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ESP32 — Development Guide

Last reviewed: 2026-09-17

The ESP32 is a low-cost, low-power system-on-chip (SoC) microcontroller with integrated Wi-Fi and Bluetooth, developed by Espressif Systems. It's widely used in IoT projects, embedded systems prototyping, and production devices.

Overview

The ESP32 is a dual-core Xtensa LX6 CPU running at up to 240 MHz, with 520 KB of SRAM, integrated 802.11 b/g/n Wi-Fi, Bluetooth 4.2 (BR/EDR + BLE), and a rich set of peripherals (SPI, I²C, I²S, UART, ADC, DAC, PWM, Hall sensor, temperature sensor). It's Arduino-compatible via the Arduino-ESP32 core and also fully supported in PlatformIO and ESP-IDF (Espressif's native SDK).

Topics Covered

Display — ST7789 TFT (240×240)

A key hands-on project: connecting a 1.3" 240×240 IPS TFT display with ST7789 controller to the ESP32 via SPI.

Pin roles:

Signal ESP32 GPIO Function
VCC 3.3V Display logic power
GND GND Ground
BLK 3.3V Backlight (HIGH = on)
SCK GPIO18 SPI Clock
MOSI GPIO23 SPI Data out
DC GPIO15 Data/Command select
RST GPIO27 Hardware reset
CS Not used (always selected)

Key concepts: - SPI communication: ESP32 acts as master, clocks data out on MOSI with SCK - The DC pin differentiates commands from pixel data - No CS pin — display is permanently selected - Correct SPI mode (MODE 3) is critical - Adafruit_ST7789 + Adafruit_GFX libraries handle command sequencing

Wiring caution: Avoid GPIO12, GPIO0, GPIO2 as they affect boot mode. The pinout above uses all safe GPIOs.

MQTT IoT Telemetry Pipeline

The telemetry pipeline covered here is: - ESP8266/ESP32 as the sensor node - BMP280 temperature/pressure sensor - Mosquitto MQTT broker - Python subscriber on the backend

Architecture: Sensor → ESP32 → Wi-Fi → MQTT Broker → Python subscriber → data processing.

Servo Motor Control

A servo motor controlled via a rotary angle sensor on the ESP32: - Uses PWM (LEDC peripheral) to drive servo - Rotary sensor (potentiometer) read via ADC - Mapping sensor values to servo angles (0–180°)

Additional Reference Topics

  • Display library setup — installing Adafruit_ST7789 / Adafruit_GFX under PlatformIO and the Arduino IDE
  • Board pinouts — pin maps for the ESP8266/ESP32 dev boards usually paired with this display
  • Panel datasheets — what to read off them: controller, resolution, supply voltage, SPI mode

Why ESP32?

  • Built-in Wi-Fi/BT — no external modules needed
  • Dual-core — run networking on one core, application on the other
  • Deep sleep — microamps in sleep mode for battery-powered projects
  • Arduino + PlatformIO — beginner-friendly toolchain
  • ESP-IDF — production-grade SDK for advanced use
  • Rich peripheral set — enough for most IoT and embedded projects

Getting Started

  1. Install PlatformIO in VS Code (or Arduino IDE + ESP32 board package)
  2. Wire your ESP32 to the ST7789 display using the pin table above
  3. Install Adafruit_ST7789 and Adafruit_GFX libraries
  4. Run a basic sketch that fills the screen with color
  5. Progress to text rendering, shapes, and sensor data display

Pin Safety Reminder

Some ESP32 GPIOs affect boot behavior: - GPIO0 — boot mode select (pull low for flash mode) - GPIO2 — strapping pin, must be high for normal boot - GPIO12 — flash voltage selection - GPIO15 — strapping pin (also used here for DC — safe post-boot)

Always use safe GPIOs for display and sensor connections.

To-do

Status: incomplete. Still to write:

  • Write the ST7789 display section in full: a complete sketch (SPI init, ST7789 at SPI MODE 3, fill-screen, text and shapes) and the wiring diagram — currently only a pin table and concept bullets exist.
  • Write the BMP280 → ESP32 → Mosquitto → Python subscriber telemetry pipeline end to end: firmware publish code plus the Python subscriber that consumes the topic.
  • Write the servo control example: LEDC/PWM setup, ADC read of the rotary angle sensor, and the value mapping to 0–180°.
  • Replace the 'Additional Reference Topics' list with real content: Adafruit_ST7789/Adafruit_GFX installation under PlatformIO and the Arduino IDE, the ESP8266/ESP32 board pinouts, and the panel datasheet values (controller, resolution, supply voltage, SPI mode).
  • Add the display and sensor sections to 'Topics Covered' as written sections — the heading currently carries only pin roles and key concepts.