The Seeed XIAO ESP32-C3

The ESP32-C3 on a thumbnail: 21 by 17.5 mm, fourteen pads, a USB-C socket and no LED of its own to blink.

What it is

The same RISC-V chip as the ESP32-C3-DevKitM-1, at 160 MHz, on the XIAO family's outline: seven castellated pads down each long edge, 0.6 inch apart, so it pushes into a breadboard across the channel. The USB goes to the chip's own USB port, and that is what Serial and the serial monitor use.

The pin numbers are the XIAO's

The silkscreen numbers are the XIAO family's, not the chip's, and sketches for this board use them: D0 to D10 and A0 to A3 are defined for you.

Pad	GPIO	Also
D0	2	A0
D1	3	A1
D2	4	A2
D3	5	A3, see below
D4	6	I2C SDA
D5	7	I2C SCL
D6	21	UART TX
D7	20	UART RX
D8	8	SPI SCK
D9	9	SPI MISO, the BOOT button
D10	10	SPI MOSI

With the USB at the top, D0 to D6 run down the left and 5V, GND, 3V3, D10, D9, D8 and D7 down the right. 5V and 3V3 are supplies for the breadboard.

A0 to A2 are ADC1 channels 2 to 4 and read the net. The board prints A3 beside D3, but GPIO 5 is on ADC2, and ADC2 is not modeled, so analogRead(A3) reads 0 here. Use A0, A1 or A2.

There is no user LED

The one lamp on the board belongs to the battery charger. There is no LED_BUILTIN, so a sketch that uses it does not compile, which is more honest than one that blinks nothing. Wire an LED and a 220 ohm resistor to a pad instead; the built-in Blink uses D10.

The BOOT and RESET buttons are buttons, not pads. BOOT grounds GPIO 9, which is D9.

WiFi

It joins Mokxi's simulated network, with the network name and password as properties of the board. There is no radio, no 802.11 and no real internet: Simulated WiFi says what is faithful and what is not. The antenna socket is drawn and does nothing.

What is modeled

The DevKitM-1 model's chip, whole: the RISC-V core, GPIO and IO_MUX, UART0, the SYSTIMER, ADC1 and LEDC PWM on any pin, at the real addresses. Programs built for this board run on the DevKitM-1 and the other way around; the two carry different program strings so each is offered its own examples.

What is not modeled

ADC2, the battery charger and its pads on the back, the USB stack (Serial reaches the monitor directly), Bluetooth and a real radio.

Starter project

XIAO C3 knob is the board across a breadboard with a potentiometer on A0 dimming an LED on D10, and the reading printed in millivolts.