I2c Keypad

Ron Czapala

Testing how the schematic appears on the forum...

This object uses the Interrupt-On-Change feature of the Microchip MCP23008 I/O Expander chip to interface a 4x4 Matrix Keypad (Parallax #27899) to a propeller MCU.
See Microchip's Application Note AN1081 at [URL]http://ww1.microchip.com/downloads/en/AppNotes/01081a.pdf[/URL]
When a key on the keypad is pressed, the MCP23008 goes LOW and the propeller scans the rows and columns to determine which key is pressed.
Then it clears the interrupt as the key is released.

             ┌───┐   ┌───┐   ┌───┐   ┌───┐
        ┌────┫ 1 ┣───┫ 2 ┣───┫ 3 ┣───┫ A │
        │    └─┳─┘   └─┳─┘   └─┳─┘   └─┳─┘
        │    ┌─┻─┐   ┌─┻─┐   ┌─┻─┐   ┌─┻─┐  K
        │ ┌──┫ 4 ┣───┫ 5 ┣───┫ 6 ┣───┫ B │  E
        │ │  └─┳─┘   └─┳─┘   └─┳─┘   └─┳─┘  Y
        │ │  ┌─┻─┐   ┌─┻─┐   ┌─┻─┐   ┌─┻─┐  P
        │ │ ┌┫ 7 ┣───┫ 8 ┣───┫ 9 ┣───┫ C │  A
        │ │ │└─┬─┘   └─┬─┘   └─┬─┘   └─┬─┘  D
        │ │ │┌─┻─┐   ┌─┻─┐   ┌─┻─┐   ┌─┻─┐
        │ │ ││ * ┣───┫ 0 ┣─┳─┫ # ┣───┫ D │
        │ │ │└─┳─┘   └─┳─┘ │ └─┳─┘   └─┳─┘
        │ │ │  │       │   │   └─┐ ┌───┘
        │ │ │  │       └───┼───┐ │ │
        │ │ │  └───────────┼─┐ │ │ │
        │ │ └────────────┐ │ │ │ │ │
        │ └────────────┐ │ │ │ │ │ │
        └────────────┐ │ │ │ │ │ │ │
                     8 7 6 5 4 3 2 1
            ┌──────┫ │ │ │ │ │ │ │
            ┣──────┼─┫ │ │ │ │ │ │    
        10k ┣──────┼─┼─┫ │ │ │ │ │
            ┣──────┼─┼─┼─┫ │ │ │ │   
            ┣──────┐ │ │ │ │ │ │ │ │   
            │    ┌─┴─┴─┴─┴─┴─┴─┴─┴─┴─┐   ─ GP7 thru GP0 (GP7 thru GP4 are pulled high with 10K resistors)
            │    │ +                 │
            │    │                   │
            │    │•    MCP23008      │
            │    │                   │
            │    │                 - │
            │    └─┬─┬─┬─┬─┬─┬─┬─┬─┬─┘
            │      S S A A A R   I │
            │      C D 2 1 0 E   N │
            │      L A │ │ │ S   T │
            │      │ │ └─┻─┻─┼───┼─┻────VSS
            └─┳────┼─┼────┳──┻───┼──────VDD
              └──┫ ┣──┘      │      3.3V
               4.7k│ │4.7k       │
                   │ │           │
                   
                    Propeller pins  

Ron Czapala

Added the code to the OBEX

http://obex.parallax.com/object/750

mklrobo

interesting,usage of the IC2 protocol. What is your overall goal? I have used telephones, that, I think, use the IC2 protocol.
The meridian system, with Norstar phones. The phones are dummy terminals, when the real "phone" in a securred place.
What are going to do with your system?

Ron Czapala

mklrobo wrote: »

interesting,usage of the IC2 protocol. What is your overall goal? I have used telephones, that, I think, use the IC2 protocol.
The meridian system, with Norstar phones. The phones are dummy terminals, when the real "phone" in a securred place.
What are going to do with your system?

I used it to built my alarm system - http://forums.parallax.com/showthread.php/155592-Hackaday-Alarm-System-Propeller-keypad-(w-MCP23008)-LCD

mklrobo

10-4. Good job! nice work. I have not seen your code to process the I/O. There is a way to use PLC code with the
propellers, as was stated in one of the other threads(forgot which one, right now). PLC code is easier to troubleshoot, and is used in industrial settings.
Good job!

Ron Czapala

mklrobo wrote: »

10-4. Good job! nice work. I have not seen your code to process the I/O. There is a way to use PLC code with the
propellers, as was stated in one of the other threads(forgot which one, right now). PLC code is easier to troubleshoot, and is used in industrial settings.
Good job!

Thanks! Here is a link to an early version of the code http://forums.parallax.com/attachment.php?attachmentid=108864&d=1401156181