Once you have a lot of your projects around the world, you wish to have a kind of tool for debugging, adjusting and testing. This terminal has a lot of dedicated modes of operation, each of them for specific unit, so it's hardly that it can be useful for anyone but me. But yet I publish it here, just to tell how good it is to take some time and build such tool.
It has 8×2 character LCD, six status LEDs, numeric keypad, RS232 and current loop I/Os, and one 2-bit parallel TTL port which is defined by software. Not much, but it lets me test my units in low level, just sending primitives and reading statuses - without servers and its software, which is always full of bugs.
And the last, but not the least - there is externally accessible ICSP port, so I can easily upgrade the firmware "on the fly".
It's in a compact 128×65×23 mm enclosure, easy to take with me wherever I travel.