Which ESP32 board? Classic, S3, C3 and C6 compared for makers

ESP32 isn’t one chip. The S3, C3 and C6 you see in shops are different chips that differ in cores, radios, USB and pin count. Pick the wrong one and some projects simply can’t be built, such as buying an S3 for a Bluetooth speaker that needs Bluetooth Classic. This lesson compares the four you’ll meet most often, using Espressif’s own data, then works through choosing for real projects.

Four chips in one table

Figures are for the chip itself (from Espressif); a given board may not break out every pin.

	ESP32 (original)	ESP32-S3	ESP32-C3	ESP32-C6
Cores	Dual Xtensa LX6	Dual Xtensa LX7	Single RISC-V	Single RISC-V + low-power core
Max clock	240 MHz	240 MHz	160 MHz	160 MHz (LP core 20 MHz)
Wi-Fi	802.11 b/g/n (Wi-Fi 4), 2.4 GHz	Wi-Fi 4, 2.4 GHz	Wi-Fi 4, 2.4 GHz	Wi-Fi 6, 2.4 GHz
Bluetooth	Classic (BR/EDR) + BLE, v4.2	BLE 5	BLE 5	BLE 5
Thread / Zigbee (802.15.4)	No	No	No	Yes
USB on the chip	None (boards use a USB-UART bridge)	USB OTG + USB Serial/JTAG	USB Serial/JTAG	USB Serial/JTAG
GPIO (chip)	34	45	22	30
SRAM	520 KB	512 KB	400 KB	512 KB

Other differences: the original ESP32 has two 8-bit DAC channels and 10 touch pins. The S3 has no DAC but 14 touch pins, plus vector instructions that speed up signal processing and small neural networks. The C3 has neither DAC nor touch.

Bluetooth: Classic is only on the original

There are two kinds of Bluetooth, used for different jobs:

• Bluetooth Classic (BR/EDR) carries audio (speakers, headphones) and older serial-style devices.
• Bluetooth LE is low power: sensors, buttons, remotes, talking to a phone app.

Of these four, only the original ESP32 does Classic. The S3, C3 and C6 are LE only. If the project is a speaker or receives audio from a phone, it has to be the original.

Native USB: OTG and Serial/JTAG are not the same

• The original ESP32 has no USB on the chip. A DevKit therefore carries a USB-to-UART bridge chip next to the connector for flashing and the serial monitor. Some computers need the bridge chip’s driver installed first.
• USB Serial/JTAG (S3, C3, C6) is a fixed-function USB block inside the chip. One USB cable gives you flashing, a serial monitor and JTAG debugging, but it can’t be turned into any other kind of USB device.
• USB OTG (on the S3) lets the board be many kinds of USB device: a keyboard or mouse (HID), a MIDI device, or a flash drive (MSC). This is the chip for a macro pad or a game controller that just works when plugged into a computer.

USB takes two GPIO pins. The C3 uses GPIO18 and GPIO19; the S3 and C6 have their own fixed pins. If you use the built-in USB, those two pins are not available for anything else.

C6: Wi-Fi 6 and the smart home

The C6 is the only one of the four with Wi-Fi 6 (802.11ax at 2.4 GHz) and an 802.15.4 radio for Thread and Zigbee, which suits smart-home devices that need to talk to those systems. It also has a separate low-power RISC-V core running at up to 20 MHz.

What doesn’t change: every chip in this lesson is 2.4 GHz Wi-Fi only, and the C6’s Wi-Fi 6 is at 2.4 GHz too.

Small boards vs DevKits

The same chip comes on boards of many sizes.

	DevKit	Small (thumb-sized) board
Pins broken out	Nearly all, e.g. ESP32-DevKitC 38 pins, ESP32-C6-DevKitC-1 32 pins	Fewer; check that board’s pinout
USB ports	Some have two (via a bridge, and the chip’s own USB)	Usually one
Breadboard	A 38-pin board leaves no free holes on one breadboard	Narrower, leaves holes for wires
Good for	Bench experiments, learning	Fitting inside a toy or a 3D-printed case

More on board width in the breadboard lesson. The board’s flash size matters if you plan to update firmware over Wi-Fi, because you need room for two firmware images; how OTA and rollback work is covered at 6amdev: ESP32 OTA updates without bricking.

Worked example: choosing from real requirements

Project 1: a 12-key macro pad that acts as a keyboard when plugged in

1. Count pins: 12 keys + 1 single-wire LED strip + 2 for an I2C OLED = 15 pins
2. Must be a USB HID device → needs USB OTG → ESP32-S3
3. Check pins: the chip has 45, minus 2 for USB, plenty left, but confirm the board you choose actually breaks out 15 usable pins.

Project 2: a battery temperature sensor that sends readings to a phone over BLE

1. Count pins: I2C sensor 2 + one button 1 = 3 pins
2. Needs BLE, no special USB → a small C3 board is enough
3. Check pins: 22 − 2 (GPIO18/19 for USB) = 20 on the chip, more than enough

Project 3: a plush speaker that plays music from a phone

1. Ordinary phone audio over Bluetooth uses Bluetooth Classic
2. → only the original ESP32 among these four

Project 4: a light switch that joins a smart home over Thread or Zigbee

1. Needs an 802.15.4 radio → C6

Start with “which feature do only some chips have?” (Bluetooth Classic, USB OTG, Thread/Zigbee) before counting pins or MHz. A missing feature can’t be added; missing pins just mean a bigger board.

Common mistakes

• Buying an S3 or C3 for a Bluetooth speaker. They have no Bluetooth Classic.
• Expecting a C3 to be a USB keyboard. Its USB does flashing, serial and JTAG only, not OTG.
• Counting GPIO from the chip spec. Small boards break out far fewer, some pins go to USB, and modules use some internally: the ESP32-WROOM-32E module offers up to 26 GPIOs from a chip with 34, because GPIO6–11 drive its flash.
• Feeding a 5 V signal into a GPIO. ESP chip pins tolerate 3.6 V; every chip here runs at 3.3 V.
• Blaming the board when flashing fails. First check the USB cable isn’t charge-only, and that an original-ESP32 board’s bridge driver is installed.
• Expecting 5 GHz Wi-Fi. Every chip here is 2.4 GHz only.

Sources

• Chip Series Comparison (ESP-IDF v5.0) — Espressif
• ESP32-C6 product page — Espressif
• ESP32-S3 product page — Espressif
• USB Device Stack for ESP32-S3 — Espressif
• USB Serial/JTAG Controller Console (ESP32-C3) — Espressif
• ESP32-WROOM-32E Datasheet — Espressif