ESP32

Why it still matters

Ten years after launch, the original ESP32 is beaten on almost every individual specification by something newer in the family. It has no Wi-Fi 6, no BLE 5, no 802.15.4, the highest active current, and an instruction set Espressif has stopped designing new parts around.

It nonetheless remains a defensible choice, for three reasons that no newer part fully replaces.

It is the only ESP32 with Bluetooth Classic — specifically BR/EDR alongside LE 4.2. If your product needs to pair with a phone as an A2DP audio sink, act as a hands-free device, or talk to legacy Bluetooth serial equipment, the original ESP32 and the very new S31 are your only options in the family. Every part in between is Bluetooth LE only.

It has an on-chip Ethernet MAC. Add an external PHY such as the LAN8720 or IP101GRI and you have wired 10/100 networking with no SPI-to-Ethernet bridge chip and no bandwidth bottleneck. Until the P4 and S31, no other ESP32 offered this.

The ecosystem depth is unmatched. A decade of Arduino libraries, tutorials, Stack Overflow answers, ESPHome configurations and commercial reference designs targets this specific chip. When something goes wrong at 2 a.m., that matters more than a datasheet advantage.

Architecture notes

Two Xtensa LX6 cores run at up to 240 MHz, and unusually for this family they are not symmetric in practice: by convention ESP-IDF pins the Wi-Fi and Bluetooth stacks to one core (PRO_CPU) and leaves the other (APP_CPU) for application code. This is a genuine advantage over the single-core C-series parts, where radio housekeeping and your application contend for the same core.

Alongside them sits an ULP co-processor — an 8 MHz finite-state-machine design, not a general RISC-V core as on later chips. It can poll an ADC or a touch pad and wake the main cores on a threshold, but programming it is awkward compared with the LP cores on the C5, C6 and P4.

The 520 KB of SRAM is the largest in-package figure in the family, but it is fragmented across regions with different access rules, and a meaningful slice is consumed by the Wi-Fi and Bluetooth stacks. Enabling Bluetooth Classic and Wi-Fi simultaneously leaves considerably less free heap than the raw number suggests.

Peripherals worth noting

• 34 GPIOs, but a substantial number are input-only or strapping pins, and GPIO 6–11 are connected to the SPI flash and unusable. The practical count is well below 34.
• Two 8-bit DACs — the only ESP32 parts with true analogue output are this one and the S2.
• 10 capacitive touch channels, and an 18-channel 12-bit ADC. The ADC is notoriously non-linear and conflicts with Wi-Fi on ADC2; calibrate it, and prefer ADC1.
• TWAI (CAN 2.0) and an SDIO host and slave interface.
• 8 RMT channels with flexible TX/RX assignment, which is why so many addressable-LED projects target this chip.
• No USB. Programming is over UART, so boards need a CP2102 or CH340 serial bridge.

Modules and boards

The dominant module is the ESP32-WROOM-32E (from $2.50), with the -32UE variant substituting an external antenna connector for the PCB antenna. If you need PSRAM, the ESP32-WROVER-E (from $2.80) adds it. The ESP32-MINI-1 (from $2.30) is the small-footprint option, and ESP32-PICO-MINI-02 (from $3.50) is a system-in-package that shrinks the external component count further.

For development, the ESP32-DevKitC is the reference board; ESP32-PICO-KIT-1 costs $10. The third-party ecosystem is enormous — NodeMCU-32S, Wemos/LOLIN D32, the AI-Thinker ESP32-CAM (~$10, still the cheapest way to get a networked camera), WT32-ETH01 for Ethernet, and the LoRa-equipped TTGO and Heltec boards.

Choose it when

• You need Bluetooth Classic — A2DP audio, HFP, or SPP to legacy equipment
• You need wired Ethernet on a budget
• You are maintaining or extending an existing ESP32 design
• You want the maximum amount of copy-pasteable prior art

Choose something else when

• You are starting fresh and want modern radios → ESP32-C6
• You need a display, a camera, or on-device ML → ESP32-S3
• Battery life is the primary constraint → ESP32-C6 or ESP32-H2
• You want the lowest possible unit cost → ESP32-C2 or ESP32-C3