View Full Version : 19 key numeric keypads that has PS/2, Serial, and I2C interface available soon

Peter Jakacki
11-08-2011, 03:09 AM
I bought a whole heap of USB numeric keypads that were supposed to be PS/2 compatible but they are not. If I look for PS/2 compatible keypads they are much harder to get and much more expensive.

I pulled one of the USB keypads apart and found a cheap and nasty encoder pcb which is very easy to replace. So I designed a replacement low-cost pcb that I can retrofit to the keypad and in so doing I have added protocols for PS/2, asynchronous serial (duplex or half-duplex 1-wire), and I2C. Of course I am not supporting USB but the I2C option is good for the Propeller projects as you don't need to dedicate I/O for keypads and just use the EEPROM I2C I/O lines instead. The keypad can be addressed as a standard I2C device and you can even read the state of the keys as well as the keypad codes. The same goes for the serial protocols in that you don't need to dedicate a cog and even use simple serial in Spin.

I hope to have some pcbs back soon and I will still use the USB connector that comes with it as my systems accept this connector and normally deal with it in PS/2 protocol. Now however I will probably free up a cog and talk to the keypad as an I2C device. Future designs that need a keypad will just have P28,P29 on the USB A socket.

So if anyone is interested I will make both assembled PCBs and converted keypads available.

P.S. I could even get away with using a normal 3.5mm stereo jack plug and run this in 1-wire asynch serial which would do bi-directional serial with a pullup resistor on the line. The connector saves a lot of space for sure.