STM32 vs ESP32: which should your product use?

The short comparison

What matters	STM32	ESP32
Made by	STMicroelectronics	Espressif Systems
Processor	32-bit Arm Cortex-M	Xtensa on the ESP32 and ESP32-S3, RISC-V on the ESP32-C3
Wireless on the chip	Not on most parts	Wi-Fi and Bluetooth
Best at	Control with hard timing	Devices that have to connect
Usual software	C with ST’s own tools, or the real-time system of your choice	ESP-IDF, Espressif’s framework, built on FreeRTOS
Long-term supply	A rolling 10-year longevity programme	A 12-year commitment on most chips and 15-year on the original ESP32, from dates Espressif lists
Radio approval	Yours to arrange if you add a radio	Espressif publishes certificates, such as FCC and CE, for its modules

Choose an ESP32 when the product has to connect

If the device needs Wi-Fi or Bluetooth anyway, an ESP32 puts the radio and the processor on one chip, with one firmware to write. There is room for real work beside the radio: the ESP32-S3 has two Xtensa LX7 cores at up to 240 MHz, and the ESP32-C3 has one RISC-V core at up to 160 MHz. Espressif publishes radio certificates for its modules, which can shorten the approval of your product. Ask your test house what your market still needs from you.

SceneScribe shows the pattern. Its cane carries an ESP32 that joins a Wi-Fi access point the headset creates, and handles obstacle detection, so the two pieces find each other without any other equipment.

Choose an STM32 when timing is the job

If the device has to turn a motor, close a control loop or sample a sensor on an exact schedule, start with an STM32. On an ESP32 the Wi-Fi stack shares the processor with your code, so a busy radio can move your timing. On a chip with no radio, the only code competing for time is your own.

SKYLOCK’s physical system uses STM32 control hardware. A gimbal that has to stay on a moving drone is exactly the kind of job this chip family is chosen for. Many flight controllers for drones run on STM32 chips too, for the same reason.

When to use both

For many products the answer is one of each. The STM32 runs the control loop, the ESP32 runs the network, and a serial link such as UART or SPI joins them. A Wi-Fi fault then cannot stall a motor. The price is two firmwares, two update paths and a message format you have to define and test. Espressif also publishes AT firmware, which lets a host chip use an ESP32 like a modem, with simple text commands.

Where a Raspberry Pi fits

A Raspberry Pi is a small Linux computer, not a microcontroller. A Raspberry Pi 5 has four Arm Cortex-A76 cores at 2.4 GHz, which is the right tool when a system needs a camera pipeline, a full operating system or AI on board. HARP is built around a Raspberry Pi 5, and ReFlex runs its grip model on one. A Raspberry Pi usually sits above a microcontroller rather than in place of one: Linux decides what to do, and the microcontroller does it on time.

Five questions that settle it

1. Does the product need a radio at all?
2. What is the tightest deadline in the system, in microseconds or milliseconds?
3. Does it run from a battery, and how many hours does it need between charges?
4. How long must you keep buying this exact part? Check the part number, not only the family.
5. Who will maintain the firmware, and which tools do they already know?

If you are not sure, send us the answers. Choosing the chip is part of our hardware work, and the firmware source is yours at handover.