Wednesday, September 5, 2007

Symbolics keyboard to PIC, step 1

The first step is to connect the Symbolics keyboard to the PIC. I am using the 16F690 which comes with the PICkit 2 starter kit on the low pin count demo board (Microchip DM164120-1). The keyboard cable mates to a 6-pin modular jack (such as Digikey part number 609-1061-ND), which I tacked onto the side of the board. Unfortunately, this mod jack has pin spacings of 50 mil "horizontally" between successive pins, so I bent up the odd pins and soldered the even pins to the demo board.





































Mod jack pinKeyboard functionPIC functionPIC pin marking
6GND
5GND (N/C)
4Vdd
3Key DataRX/DTRB5
2CLKTX/CKRB7
1/CLRRC5RC5

My first task will be to power up the keyboard, code a scanning loop, and try to detect keystrokes for a single key, such as the Left Control Key, displaying the count of key-down events in binary to the LEDs connected to RC0-RC3. If the keyboard is not debounced by the internal microcontroller, the count will not increment cleanly, but I hope to at least prove that I can talk to the keyboard and make sense of what comes back. I'm not sure how much current the keyboard will need, so I might have to power the demo board with an external supply.

[UPDATE: It turns out the standard numbering of modular jack pins is the reverse of the pin numbering of the P1 header inside the keyboard. I've corrected the table above to reflect the standard modular jack scheme. Looking into the opening of the jack, with the locking tab down, pin 1 is on the left side.]

1 comment:

  1. These pieces of my half-completed project may help you:

    http://www.asciilifeform.com/images/3.png

    http://lmkbd.googlecode.com/svn/trunk/

    ReplyDelete