 1, 2, 42, 41, 40, 39, 38, 48, 47, 21, 20, 19, GND, GND, 5V, 3V3

That is 16 GPIOs on the left and 12 on the right. 5V is on the right strips only, at the second and second-last holes; the left has none.

The eight that stay on the sockets

A strip is 20 holes and a socket is 22, and the dev board has 36 GPIOs, so some do not come out. These eight go to the sockets and no further: GPIO0, 35, 36, 37, 43, 44, 45 and 46. RST stays on the socket as well.

GPIO	Why you would not have wanted it
35, 36, 37	Octal PSRAM on the N16R8 module the kit ships. Driving one crashes the board.
43, 44	The serial link to the USB-serial chip.
0, 45, 46	Strapping pins, read at reset to decide how the chip boots.

Everything else on the dev board's edge is on a strip. GPIO19 and 20 are the native USB lines and GPIO3 is a strapping pin that floats by default; they are there if you want them, with those facts attached.

The marks and the back

The top silkscreen prints ~, # and ^ beside some numbers. The back repeats them as boxes: ADC1 over 3 to 10, I2S over SCL 9 and SDA 8, UART TX 43 and RX 44, SPI MOSI 11, MISO 13, SCK 12, SS 10, and USB D− 19, D+ 20. The I2S box means I²C; nothing on this board touches I²S. 43 and 44 are on the back's UART box but are not brought out to a strip.

The display connector

A 15-way FPC socket on a 1.0 mm pitch at the top of the board. Nothing switches its lines: all thirteen signals are the same nets as holes on the strips, so a fitted display owns those GPIOs.

Contact	Signal	Contact	Signal
1	GND	9	GPIO10
2	3V3	10	GPIO1
3	GPIO41	11	GPIO15
4	GPIO42	12	GPIO7
5	GPIO2	13	GPIO4
6	GPIO13	14	GPIO6
7	GPIO12	15	GPIO5
8	GPIO11

The net list names those lines BL, DC and CS for GPIO41, GPIO2 and GPIO10, and D2 to D7 for GPIO1, 15, 7, 4, 6 and 5. The back of the board prints contacts 10 and 11 as 20-1 and 22-15; there is no contact 20 or 22 on a 15-way connector, so that is a typo in the legend and the wiring above is right.

Power

3V3 and 5V are the S3 Gold's own pins passed straight through; the base has no regulator. 3V3 comes from the S3 Gold's AMS1117 and there is a 3V3 hole at both ends of every strip. 5V is the dev board's 5V pin, which on USB power is the cable's 5 V less a diode drop. All the GND holes are the same net.

Pins to leave alone

GPIO15 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO16 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO17 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO18 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO3 — Strapping pin. Selects the JTAG source. Floating at reset is the normal state.
GPIO11 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO12 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO13 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO14 — ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO48 — WS2812B RGB LED, single-wire at 800 kHz. The silkscreen says RGB@IO48.
GPIO20 — Native USB-C, D+ . Wired straight to the USB-Serial-JTAG peripheral, no bridge chip in the path.
GPIO19 — Native USB-C, D− . Wired straight to the USB-Serial-JTAG peripheral, no bridge chip in the path.

Every pin

Pin	Name	Functions	Notes
3V3	3.3 V rail	power	L1. Output of the on-board regulator. Everything on the board runs from it, so budget what the regulator can spare, not what USB can deliver. A steady 3.3 V supply can also power the board through it, but never with USB plugged in at the same time.
GND	Ground	power	L2. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GPIO4	GPIO4	gpio, adc1, touch	L3
GPIO5	GPIO5	gpio, adc1, touch	L4
GPIO6	GPIO6	gpio, adc1, touch	L5
GPIO7	GPIO7	gpio, adc1, touch	L6
GPIO15	GPIO15	gpio, adc2	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO16	GPIO16	gpio, adc2	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO17	GPIO17	gpio, adc2, uart	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO18	GPIO18	gpio, adc2, uart	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO8	GPIO8	gpio, adc1, touch, i2c	L11. Arduino default: Wire (I²C) SDA.
GPIO3	GPIO3	gpio, adc1, touch	Strapping pin. Selects the JTAG source. Floating at reset is the normal state.
GPIO9	GPIO9	gpio, adc1, touch, i2c	L13. Arduino default: Wire (I²C) SCL.
GPIO10	GPIO10	gpio, adc1, touch, spi	L14. Arduino default: SPI (HSPI) SS.
GPIO11	GPIO11	gpio, adc2, touch, spi	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO12	GPIO12	gpio, adc2, touch, spi	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO13	GPIO13	gpio, adc2, touch, spi	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GPIO14	GPIO14	gpio, adc2, touch	ADC2, so analogRead stops working the moment Wi-Fi starts. Unaffected as a digital pin.
GND	Ground	power	L19. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
3V3	3.3 V rail	power	L20. Output of the on-board regulator. Everything on the board runs from it, so budget what the regulator can spare, not what USB can deliver. A steady 3.3 V supply can also power the board through it, but never with USB plugged in at the same time.
3V3	3.3 V rail	power	R1. Output of the on-board regulator. Everything on the board runs from it, so budget what the regulator can spare, not what USB can deliver. A steady 3.3 V supply can also power the board through it, but never with USB plugged in at the same time.
5V	5 V rail	power	R2. The USB rail, upstream of the regulator. Feed the board here if you are not using USB, or take 5 V out if you are.
GND	Ground	power	R3. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GND	Ground	power	R4. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GPIO1	GPIO1	gpio, adc1, touch	R5
GPIO2	GPIO2	gpio, adc1, touch	R6
GPIO42	GPIO42	gpio, jtag	R7
GPIO41	GPIO41	gpio, jtag	R8
GPIO40	GPIO40	gpio, jtag	R9
GPIO39	GPIO39	gpio, jtag	R10
GPIO38	GPIO38	gpio	R11
GPIO48	GPIO48	gpio	WS2812B RGB LED, single-wire at 800 kHz. The silkscreen says RGB@IO48.
GPIO47	GPIO47	gpio	R13
GPIO21	GPIO21	gpio	R14
GPIO20	GPIO20	gpio, adc2, usb	Native USB-C, D+ . Wired straight to the USB-Serial-JTAG peripheral, no bridge chip in the path.
GPIO19	GPIO19	gpio, adc2, usb	Native USB-C, D− . Wired straight to the USB-Serial-JTAG peripheral, no bridge chip in the path.
GND	Ground	power	R17. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
GND	Ground	power	R18. Ground. Several holes so a breadboard build has one nearby wherever it needs it.
5V	5 V rail	power	R19. The USB rail, upstream of the regulator. Feed the board here if you are not using USB, or take 5 V out if you are.
3V3	3.3 V rail	power	R20. Output of the on-board regulator. Everything on the board runs from it, so budget what the regulator can spare, not what USB can deliver. A steady 3.3 V supply can also power the board through it, but never with USB plugged in at the same time.

For this board

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CAN Bus — An SN65HVD230 CAN transceiver on a TinkerBlock board, for 3.3 V microcontrollers with a CAN controller of their own, such as every ESP32. CTX and CRX go straight across, the 120 Ω fitted on every board belongs only on the two end boards, GND runs with a twisted pair, and one board alone can never finish a message.
I2S Amplifier — An NS4168 I2S amplifier on a TinkerBlock board: the ESP32-S3 sends sound as numbers on three wires and the chip drives a 4 Ω speaker, about 1 W on 3.3 V. CTRL must be driven HIGH or it stays off, the L/R jumper picks which channel the mono chip plays, and neither speaker wire is ground.

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