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+--- Thread: Free I/O Pins on 30b? (/thread-212.html)
Free I/O Pins on 30b? - jwm - 12-23-2013 12:41 AM
Hi, I was wondering how many free I/O (can be configured for input or output) pins I can easily solder to on the HP 30b board? I aquired a few and after making some WP-34s, I'd like to use the rest as general development boards, sort of like arduino is used but with a nice and useful keyboard and display built in and faster processor which can be handy for some projects.
My other idea is to turn them into USB numeric keypads/programable keypads. I purchased one of these ( http://www.amazon.com/HP-Calculators-COMBINATION-CALCULATOR-NUMERIC/dp/B002J6BUEI ) thinking HP Calculator, can't go wrong. How wrong I was. Worst HP product I have encountered. Implementing the idea properly out of a 30b seems like a fitting penance for that purchase.
John
RE: Free I/O Pins on 30b? - Katie Wasserman - 12-23-2013 01:48 AM
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.
RE: Free I/O Pins on 30b? - jwm - 12-23-2013 04:50 AM
Ah cool. That is more than I thought I'd have actually plus ADC. nice.
for the USB keyboard idea I was thinking of just using an atmega32u4 board (teensy, arduino nano, adafruit breakout) and having it talk serial to the rest of the calculator and install it similarly to the available usb mod board.
Bit banging a USB client on the arm wouldn't be too hard, but without a stable crystal controlled clock I don't think it is feasable.
RE: Free I/O Pins on 30b? - Katie Wasserman - 12-23-2013 05:56 AM
Quote:but without a stable crystal controlled clock I don't think it is feasable.
Take another look at the schematic in the SDK and look at the PCB, you'll see that there's a place for a 32KhZ crystal. Although it's nowhere need the speed you need for USB you can use that clock to calibrate the main clock and probably get an accuracy good enough for bit-banged USB. However you're Sparkfun breakout board solution would certainly be easier all around.