Open Things Wants to Replace Your Raspberry Pi Compute Module 3 with an Openthing 1 ESP-CM3

Designed to drop in to existing Raspberry Pi CM3 carrier board designs, this ESP32-S3-powered module is a low-cost alternative.

Berlin-based Open Things is aiming to produce a more affordable alternative to the Raspberry Pi Compute Module 3 (CM3) range, for projects which can get away with less raw computational performance — driven by an Espressif ESP32-S2 microcontroller.

"ESP32-S2 is a powerful and versatile computing device that can easily replace the Raspberry Pi Compute Module 3," argues Open Things' Mirko Häberlin. "At the core of this chip is a [Tensilica] Xtensa 32-bit LX7 CPU that operates at up to 240MHz, providing plenty of processing power for a wide range of applications. Additionally, it has built-in Wi-Fi and USB connectivity, making it easy to connect to the internet or other devices. It also boasts lower power consumption, which can be especially important for applications that require battery-powered operation."

Built atop an Espressif ESP32-S2-SOLO module, the Openthing 1 ESP-CM3 offers the aforementioned single-core 32-bit Xtensa LX7 processor running at up to 32MHz, a choice of 4MB or 8MB of pseudo-static RAM (PSRAM), and support for up to 4GB of external memory. Compared to a Raspberry Pi Compute Module 3+, which has a Broadcom BCM2837 system-on-chip (SoC) with four Arm Cortex-A53 cores running at up to 1.2GHz, 1GB of LPDDR2 RAM, and up to 32GB of eMMC storage, those are limited specifications — but enough, Häberlin says, for a range of interesting projects.

"Both devices feature multiple input/output (I/O) pins and protocols like I2C and SPI, which can be used to connect various sensors and other components," Häberlin notes. "Additionally, they both support programming using a variety of programming languages, including C++, Python, and others. Another key advantage to the ESP32-S2 is that it is available and affordable, while the Raspberry Pi Compute Module is widely unavailable due to a global parts shortage."

The Openthing 1 ESP-CM3, which is designed to drop into CM3-compatible carrier boards without modification, includes integrated Wi-Fi connectivity but no Ethernet PHY, a USB 2.0 On-The-Go (OTG) port, 45 general-purpose input/output (GPIO) pins including two I2C, two SPI, and one UART bus.

"The device comes without any firmware or software," Häberlin warns of the gadget, "primarily because we don’t know your project. Openthing 1 ESP-CM3 can run a variety of operating systems like Zephyr or MicroPython, which are easy to use. Overall, the ESP32 microcontroller board is an excellent alternative to the Raspberry Pi Compute Module 3, offering availability, powerful computing capabilities, and wireless connectivity."

Häberlin is planning to launch a crowdfunding campaign for the module soon via Crowd Supply, at an as-yet undecided but "affordable" price point, while design files for the board are available on GitHub under the CERN Open Hardware License Permissive 2.0 for the hardware and GNU General Public License 3.0 for the software.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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