Woodstock Low Power

[PANAMATIK]

HP-25 Emulator and real HP-25 calculator can communicate!

Today I connected my HP-25 PC Emulator application with my HP-25E ACT calculator via USB/serial converter. The intention was to test the interface between the PC and the coming HP-25 Low Power. Because the latter is not yet there, I used an HP-25E. I added a serial interface to the HP-25 emulator application and the corresponding interface into the HP-25E firmware.

Now when the converter is attached and you click one of the PC emulator buttons the real calculator gets the key code and calculates! It is like pressing the original keys, also when you hold down the SST key it behaves like holding down the SST on the real calculator until released. Also when you press a real calculator button, the LED display contents will be shown on your PC.

This is not the main goal I wanted to achieve, but a nice addendum. Mainly the interface will be used to upload/download programs and data (yes, in both directions) between the PC and the huge 512k flash memory of the HP-25 LP circuit. I programmed these routines already, but cannot test them until I get the first prototypes next week.

The PC HP-25 emulator program will be updated to contain all Classic/Woodstock/Spice calculators in one application. If you switch from one calculator to another on the real calculator, automatically there will appear this calculator on your PC.

I got a slight headache to solve a problem when writing a single HP-25 program into the flash area, while keeping the other programs as they are; a normal procedure. But not with a small PIC processor, because a complete 4kB flash area must be erased before you can write 49 bytes to it. The previous 4k contents has to be read first, then altered, and written back into the flash. But the PIC does have only an 80 byte RAM buffer! I solved the problem.

If all goes well, the HP-25 LP will become a unique calculator.

Bernhard