In order to work with the calculator at the firmware level, certain hardware and software are required. Hardware needed is listed below.
1) HP 20b Business Consultant Financial Calculator.
2) JTAG Header Connector and JTAG Emulator Device
3) RS232 Cable.
A header is required to connect the calculator to the JTAG Emulator. The HP 20b has solder pads on its PCB but is missing the connector.
Some sources for the connector are:
A connector or wires to an external connector must be soldered to the PCB of the HP 20b. Need to add instructions or link to instructions here! ««
I advise that you 'open' the bottom of the calculator to leave room for the JTAG header. You can use a box cutter (or a router if you are more fancy) to cut out a 1.25“ long opening at the bottom of the calculator. This opening should be in the receded area at the bottom of the calculator, centered and the hight of the receded area. you can then open the calculator, solder the JTAG header and close the calculator in order to be able to keep using it while having an easy JTAG access.
A JTAG interface device is required to communicate with the Atmel AT91SAM7L128 ARM Microcontroller (ARM7TDMI core). Some options are: