STM32 or ESP32 for a connected device: how to choose?

Choose first on radio and power supply. The ESP32 integrates Wi-Fi and Bluetooth: it suits a device on a local network with a permanent power supply. STM32 is a broad family of Arm microcontrollers, including low-power series, suited to battery-powered devices or industrial constraints.

Which radio does your device use?

This is the first criterion.

• Espressif's ESP32 integrates Wi-Fi and Bluetooth on the same chip, depending on the variant. It avoids a separate radio module when the device connects to a home router or a company network.
• STMicroelectronics' STM32 are mostly microcontrollers without a radio, paired with an external module (Wi-Fi, Bluetooth Low Energy, LoRa, LTE-M). Some series integrate a radio, such as STM32WB for Bluetooth Low Energy or STM32WL for sub-GHz networks such as LoRa.

For a device that mainly talks Bluetooth Low Energy to a smartphone, other chips are also worth considering, such as Nordic Semiconductor's nRF52 family.

Does your device run on batteries?

Wi-Fi draws much more power than Bluetooth Low Energy or LoRa. An ESP32 on Wi-Fi suits a device with a permanent power supply. For a battery-powered device that must last, a low-power STM32 series paired with a frugal radio leaves more headroom. Real consumption depends mostly on the firmware: wake-up frequency, connection time, peripheral sleep modes. It is measured on the prototype.

Which tools and ecosystem?

• ESP32: Espressif's ESP-IDF development framework, based on FreeRTOS, with ready-made Wi-Fi and Bluetooth libraries.
• STM32: ST's STM32Cube tools, and a very wide range of parts, from the simplest to the most powerful. The real-time OS is your choice: FreeRTOS, Zephyr or bare metal.

Both families are also supported by Zephyr, which makes a later change of chip easier.

What about availability and lifetime?

For a product sold over many years, check part availability with distributors and the longevity commitment each manufacturer publishes for its products. Plan a hardware abstraction layer in the firmware from the start: a component change then costs less.

And radio compliance?

A pre-certified radio module simplifies compliance testing under the RED directive, but does not remove it: the finished product is what gets assessed. Since 1 August 2025, the RED also sets cybersecurity requirements for internet-connected radio equipment. For a specific case, contact a test laboratory or a regulatory adviser.

How we can help

Picodev develops firmware on STM32, ESP32, PIC and nRF52, and helps you choose the chip and the radio for your device's use.

Related service: Embedded software