minirobo.io

Episode #1 · ESP32-C3 SuperMini

The $5 Brain Behind Every Mini Robot

A single-core RISC-V microcontroller with Wi-Fi + BLE on a board barely bigger than a coin. For a huge number of mini robots, it's the only controller you'll ever need.

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Episode video — paste your YouTube ID to embed

What it is

The board I build with is the ESP32-C3 SuperMini — the ESP32-C3 chip (made by Espressif) on a board barely bigger than a coin, with USB-C and a row of pins down each edge. It's a microcontroller: a tiny computer that runs one program on a loop, forever, controlling things in the real world. Unlike a classic Arduino Uno, it has a single-core RISC-V CPU at ~160 MHz, plenty of memory, and built-in Wi-Fi and Bluetooth LE — so your robot can be driven from your phone with no extra parts.

A small stack of microcontroller boards on the edge of the workbench

A few dollars of robot brain, in the flesh.

The bare minimum to use it

  • It runs on 3.3 V logic — not 5 V. Power it over USB; never wire 5 V sensor signals straight into a pin.
  • The numbered pins are GPIO — read buttons/sensors, switch things on and off, and output PWM to drive servos and motors.
  • Program it with PlatformIO — describe the board once in platformio.ini, plug in over USB, run pio run -t upload.
  • Start with Blink — get the onboard LED flashing and you've used everything you need to begin building.
#1 beginner killer: 3.3 V logic. A 5 V signal wired into a GPIO pin can damage it. Check every sensor's voltage before connecting.

Wiring (Blink)

Nothing to wire — just power the board over USB-C. The onboard LED is on GPIO 8 on the C3 SuperMini, and it's active-low (lit when the pin is LOW). Upload the sketch below and it blinks.

USB-C ──▶ ESP32-C3 SuperMini
                  └─ onboard LED ── GPIO 8 (built-in, active-low)
ESP32-C3 SuperMini miniRobo pin map: servos on GPIO 3 and 4, motors on GPIO 5, 6, 7 and 10, onboard LED on GPIO 8

The C3 SuperMini pin map used across the miniRobo builds — keep it handy as you wire up later episodes.

The code

Classic Blink for the ESP32. Copy it in, or download the sketch from the sidebar.

// miniRobo EP1 — ESP32-C3 SuperMini Blink
#define LED 8            // onboard LED on the C3 SuperMini (active-low)

void setup() {
  pinMode(LED, OUTPUT);
  Serial.begin(115200);
  Serial.println("miniRobo: hello from the ESP32!");
}

void loop() {
  digitalWrite(LED, HIGH);
  delay(400);
  digitalWrite(LED, LOW);
  delay(400);
}

What I wish I knew

  • 3.3 V, always. Most of the cheap fried boards die here.
  • "Charge-only" USB cables will betray you. If your PC can't see the board, swap the cable before you panic.
  • You only get ~11 pins. A few are strapping pins (GPIO 2, 8, 9) the board needs at boot — save those for last.
  • Don't power motors from the board — use a motor driver like the DRV8833 with its own battery.
  • Upload stuck at "connecting"? Hold the BOOT button while it starts, then release.