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366 changes: 366 additions & 0 deletions docs/tutorials/esp32-module-schematic.mdx
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---
title: ESP32 Module Circuit Example
description: >-
Build a schematic-only ESP32-WROOM style module circuit with USB-UART,
enable/reset, boot strapping, crystal, decoupling, and expansion headers.
---

import CircuitPreview from "@site/src/components/CircuitPreview"

## Overview

This tutorial walks through a schematic-only ESP32 module circuit similar to
what you would see in a hardware academy reference design. The goal is not a
finished PCB layout. The goal is a readable schematic that shows the supporting
parts an ESP32-WROOM style module needs before you start routing:

- 3.3 V power input and local decoupling
- EN reset pull-up and reset button
- BOOT strap button on GPIO0
- USB-UART TX/RX wiring
- 40 MHz crystal load capacitors for bare-module variants
- GPIO expansion header labels for the signals you will use later

The examples use only built-in tscircuit primitives so you can paste each block
into a new project without installing a package.

## Final schematic

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board routingDisabled>
<chip
name="U1"
manufacturerPartNumber="ESP32-WROOM-32E"
footprint="module_esp32_wroom_32"
pinLabels={{
pin1: "V3_3",
pin2: "EN",
pin3: "GPIO36",
pin4: "GPIO39",
pin5: "GPIO34",
pin6: "GPIO35",
pin7: "GPIO32",
pin8: "GPIO33",
pin9: "GPIO25",
pin10: "GPIO26",
pin11: "GPIO27",
pin12: "GPIO14",
pin13: "GPIO12",
pin14: "GND",
pin15: "GPIO13",
pin16: "GPIO9",
pin17: "GPIO10",
pin18: "GPIO11",
pin19: "GPIO6",
pin20: "GPIO7",
pin21: "GPIO8",
pin22: "GPIO15",
pin23: "GPIO2",
pin24: "GPIO0",
pin25: "GPIO4",
pin26: "GPIO16",
pin27: "GPIO17",
pin28: "GPIO5",
pin29: "GPIO18",
pin30: "GPIO19",
pin31: "GND2",
pin32: "GPIO21",
pin33: "RXD0",
pin34: "TXD0",
pin35: "GPIO22",
pin36: "GPIO23",
pin37: "GND3",
pin38: "ANT"
}}
schPinArrangement={{
leftSide: {
direction: "top-to-bottom",
pins: [
"V3_3",
"EN",
"GPIO36",
"GPIO39",
"GPIO34",
"GPIO35",
"GPIO32",
"GPIO33",
"GPIO25",
"GPIO26",
"GPIO27",
"GPIO14",
"GPIO12"
],
},
rightSide: {
direction: "top-to-bottom",
pins: [
"TXD0",
"RXD0",
"GPIO23",
"GPIO22",
"GPIO21",
"GPIO19",
"GPIO18",
"GPIO17",
"GPIO16",
"GPIO5",
"GPIO4",
"GPIO0",
"GPIO2",
"GPIO15",
"GND"
],
},
}}
/>

<pinheader
name="J1"
pinCount={6}
pinLabels={["GND", "V3_3", "TXD0", "RXD0", "EN", "GPIO0"]}
/>
<pinheader
name="J2"
pinCount={8}
pinLabels={["GPIO23", "GPIO22", "GPIO21", "GPIO19", "GPIO18", "GPIO17", "GPIO16", "GPIO5"]}
/>

<chip
name="U2"
manufacturerPartNumber="USB-UART Bridge"
footprint="qfn16"
pinLabels={{
pin1: "VCC",
pin2: "GND",
pin3: "TXD",
pin4: "RXD",
pin5: "DTR",
pin6: "RTS",
}}
schPinArrangement={{
leftSide: { direction: "top-to-bottom", pins: ["VCC", "GND"] },
rightSide: { direction: "top-to-bottom", pins: ["TXD", "RXD", "DTR", "RTS"] },
}}
/>

<resistor name="R1" resistance="10k" footprint="0402" />
<resistor name="R2" resistance="10k" footprint="0402" />
<capacitor name="C1" capacitance="10uF" footprint="0603" />
<capacitor name="C2" capacitance="100nF" footprint="0402" />
<capacitor name="C3" capacitance="100nF" footprint="0402" />
<pushbutton name="SW1" />
<pushbutton name="SW2" />
<crystal name="Y1" frequency="40MHz" footprint="crystal_4pin" />
<capacitor name="C4" capacitance="18pF" footprint="0402" />
<capacitor name="C5" capacitance="18pF" footprint="0402" />

<trace from=".J1 .V3_3" to=".U1 .V3_3" />
<trace from=".J1 .GND" to=".U1 .GND" />
<trace from=".J1 .V3_3" to=".C1 > .pin1" />
<trace from=".J1 .V3_3" to=".C2 > .pin1" />
<trace from=".J1 .V3_3" to=".C3 > .pin1" />
<trace from=".C1 > .pin2" to=".J1 .GND" />
<trace from=".C2 > .pin2" to=".J1 .GND" />
<trace from=".C3 > .pin2" to=".J1 .GND" />

<trace from=".J1 .V3_3" to=".R1 > .pin1" />
<trace from=".R1 > .pin2" to=".U1 .EN" />
<trace from=".U1 .EN" to=".SW1 > .pin1" />
<trace from=".SW1 > .pin2" to=".J1 .GND" />

<trace from=".J1 .V3_3" to=".R2 > .pin1" />
<trace from=".R2 > .pin2" to=".U1 .GPIO0" />
<trace from=".U1 .GPIO0" to=".SW2 > .pin1" />
<trace from=".SW2 > .pin2" to=".J1 .GND" />

<trace from=".U2 .TXD" to=".U1 .RXD0" />
<trace from=".U2 .RXD" to=".U1 .TXD0" />
<trace from=".U2 .VCC" to=".J1 .V3_3" />
<trace from=".U2 .GND" to=".J1 .GND" />

<trace from=".Y1 > .pin1" to=".U1 .GPIO32" />
<trace from=".Y1 > .pin3" to=".U1 .GPIO33" />
<trace from=".Y1 > .pin1" to=".C4 > .pin1" />
<trace from=".Y1 > .pin3" to=".C5 > .pin1" />
<trace from=".C4 > .pin2" to=".J1 .GND" />
<trace from=".C5 > .pin2" to=".J1 .GND" />

<trace from=".J2 .GPIO23" to=".U1 .GPIO23" />
<trace from=".J2 .GPIO22" to=".U1 .GPIO22" />
<trace from=".J2 .GPIO21" to=".U1 .GPIO21" />
<trace from=".J2 .GPIO19" to=".U1 .GPIO19" />
<trace from=".J2 .GPIO18" to=".U1 .GPIO18" />
<trace from=".J2 .GPIO17" to=".U1 .GPIO17" />
<trace from=".J2 .GPIO16" to=".U1 .GPIO16" />
<trace from=".J2 .GPIO5" to=".U1 .GPIO5" />
</board>
)
`} />

## Step 1: Represent the ESP32 module

Start with the module symbol. The pin labels matter more than the placeholder
footprint for this schematic-only exercise because the labels become stable
selectors for traces and documentation.

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board routingDisabled>
<chip
name="U1"
manufacturerPartNumber="ESP32-WROOM-32E"
footprint="module_esp32_wroom_32"
pinLabels={{
pin1: "V3_3",
pin2: "EN",
pin24: "GPIO0",
pin29: "GPIO18",
pin30: "GPIO19",
pin32: "GPIO21",
pin33: "RXD0",
pin34: "TXD0",
pin35: "GPIO22",
pin36: "GPIO23",
pin37: "GND"
}}
schPinArrangement={{
leftSide: { direction: "top-to-bottom", pins: ["V3_3", "EN", "GPIO0"] },
rightSide: { direction: "top-to-bottom", pins: ["TXD0", "RXD0", "GPIO23", "GPIO22", "GPIO21", "GPIO19", "GPIO18", "GND"] },
}}
/>
</board>
)
`} />

## Step 2: Add power and decoupling

ESP32 modules draw short Wi-Fi current bursts, so place bulk and high-frequency
decoupling on the 3.3 V rail. In a real layout, these capacitors should be close
to the module power pins and should return to the same ground reference.

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board routingDisabled>
<chip
name="U1"
manufacturerPartNumber="ESP32-WROOM-32E"
footprint="module_esp32_wroom_32"
pinLabels={{ pin1: "V3_3", pin37: "GND" }}
schPinArrangement={{ leftSide: { direction: "top-to-bottom", pins: ["V3_3", "GND"] } }}
/>
<pinheader name="J1" pinCount={2} pinLabels={["V3_3", "GND"]} />
<capacitor name="C1" capacitance="10uF" footprint="0603" />
<capacitor name="C2" capacitance="100nF" footprint="0402" />
<capacitor name="C3" capacitance="100nF" footprint="0402" />

<trace from=".J1 .V3_3" to=".U1 .V3_3" />
<trace from=".J1 .GND" to=".U1 .GND" />
<trace from=".J1 .V3_3" to=".C1 > .pin1" />
<trace from=".J1 .V3_3" to=".C2 > .pin1" />
<trace from=".J1 .V3_3" to=".C3 > .pin1" />
<trace from=".C1 > .pin2" to=".J1 .GND" />
<trace from=".C2 > .pin2" to=".J1 .GND" />
<trace from=".C3 > .pin2" to=".J1 .GND" />
</board>
)
`} />

## Step 3: Add reset and boot strapping

The EN pin needs a pull-up and a reset button to ground. GPIO0 needs a pull-up
and a BOOT button to ground so you can enter the serial bootloader while
flashing firmware.

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board routingDisabled>
<chip
name="U1"
manufacturerPartNumber="ESP32-WROOM-32E"
footprint="module_esp32_wroom_32"
pinLabels={{ pin1: "V3_3", pin2: "EN", pin24: "GPIO0", pin37: "GND" }}
schPinArrangement={{ leftSide: { direction: "top-to-bottom", pins: ["V3_3", "EN", "GPIO0", "GND"] } }}
/>
<resistor name="R1" resistance="10k" footprint="0402" />
<resistor name="R2" resistance="10k" footprint="0402" />
<pushbutton name="SW1" />
<pushbutton name="SW2" />

<trace from=".U1 .V3_3" to=".R1 > .pin1" />
<trace from=".R1 > .pin2" to=".U1 .EN" />
<trace from=".U1 .EN" to=".SW1 > .pin1" />
<trace from=".SW1 > .pin2" to=".U1 .GND" />

<trace from=".U1 .V3_3" to=".R2 > .pin1" />
<trace from=".R2 > .pin2" to=".U1 .GPIO0" />
<trace from=".U1 .GPIO0" to=".SW2 > .pin1" />
<trace from=".SW2 > .pin2" to=".U1 .GND" />
</board>
)
`} />

## Step 4: Wire USB-UART programming

Cross the UART bridge signals: bridge TXD goes to ESP32 RXD0, and bridge RXD
goes to ESP32 TXD0. The optional DTR and RTS outputs can be added later for
auto-reset, but a manual EN and BOOT pair is enough for a clear first schematic.

<CircuitPreview splitView={false} hidePCBTab hide3DTab defaultView="schematic" code={`
export default () => (
<board routingDisabled>
<chip
name="U1"
manufacturerPartNumber="ESP32-WROOM-32E"
footprint="module_esp32_wroom_32"
pinLabels={{ pin33: "RXD0", pin34: "TXD0", pin37: "GND", pin1: "V3_3" }}
schPinArrangement={{ rightSide: { direction: "top-to-bottom", pins: ["TXD0", "RXD0", "V3_3", "GND"] } }}
/>
<chip
name="U2"
manufacturerPartNumber="USB-UART Bridge"
footprint="qfn16"
pinLabels={{ pin1: "VCC", pin2: "GND", pin3: "TXD", pin4: "RXD" }}
schPinArrangement={{
leftSide: { direction: "top-to-bottom", pins: ["VCC", "GND"] },
rightSide: { direction: "top-to-bottom", pins: ["TXD", "RXD"] },
}}
/>

<trace from=".U2 .TXD" to=".U1 .RXD0" />
<trace from=".U2 .RXD" to=".U1 .TXD0" />
<trace from=".U2 .VCC" to=".U1 .V3_3" />
<trace from=".U2 .GND" to=".U1 .GND" />
</board>
)
`} />

## Step 5: Add expansion headers

Break out the signals you actually plan to use. The header below keeps the
common SPI-capable pins together, then leaves the UART and reset pins on the
programming header.

| Header pin | ESP32 signal | Typical use |
| ---------- | ------------ | ----------- |
| GPIO23 | MOSI | SPI data out |
| GPIO22 | SCL | I2C clock |
| GPIO21 | SDA | I2C data |
| GPIO19 | MISO | SPI data in |
| GPIO18 | SCK | SPI clock |
| GPIO17 | TX2 | Secondary UART |
| GPIO16 | RX2 | Secondary UART |
| GPIO5 | CS | SPI chip select |

## Schematic review checklist

Before turning this into a PCB, check the schematic against this list:

- Every 3.3 V pin has a nearby 100 nF decoupling capacitor.
- EN is pulled up and can be pulled low by the reset button.
- GPIO0 is pulled up and can be pulled low by the BOOT button.
- USB-UART TXD/RXD are crossed into ESP32 RXD0/TXD0.
- GPIO12, GPIO0, GPIO2, GPIO15, and EN are not accidentally forced into a bad
boot strap state by external circuitry.
- The antenna side of the module is kept free of copper and tall components
when you move from schematic to PCB.
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