# ESP32-S2-SOLO-U-N4

**Espressif Systems** · RF and Wireless · 40-SMD Module

ESP32-S2-SOLO-U-N4 from Espressif Systems, in a 40-SMD Module. Pinout and pin descriptions extracted from the manufacturer datasheet (extract_pins, cross-checked by a second model); symbol, footprint, and 3D from KiCad-official CAD.

## Pinout

| Pin | Name | Type | Function |
|---|---|---|---|
| 1 | GND | power_in | Ground. |
| 2 | 3V3 | power_in | Power supply input; the recommended VDD33 range is 3.0 V to 3.6 V with 3.3 V typical. |
| 3 | EN | input | Chip enable: high turns the chip on and low powers it off; the pin must not be left floating. |
| 4 | IO4 | bidirectional | Multifunction I/O: RTC_GPIO4, GPIO4, TOUCH4, ADC1_CH3. |
| 5 | IO5 | bidirectional | Multifunction I/O: RTC_GPIO5, GPIO5, TOUCH5, ADC1_CH4. |
| 6 | IO6 | bidirectional | Multifunction I/O: RTC_GPIO6, GPIO6, TOUCH6, ADC1_CH5. |
| 7 | IO7 | bidirectional | Multifunction I/O: RTC_GPIO7, GPIO7, TOUCH7, ADC1_CH6. |
| 8 | IO15 | bidirectional | Multifunction I/O: RTC_GPIO15, GPIO15, U0RTS, ADC2_CH4, XTAL_32K_P. |
| 9 | IO16 | bidirectional | Multifunction I/O: RTC_GPIO16, GPIO16, U0CTS, ADC2_CH5, XTAL_32K_N. |
| 10 | IO17 | bidirectional | Multifunction I/O: RTC_GPIO17, GPIO17, U1TXD, ADC2_CH6, DAC_1. |
| 11 | IO18 | bidirectional | Multifunction I/O: RTC_GPIO18, GPIO18, U1RXD, ADC2_CH7, DAC_2, CLK_OUT3. |
| 12 | IO8 | bidirectional | Multifunction I/O: RTC_GPIO8, GPIO8, TOUCH8, ADC1_CH7. |
| 13 | IO19 | bidirectional | Multifunction I/O: RTC_GPIO19, GPIO19, U1RTS, ADC2_CH8, CLK_OUT2, USB_D-. |
| 14 | IO20 | bidirectional | Multifunction I/O: RTC_GPIO20, GPIO20, U1CTS, ADC2_CH9, CLK_OUT1, USB_D+. |
| 15 | IO3 | bidirectional | Multifunction I/O: RTC_GPIO3, GPIO3, TOUCH3, ADC1_CH2. |
| 16 | IO46 | input | Input-only GPIO46; also a strapping pin that selects the chip boot mode and ROM message printing at reset. |
| 17 | IO9 | bidirectional | Multifunction I/O: RTC_GPIO9, GPIO9, TOUCH9, ADC1_CH8, FSPIHD. |
| 18 | IO10 | bidirectional | Multifunction I/O: RTC_GPIO10, GPIO10, TOUCH10, ADC1_CH9, FSPICS0, FSPIIO4. |
| 19 | IO11 | bidirectional | Multifunction I/O: RTC_GPIO11, GPIO11, TOUCH11, ADC2_CH0, FSPID, FSPIIO5. |
| 20 | IO12 | bidirectional | Multifunction I/O: RTC_GPIO12, GPIO12, TOUCH12, ADC2_CH1, FSPICLK, FSPIIO6. |
| 21 | IO13 | bidirectional | Multifunction I/O: RTC_GPIO13, GPIO13, TOUCH13, ADC2_CH2, FSPIQ, FSPIIO7. |
| 22 | IO14 | bidirectional | Multifunction I/O: RTC_GPIO14, GPIO14, TOUCH14, ADC2_CH3, FSPIWP, FSPIDQS. |
| 23 | IO21 | bidirectional | Multifunction I/O: RTC_GPIO21, GPIO21. |
| 24 | IO33 | bidirectional | Multifunction I/O: SPIIO4, GPIO33, FSPIHD. |
| 25 | IO34 | bidirectional | Multifunction I/O: SPIIO5, GPIO34, FSPICS0. |
| 26 | IO45 | bidirectional | GPIO45; also a strapping pin that selects the VDD_SPI voltage source at reset. |
| 27 | IO0 | bidirectional | RTC_GPIO0, GPIO0; strapping pin for chip boot mode with a default internal pull-up. |
| 28 | IO35 | bidirectional | Multifunction I/O: SPIIO6, GPIO35, FSPID. |
| 29 | IO36 | bidirectional | Multifunction I/O: SPIIO7, GPIO36, FSPICLK. |
| 30 | IO37 | bidirectional | Multifunction I/O: SPIDQS, GPIO37, FSPIQ. |
| 31 | IO38 | bidirectional | Multifunction I/O: GPIO38, FSPIWP. |
| 32 | IO39 | bidirectional | Multifunction I/O: MTCK, GPIO39, CLK_OUT3. |
| 33 | IO40 | bidirectional | Multifunction I/O: MTDO, GPIO40, CLK_OUT2. |
| 34 | IO41 | bidirectional | Multifunction I/O: MTDI, GPIO41, CLK_OUT1. |
| 35 | IO42 | bidirectional | Multifunction I/O: MTMS, GPIO42. |
| 36 | RXD0 | bidirectional | UART0 receive (U0RXD), also GPIO44 and CLK_OUT2. |
| 37 | TXD0 | bidirectional | UART0 transmit (U0TXD), also GPIO43 and CLK_OUT1; the default output for ROM boot messages. |
| 38 | IO2 | bidirectional | Multifunction I/O: RTC_GPIO2, GPIO2, TOUCH2, ADC1_CH1. |
| 39 | IO1 | bidirectional | Multifunction I/O: RTC_GPIO1, GPIO1, TOUCH1, ADC1_CH0. |
| 40 | GND | power_in | Ground. |
| 41 | EPAD | power_in | Ground exposed pad; soldering it to the base board ground is optional but optimizes thermal performance. |

## Key specifications

| Parameter | Value |
|---|---|
| Manufacturer | Espressif Systems |
| Package | 40-SMD Module |
| Category | RF and Wireless |
| Pins | 41 |

## Electrical characteristics

Limits as printed in the datasheet (page.json `metadata.characteristics` carries them as data).

| Parameter | Symbol | Min | Typ | Max | Unit | Conditions | Page |
|---|---|---|---|---|---|---|---|
| Power supply voltage | VDD33 | -0.3 |  | 3.6 | V |  | 15 |
| Storage temperature | TSTORE | -40 |  | 105 | °C |  | 15 |
| Power supply voltage | VDD33 | 3 | 3.3 | 3.6 | V |  | 15 |
| Current delivered by external power supply | IVDD | 0.5 |  |  | A |  | 15 |
| Operating ambient temperature | TA | -40 |  | 85 | °C | 85 °C version | 15 |
| Low-level input voltage | VIL | -0.3 |  |  | V |  | 15 |
| Chip reset voltage | VIL_nRST | -0.3 |  |  | V |  | 15 |
| High-level input current | IIH |  |  | 50 | nA |  | 15 |
| Low-level input current | IIL |  |  | 50 | nA |  | 15 |
| TX EVM limit |  |  |  | -10 | dB | 802.11b, 1 Mbps, DSSS | 18 |
| TX EVM limit |  |  |  | -5 | dB | 802.11g, 6 Mbps, OFDM | 18 |
| TX EVM limit |  |  |  | -25 | dB | 802.11g, 54 Mbps, OFDM | 18 |
| TX EVM limit |  |  |  | -27 | dB | 802.11n, HT20, MCS7 | 18 |

## Materials and finish

As the datasheet states them (page.json `metadata.appearance`; the 3D model's colours follow it).

| Part | Material | Colour / plating | Datasheet says | Page |
|---|---|---|---|---|
| contacts |  | tin | Solder, Sn-Ag-Cu (SAC305) lead-free solder alloy Figure 13: Reflow Profile | 28 |

## CAD (KiCad official)

- Symbol: `ESP32-S2-SOLO-U-N4`
- Footprint: `PCM_Espressif:ESP32-S2-SOLO`
- 3D model: 40-SMD Module (KiCad packages3D, STEP)
- 3D model files: `esp32-s2-solo-u-n4-etched.step` / `esp32-s2-solo-u-n4-etched.glb` carry the MPN laser-etched on the die in a toggleable `Adom.LaserEtch` group (Fusion-ready); `esp32-s2-solo-u-n4.step` / `esp32-s2-solo-u-n4.glb` are the bare package body.

## Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

- **Datasheet:** [Espressif Systems datasheet](https://www.espressif.com/sites/default/files/documentation/esp32-s2-solo_esp32-s2-solo-u_datasheet_en.pdf) (34 pp, sha256 `dbfee97a9809455c`, retrieved 2026-10-28, tier: manufacturer)
- **Extractor:** parts-factory `2.0.0` / `extract_pins 0.3`, primary `claude-haiku-5-5` (text), consensus `claude-sonnet-5-5` (agreed), guards: pin_guards 0.1: passed. Pins are checked against the footprint pad set and their cited datasheet pages before publish.
- **CAD:** KiCad official libraries (CC-BY-SA 4.0).

[Datasheet PDF](docs/esp32-s2-solo-u-n4-datasheet.pdf)