A Cheaper Single-Core ESP32 Module?

The single-core ESP32-S0WD finally has a module to call its own

Alasdair Allan
3 min readJul 6, 2018

Despite initial rumours, the Espressif ESP32 was never supposed to replace their widely used, and much cheaper, ESP8266 chip. In just over four years, the ESP8266 has gone from an obscure Serial-to-WiFi module with no English documentation to one of the three biggest communities around maker hardware.

Unfortunately, never intended for the many roles it was thrust into, the ESP8266 lacks basic features that make building a secure Internet of Things connected device using it practically impossible. The more capable ESP32 was designed to, amongst other things, solve that.

However with a more capability comes a higher price, and one of the biggest selling points of the ESP8266 is that it’s almost cheap enough to throw away. Which is a problem the new Espressif ESP32-SOLO-1 module might solve.

The ESP32-SOLO-1. (📷: Espressif)

About a year ago Espressif released a single-core version of the dual-core ESP32 chip. Called the ESP32-S0WD, the 5×5 mm 48-pin package is built around a single Xtensa 32-bit LX6 microprocessor, has 448 KB of flash and 520KB of on-chip SRAM, and can support up to 64MB of QSPI flash.

With one less core than the chip is less of a heavyweight than the ‘mainstream’ ESP32. But the lower specification also means a lower price per unit, and as it shares the same architecture—including security features like secure boot and flash encryption—of the other chips in the range, it’s a perfect fit for low powered connected devices that need the advantages of the ESP32 over the original ESP8266.

The ESP32-SOLO-1 specification. (📷: Espressif)

However, apart from Particle’s Argon board, so far we haven’t seen that much adoption of the ESP32-S0WD. The reason for this probably comes down to certifications. It’s much easier to get a board or product certified if you’re using a pre-certified wireless module rather than a bare chip, so if you wanted to use the ESP32 most people were choosing the dual-core version of the chip which was widely available as a module. Despite the expense. The arrival of the ESP32-SOLO-1 module is going to change that. A lot of connected devices don’t need the full power of the dual-core ESP32, and a single-core version will me more than “good enough” for them to build around. Less hefty, but lower priced, the new module might well push the single-cored version of the ESP32 to a much wider audience.

While you can pick up an ESP8266 based ESP-12F module for around $1.70 in low volume, or a bare ESP8266 chip for around $1.10. If you’re looking for a ESP32-WROOM-32 module the price you’ll pay is more like $4.00, with a bare dual-core ESP32 priced around $2.80. Although the single-cored version of the ESP32 is cheaper, you can pick it up around $2.40 in low volumes.

Not widely available yet, it’s unclear at what price point the new ESP32-SOLO-1 module will settle, but you can expect it to cheaper than its dual-cored cousin, and if the module proves popular we can expect the price differential between the single-cored and dual-cored version of the ESP32 to widen as volume production drives down the cost.

If you’re thinking of building a project or a product around the Espressif chip, and don’t need the power of the dual-core version of the ESP32, then you should take a serious look at the new ESP32-SOLO-1 module instead of going straight for an ESP8266. The chip-level security you gain is worth an extra dollar on your Bill of Materials, if only to avoid becoming the next security horror story.