Free I/O Pins on 30b?

[Katie Wasserman]

The AT91SAM7L128 inside the HP30 has plenty of i/o pins but alomst all are used to drive the LCD.

Here's the SDK from HP. It's for the 20b but the 30b is electronically identical. If you take a look at the schematic in the zip file you'll see that there are 8 unused, general purpose digital i/o lines brought out to a header (actually just PCB pads), 4 ADC inputs, the JTAG lines and serial debug/programming lines. It's kind of limited for use as microcontroller and it doens't have USB communications built into the processor.

However there are been some projects that use the 20b/30b in the way that you suggest. Take a look
here for some more info.