Replacing the EOL 43-pin ESP32-S2-WROOM, Espressif's ESP32-S2-SOLO-2 (18.0×25.5 mm PCB antenna) and ESP32-S2-SOLO-2U (18.0×19.2 mm U.FL) adopt the modern 40+1 pad 1.27 mm castellated footprint shared with ESP32-S3-WROOM-1. Thirty-six GPIOs (35 bidirectional + input-only IO46) expose native USB OTG (IO19/IO20), 20× ADC channels, 2× 8-bit DACs (IO17/IO18), and 14× touch sensors.
-N4/-N8/-N16 include Quad SPI flash; -N4R2 uses ESP32-S2FN4R2 with 4 MB flash + 2 MB PSRAM.
Add the peripherals you need and plan the pin assignments
| Pin # | Label | Type | Functions | Warnings & Notes |
|---|---|---|---|---|
| 1 | GND | ground | GND |
Module system ground (0V)
|
| 2 | 3V3 | power | 3V3 |
[CAUTION] 3.0V–3.6V supply only (>=500 mA current capability + 10 µF & 0.1 µF decoupling)
Wi-Fi TX bursts draw high peak current. Exceeding 3.6V permanently damages the SoC and onboard flash.
Main 3.3V module power supply input (3.0V–3.6V; >=500 mA regulator recommended)
|
| 3 | EN CHIP_PU | reset | CHIP_PU |
[CAUTION] Active-HIGH chip enable / reset — never leave floating
Add an external 10 kΩ pull-up to 3.3V and 1 µF capacitor to GND.
Active-HIGH chip enable / reset input (EN / CHIP_PU)
|
| 4 | IO4 GPIO4 | mixed | GPIO4 ADC1_CH3 TOUCH4 |
General-purpose 3.3V GPIO4 (NOT 5V tolerant)
|
| 5 | IO5 GPIO5 | mixed | GPIO5 ADC1_CH4 TOUCH5 |
General-purpose 3.3V GPIO5 (NOT 5V tolerant)
|
| 6 | IO6 GPIO6 | mixed | GPIO6 ADC1_CH5 TOUCH6 |
General-purpose 3.3V GPIO6 (NOT 5V tolerant)
|
| 7 | IO7 GPIO7 | mixed | GPIO7 ADC1_CH6 TOUCH7 |
General-purpose 3.3V GPIO7 (NOT 5V tolerant)
|
| 8 | IO15 GPIO15 | mixed | GPIO15 ADC2_CH4 XTAL_32K_P |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO15 (NOT 5V tolerant)
|
| 9 | IO16 GPIO16 | mixed | GPIO16 ADC2_CH5 XTAL_32K_N |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO16 (NOT 5V tolerant)
|
| 10 | IO17 GPIO17 | mixed | GPIO17 ADC2_CH6 DAC_1 U1TXD |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO17 (NOT 5V tolerant)
|
| 11 | IO18 GPIO18 | mixed | GPIO18 ADC2_CH7 DAC_2 U1RXD |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO18 (NOT 5V tolerant)
|
| 12 | IO8 GPIO8 | mixed | GPIO8 ADC1_CH7 TOUCH8 |
General-purpose 3.3V GPIO8 (NOT 5V tolerant)
|
| 13 | IO19 GPIO19 | mixed | GPIO19 ADC2_CH8 USB_D- |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
[INFO] Native Full-Speed USB OTG 1.1 differential pair (D- / D+)
Reconfiguring GPIO19/GPIO20 as digital I/O disconnects native USB CDC/DFU.
General-purpose 3.3V GPIO19 (NOT 5V tolerant)
|
| 14 | IO20 GPIO20 | mixed | GPIO20 ADC2_CH9 USB_D+ |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
[INFO] Native Full-Speed USB OTG 1.1 differential pair (D- / D+)
Reconfiguring GPIO19/GPIO20 as digital I/O disconnects native USB CDC/DFU.
General-purpose 3.3V GPIO20 (NOT 5V tolerant)
|
| 15 | IO3 GPIO3 | mixed | GPIO3 ADC1_CH2 TOUCH3 |
General-purpose 3.3V GPIO3 (NOT 5V tolerant)
|
| 16 | IO46 GPIO46 | digital | GPIO46 |
[CAUTION] Input-only strapping pin (fixed internal pull-down; NO output driver!)
On ESP32-S2, GPIO46 has no output buffer and cannot drive signals high or low. Also sampled at reset for boot mode & ROM log printing (keep LOW at reset).
Input-only strapping pin GPIO46 (no output driver, internal pull-down)
|
| 17 | IO9 GPIO9 | mixed | GPIO9 ADC1_CH8 TOUCH9 |
General-purpose 3.3V GPIO9 (NOT 5V tolerant)
|
| 18 | IO10 GPIO10 | mixed | GPIO10 ADC1_CH9 TOUCH10 FSPICS0 |
General-purpose 3.3V GPIO10 (NOT 5V tolerant)
|
| 19 | IO11 GPIO11 | mixed | GPIO11 ADC2_CH0 TOUCH11 FSPID |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO11 (NOT 5V tolerant)
|
| 20 | IO12 GPIO12 | mixed | GPIO12 ADC2_CH1 TOUCH12 FSPICLK |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO12 (NOT 5V tolerant)
|
| 21 | IO13 GPIO13 | mixed | GPIO13 ADC2_CH2 TOUCH13 FSPIQ |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO13 (NOT 5V tolerant)
|
| 22 | IO14 GPIO14 | mixed | GPIO14 ADC2_CH3 TOUCH14 |
[CAUTION] ADC2 channel restricted during Wi-Fi transmission
Prefer ADC1 (GPIO1–GPIO10) for analog reads when Wi-Fi is active.
General-purpose 3.3V GPIO14 (NOT 5V tolerant)
|
| 23 | IO21 GPIO21 | digital | GPIO21 |
General-purpose 3.3V GPIO21 (NOT 5V tolerant)
|
| 24 | IO33 GPIO33 | digital | GPIO33 |
General-purpose 3.3V GPIO33 (NOT 5V tolerant)
|
| 25 | IO34 GPIO34 | digital | GPIO34 |
General-purpose 3.3V GPIO34 (NOT 5V tolerant)
|
| 26 | IO45 GPIO45 | digital | GPIO45 |
[DANGER] VDD_SPI flash voltage strap (weak pull-down: LOW=3.3V, HIGH=1.8V)
Pulling GPIO45 HIGH at reset switches VDD_SPI to 1.8V, preventing 3.3V flash/PSRAM parts from booting.
General-purpose 3.3V GPIO45 (NOT 5V tolerant)
|
| 27 | IO0 GPIO0 | digital | GPIO0 |
[CAUTION] Boot mode strapping pin (weak pull-up: HIGH=SPI Boot, LOW=Download Boot)
Pulling GPIO0 LOW with GPIO46 LOW at reset enters USB OTG DFU / UART0 Download Boot.
General-purpose 3.3V GPIO0 (NOT 5V tolerant)
|
| 28 | IO35 GPIO35 | digital | GPIO35 |
General-purpose 3.3V GPIO35 (NOT 5V tolerant)
|
| 29 | IO36 GPIO36 | digital | GPIO36 |
General-purpose 3.3V GPIO36 (NOT 5V tolerant)
|
| 30 | IO37 GPIO37 | digital | GPIO37 |
General-purpose 3.3V GPIO37 (NOT 5V tolerant)
|
| 31 | IO38 GPIO38 | digital | GPIO38 |
General-purpose 3.3V GPIO38 (NOT 5V tolerant)
|
| 32 | IO39 GPIO39 | digital | GPIO39 MTCK |
General-purpose 3.3V GPIO39 (NOT 5V tolerant)
|
| 33 | IO40 GPIO40 | digital | GPIO40 MTDO |
General-purpose 3.3V GPIO40 (NOT 5V tolerant)
|
| 34 | IO41 GPIO41 | digital | GPIO41 MTDI |
General-purpose 3.3V GPIO41 (NOT 5V tolerant)
|
| 35 | IO42 GPIO42 | digital | GPIO42 MTMS |
General-purpose 3.3V GPIO42 (NOT 5V tolerant)
|
| 36 | RXD0 GPIO44 | digital | GPIO44 U0RXD |
General-purpose 3.3V GPIO44 (NOT 5V tolerant)
|
| 37 | TXD0 GPIO43 | digital | GPIO43 U0TXD |
General-purpose 3.3V GPIO43 (NOT 5V tolerant)
|
| 38 | IO2 GPIO2 | mixed | GPIO2 ADC1_CH1 TOUCH2 |
General-purpose 3.3V GPIO2 (NOT 5V tolerant)
|
| 39 | IO1 GPIO1 | mixed | GPIO1 ADC1_CH0 TOUCH1 |
General-purpose 3.3V GPIO1 (NOT 5V tolerant)
|
| 40 | GND | ground | GND |
Module system ground (0V)
|
| 41 | EPAD | ground | GND |
Underside exposed thermal & RF ground pad (connect to host GND plane)
|