Comment by atoav
1 month ago
The absolutely "leetest" thing I have ever seen was a device where the firmware update was to be done by:
1. Hold a button while booting (pretty normal)
2. This reconfigures the circuit path of one of the LEDs so it is reverse-biased to VCC via its resistor and switches one of the microcontroller GPIOs to ADC input
3. You go to a website that plays a strobe pattern (encoding the firmware)
4. You hold that website in front of the LED till other LEDs blink, signifying a successful update
They could have done this using a photodiode, but no, they had to abuse an LED. Not many people are aware that LEDs can in a certain configuration be used to measure light.
Another example of firmware update reusing something that is already there: some electric guitar effects from TC Electronics can be reprogrammed by bringing a phone close to the guitar pickups. The phone app encodes the data as sound that is picked up by the guitar pickups and sent down the chain to the effect.
Ahh good example I remember having done that myself before!