24 October 2008

FT817 keypad - circuit diagram

Now that the keypad firmware has reached a usable state, here is the schematic diagram I am about to implement.

The development version ran on the internal clock set at 1 MHz, but it was inaccurate enough that serial communication was not possible at 9600 bps. Since reproducibility of this project is a must, I prefer to distribute a code that relies on an external, more accurate, clock source.

Keypad lines are labeled according to the top-most or left-most key of the column/row. You will need to check the pin layout of your keypad in a datasheet or with an ohmmeter (pressing keys until you map the 8 pins). On mine were exactly in the required order C1 to R* from left to right (looking at the keypad as if you were using it).

LED current flows into the chip, and don't forget to connect the resistor to the +5V line.

Pins on the ACC socket (MiniDIN 8 pins) are labeled as shown on the FT-817 manual.

That's all. If you are equipped to program an ATtiny2313 and need the firmware, just drop me a line. If you want a programmed and tested controller chip, do not hesitate to contact me either! mycall at yahoo.com ("mycall" is the first part of this blog URL, also written on the blog name...). If you need a customized keypad firmware with different key mappings or presets, I'm here to help.