Building an ESP32 Module Circuit

Overview

This tutorial will walk you through building an ESP32-WROOM-32 minimal system circuit using tscircuit. We'll cover the power supply with an LDO voltage regulator, decoupling capacitors, reset and boot mode circuits, and a status LED — everything needed to get an ESP32 module up and running.

The ESP32 is a popular low-cost microcontroller with integrated Wi-Fi and Bluetooth, making it ideal for IoT projects. A minimal system circuit ensures the ESP32 can boot reliably and communicate over serial.

ESP32 Minimum System Requirements

An ESP32 minimum system needs the following to boot reliably:

• Power Supply — The ESP32 requires a stable 3.3V supply. We use a USB-C connector with an AMS1117-3.3 LDO to step down 5V from USB to 3.3V.
• Decoupling Capacitors — 10uF bulk capacitors on the LDO input and output, plus a 0.1uF ceramic capacitor close to the ESP32 for high-frequency noise filtering.
• Reset Circuit — The EN (CHIP_PU) pin must be pulled high via a 10k resistor. A push button pulls it low to reset the chip.
• Boot Mode Selection — The GPIO0 pin determines the boot mode. Pulled high for normal boot (flash mode), pulled low for download mode.
• Status LED — A blue LED on GPIO2 provides visual feedback (GPIO2 also serves as a debug output during boot).

Building the Circuit Step by Step

Step 1: ESP32-WROOM-32 Module

The ESP32-WROOM-32 is a module that integrates the ESP32 chip, Flash memory, and antenna into a single package. We define it using the <chip> component with pin labels matching the module's pinout.

The ESP32-WROOM-32 has 38 pins total. For our schematic, we include the essential pins: power (3V3, VDD, GND), control (EN, IO0), communication (TX, RX), and several GPIO pins.

Step 2: Power Supply (USB-C + LDO)

The ESP32 operates at 3.3V, but USB provides 5V. We use an AMS1117-3.3 LDO (Low Dropout Regulator) to step down the voltage. The SmdUsbC component provides the USB-C connector, and we add 10uF capacitors on both the input and output of the LDO for stability.

Step 3: Connect Power to ESP32

Now we connect the 3.3V output from the LDO to the ESP32's power pins. The ESP32-WROOM-32 has two 3.3V pins (3V3 and VDD) and two GND pins. We also add a 0.1uF decoupling capacitor close to the ESP32's power pins to filter high-frequency noise.

Step 4: Reset and Boot Mode Circuits

The ESP32 has two critical control pins:

• EN (CHIP_PU) — The enable/reset pin. Must be pulled high (3.3V) for normal operation. Pulling it low resets the chip. We use a 10k pull-up resistor and a push button to ground.
• IO0 — Determines the boot mode. Pulled high = normal boot from flash, pulled low = serial download mode. We use a 10k pull-up resistor for normal operation.

Step 5: Status LED

We add a blue LED on GPIO2 with a 1k current-limiting resistor. GPIO2 is useful for a status LED because it also outputs a debug signal during boot — the LED will pulse briefly when the ESP32 starts up, providing visual confirmation that the board is working.

Step 6: Complete Circuit

Now we combine all the sub-circuits into the complete ESP32 minimum system. This includes the USB-C power supply, LDO regulator, ESP32 module, decoupling capacitors, reset circuit, boot mode selection, and status LED.

import { SmdUsbC } from "@tsci/seveibar.smd-usb-c"

export default () => {
return (
  <board width="60mm" height="80mm" routingDisabled>
    {/* USB-C Connector */}
    <SmdUsbC
      name="J1"
      connections={{
        GND1: "net.GND",
        GND2: "net.GND",
        VBUS1: "net.VBUS",
        VBUS2: "net.VBUS",
      }}
      schX={-8}
      schY={3}
    />

    {/* LDO Voltage Regulator - AMS1117-3.3 */}
    <chip
      name="U2"
      manufacturerPartNumber="AMS1117-3.3"
      schWidth={2}
      schHeight={3}
      schPortArrangement={{
        leftSide: {
          direction: "top-to-bottom",
          pins: ["GND", "VO"]
        },
        rightSide: {
          direction: "top-to-bottom",
          pins: ["VI"]
        }
      }}
      pinLabels={{
        pin1: ["pin1", "GND"],
        pin2: ["pin2", "VO"],
        pin3: ["pin3", "VI"]
      }}
      supplierPartNumbers={{ jlcpcb: ["C6186"] }}
      schX={-3}
      schY={3}
    />

    {/* ESP32-WROOM-32 Module */}
    <chip
      name="U1"
      manufacturerPartNumber="ESP32-WROOM-32"
      schWidth={5}
      schHeight={8}
      schPortArrangement={{
        leftSide: {
          direction: "top-to-bottom",
          pins: ["GND", "3V3", "EN", "IO0", "IO2", "IO4", "IO5", "IO12", "IO13", "IO14", "IO15", "IO16", "IO17", "IO25", "IO26"]
        },
        rightSide: {
          direction: "top-to-bottom",
          pins: ["GND1", "VDD", "IO34", "IO35", "IO32", "IO33", "IO27", "IO23", "IO22", "IO21", "IO19", "TX", "RX"]
        }
      }}
      pinLabels={{
        pin1: ["pin1", "GND"],
        pin2: ["pin2", "3V3"],
        pin3: ["pin3", "EN"],
        pin4: ["pin4", "IO0"],
        pin5: ["pin5", "IO2"],
        pin6: ["pin6", "IO4"],
        pin7: ["pin7", "IO5"],
        pin8: ["pin8", "IO12"],
        pin9: ["pin9", "IO13"],
        pin10: ["pin10", "IO14"],
        pin11: ["pin11", "IO15"],
        pin12: ["pin12", "IO16"],
        pin13: ["pin13", "IO17"],
        pin14: ["pin14", "IO25"],
        pin15: ["pin15", "IO26"],
        pin16: ["pin16", "GND1"],
        pin17: ["pin17", "VDD"],
        pin18: ["pin18", "IO34"],
        pin19: ["pin19", "IO35"],
        pin20: ["pin20", "IO32"],
        pin21: ["pin21", "IO33"],
        pin22: ["pin22", "IO27"],
        pin23: ["pin23", "IO23"],
        pin24: ["pin24", "IO22"],
        pin25: ["pin25", "IO21"],
        pin26: ["pin26", "IO19"],
        pin27: ["pin27", "TX"],
        pin28: ["pin28", "RX"]
      }}
      supplierPartNumbers={{ jlcpcb: ["C829502"] }}
      schX={5}
      schY={0}
    />

    {/* Input Capacitor for LDO - 10uF */}
    <capacitor
      name="C1"
      capacitance="10uF"
      footprint="0805"
      supplierPartNumbers={{ jlcpcb: ["C15850"] }}
      schX={-5}
      schY={0}
    />

    {/* Output Capacitor for LDO - 10uF */}
    <capacitor
      name="C2"
      capacitance="10uF"
      footprint="0805"
      supplierPartNumbers={{ jlcpcb: ["C15850"] }}
      schX={-1}
      schY={0}
    />

    {/* Decoupling Capacitor near ESP32 - 0.1uF */}
    <capacitor
      name="C3"
      capacitance="0.1uF"
      footprint="0402"
      supplierPartNumbers={{ jlcpcb: ["C307514"] }}
      schX={2}
      schY={-5}
    />

    {/* Pull-up Resistor for EN - 10k */}
    <resistor
      name="R1"
      resistance="10k"
      footprint="0402"
      supplierPartNumbers={{ jlcpcb: ["C25744"] }}
      schX={0}
      schY={-2}
    />

    {/* Pull-up Resistor for IO0 - 10k */}
    <resistor
      name="R2"
      resistance="10k"
      footprint="0402"
      supplierPartNumbers={{ jlcpcb: ["C25744"] }}
      schX={0}
      schY={-4}
    />

    {/* Reset Button */}
    <pushbutton
      name="SW1"
      footprint="pushbutton"
      schX={-2}
      schY={-2}
    />

    {/* Status LED */}
    <led
      name="LED1"
      color="blue"
      footprint="0603"
      supplierPartNumbers={{ jlcpcb: ["C72041"] }}
      schX={9}
      schY={-4}
    />

    {/* LED Current Limiting Resistor - 1k */}
    <resistor
      name="R3"
      resistance="1k"
      footprint="0402"
      supplierPartNumbers={{ jlcpcb: ["C11702"] }}
      schX={9}
      schY={-2}
    />

    {/* Power Traces */}
    <trace from=".U2 .VI" to="net.VBUS" />
    <trace from=".U2 .VO" to="net.V3_3" />
    <trace from=".U2 .GND" to="net.GND" />

    {/* Input Cap for LDO */}
    <trace from=".C1 .pos" to="net.VBUS" />
    <trace from=".C1 .neg" to="net.GND" />

    {/* Output Cap for LDO */}
    <trace from=".C2 .pos" to="net.V3_3" />
    <trace from=".C2 .neg" to="net.GND" />

    {/* ESP32 Power */}
    <trace from=".U1 .3V3" to="net.V3_3" />
    <trace from=".U1 .VDD" to="net.V3_3" />
    <trace from=".U1 .GND" to="net.GND" />
    <trace from=".U1 .GND1" to="net.GND" />

    {/* Decoupling Cap */}
    <trace from=".C3 .pos" to="net.V3_3" />
    <trace from=".C3 .neg" to="net.GND" />

    {/* EN Pull-up */}
    <trace from=".R1 .pos" to="net.V3_3" />
    <trace from=".R1 .neg" to=".U1 .EN" />

    {/* Reset Button */}
    <trace from=".SW1 .pin1" to=".U1 .EN" />
    <trace from=".SW1 .pin2" to="net.GND" />

    {/* IO0 Pull-up */}
    <trace from=".R2 .pos" to="net.V3_3" />
    <trace from=".R2 .neg" to=".U1 .IO0" />

    {/* Status LED */}
    <trace from=".R3 .pos" to="net.V3_3" />
    <trace from=".R3 .neg" to=".LED1 .pos" />
    <trace from=".LED1 .neg" to=".U1 .IO2" />
  </board>
)
}

Component Reference

Component	Designator	JLCPCB Part #	Description
ESP32-WROOM-32	U1	C829502	Wi-Fi + Bluetooth MCU module
AMS1117-3.3	U2	C6186	3.3V LDO voltage regulator
10uF Capacitor	C1, C2	C15850	LDO input/output bulk capacitor (0805)
0.1uF Capacitor	C3	C307514	ESP32 decoupling capacitor (0402)
10k Resistor	R1, R2	C25744	EN and IO0 pull-up resistors (0402)
1k Resistor	R3	C11702	LED current-limiting resistor (0402)
Blue LED	LED1	C72041	Status indicator LED (0603)
Push Button	SW1	—	Reset button
USB-C Connector	J1	—	Power input (via SmdUsbC)

Boot Mode Summary

The ESP32 boot mode is determined by the state of specific pins at startup:

IO0	IO2	IO12	EN	Boot Mode
H	-	-	↑	SPI Flash Boot (normal)
L	-	-	↑	Download Boot (UART)
-	-	H	↑	SPI Flash Boot
-	-	L	↑	SDIO Boot (rarely used)

In our circuit, IO0 is pulled high by R2 (10k), so the ESP32 will boot from SPI Flash by default. To enter download mode, you would hold the BOOT button (not shown — connect IO0 to GND) while pressing and releasing the RESET button.

Next Steps

• Add a USB-to-UART bridge — Add a CP2102 or CH340 chip to enable programming via USB without an external programmer
• Add a BOOT button — Add a second push button on IO0 to easily enter download mode
• Expand GPIO connections — Add pin headers to expose all GPIO pins for prototyping
• Add battery charging — Integrate a LiPo battery charger like the TP4056 for portable projects
• Order the PCB — Follow the Ordering Prototypes guide to manufacture your board