PIC Programmer using USB Keyboard

[Raven Luni]

Greetings,

Needing something to program my PICs with I had the idea of ripping the guts out of an old keyboard and using the LEDs as the serial output (writing a program to make them dance for a bunch of data is easy).

Here is my initial design:


According to the specs an ATX supply should do nicely since it has 5V and 12V lines and the minimum spec for high voltage programming is VDD + 3.5 - a far cry from the 13V people seem to think is crucial.

LED outputs are assigned as follows:
Num Lock: Clock
Caps Lock: Data
Scroll Lock: Verify (off = load)

The CAPS button on the right isnt really a button - its just the column and row points for the caps lock key. This means that the PIC can set the caps lock status when verifying and the loader program can read it.

I've made a few assumptions with regards to things like the LED connections. I'll have a better idea once I have a proper look at an old keyboard. Polarities might be different, transistors might need to be PNP etc. but hopefully theres enough to go on for now and generate some feedback.

So - what you think?

 

[Raven Luni]

Corrected: Pin 13 (RB7 / DATA) still had to be connected to the CAPS output via another transistor

 

[Raven Luni]

Also probably better off using a 'normal' key for feedback since caps is a toggle

 

[BobK]

Interesting idea. Basically, using the LEDs on your keyboard as a SPI port.

Bob

 

[Raven Luni]

I've decided to make a new thread in projects for the actual build (there are a number of differences to the concept in here)

 

[mheee09]

See this helpful post Pic18f2550 usb device, make your own device!

 

[Raven Luni]

Cool. Thats for an already programmed pic to use the usb protocol though. This is for an unprogrammed device getting its data for the first time with no tools.

Thanks though - I might refer to it for future projects.