May 28, 2026 Contents Hardware Identifying and soldering the connectors Testing the UART JTAG Software Configuring OpenOCD Dumping the address space Firmware disassembly and analysis Relinking the firmware Patching the firmware More firmware analysis Making my changes Buttons LEDs Building an API My code Fixing bypass gain Flashing the new firmware Firmware update format Applying the update Future directions MIDI 2 property exchange Custom DSP effects Combined “mega-firmware” Overall thoughts I’m having a lot of fun with reverse engineering lately, so when I was looking over the service manual for my guitar amp, a Yamaha THR10c, and saw references to a UART header in the schematic, I got excited. I wondered if anything cool was hiding in there. Next to it was a JTAG header. I knew next to nothing about JTAG, but had heard the name before associated with hardware hacking, so maybe that would be useful as well.…