The Hidden Microcontroller Inside a LoRa chip

If you’ve ever done anything with LoRa, the chances are you’ve used a LoRa chip or module as a peripheral for a microcontroller, and left it at that. But that’s not always the case. Rather than being a pre-programmed ASIC under the hood, the Semtech LR2021 has its own on-board microcontroller whose firmware can be updated. [Alex Beale] has managed to unlock its secrets.

The use of LLMs can elicit strong opinions at times, but in this case we agree with him that the task of reverse engineering this hidden microcontoller would have been a near-impossible task without their help. Having done so though,he can write custom firmwares, which he’s able to demonstrate. Running the required FFTs for a waterfall display on-chip for example is now possible, as is running your mesh network node on the chip itself.

This work continues a streak of recent discoveries unlocking software-defined radio functionality inside dedicated radio chips, with both WiFi and LoRa chips falling prey to reverse engineering. It’s an interesting time, if SDR is your thing.

Thanks [Notbasa] for the tip.