In this video, Piers Finlayson takes viewers deep into the internals of Airfrog, a wireless co-processor for ARM microcontrollers. The key focus is Serial Wire Debug, a two-wire protocol that gives Airfrog the power to access RAM, flash, and peripherals on live ARM Cortex chips. If you’re curious about real-time microcontroller control, this tool delivers.
Airfrog uses a tiny ESP32 module to act as the host device. It takes control of the clock and data lines to communicate with a target microcontroller. Through Serial Wire Debug, it sends commands, waits for replies, and transmits or receives data—all while the target runs normally. This setup allows complete hardware access using just two GPIO lines.
Understand How It Works
Piers explains the Serial Wire Debug protocol step by step. First, the host sends a command. Next, the target responds with a status code. Finally, the host reads or writes the data.
The debug and access ports act as intermediaries. These ports allow Airfrog to reach RAM, flash memory, and even I/O pins. ARM’s system architecture makes this level of control possible, though features may vary between chips.
Code in Rust, Not Required
Airfrog’s firmware is written entirely in Rust using the Embassy async framework. Piers shows the exact function that manages Serial Wire Debug write operations. It controls the line states, sends bits, reads acknowledgments, and handles retries.
However, you don’t need to know Rust to use Airfrog. It offers both RESTful and binary APIs. You can interact with the hardware using any language or tool. Even web-based apps can control devices using JavaScript via the REST API.
The Hardware is Tiny
Airfrog’s brain is the ESP32C3 Mini-1 module. It handles Wi-Fi, timing, and debug tasks. The board includes just a voltage regulator and a few passives. Piers powers the unit with 5V, which it regulates to 3.3V for the ESP.
The entire device fits within an inch. Yet, it can reprogram a microcontroller’s RAM and flash live. It’s simple, effective, and fits on your bench without clutter.
