I've recently found that there's 4 terminals on my old electronic dictionary, each labeled as "/RP TXD RXD GND". The dictionary is more than 5 years old, and runs on 1xAA battery. Is there any chance I could make serial connection to the device with RPi and do something like reprogramming? I'm afraid it's too old and low-powered, but I thought giving it a try could be fun...
You'll have to check the voltage on the TXD and RDX lines. The Pi only allows upto 3.3V.
Other than that you can just connect the TX on the Pi to the RX on the dictionary, and vise versa, and the connect the 2 grounds (GND).
I don't think you can reprogram it though. But you might be able to see the boot process. Maybe even add words or something.
Sound like a fun exercise.