Thread: Project help

  1. #1
    Registered User
    Join Date
    Feb 2006

    Project help

    My final year project at university is designing and building a user interface for a plug in electronic timer that will switch on an external load at a set time and switch it off again at a set time.

    I am using a 6808 processor and a 2x8 alphanumeric lcd display. I have 4 I/Ps, 2 of which are for a rotary encoder. I only know very basic C.

    Would anyone be able to help with the program or provide some links to good example programs? Especially for a program which would run and display a real time clock on an lcd display? Thanks

  2. #2
    Registered User fischerandom's Avatar
    Join Date
    Aug 2005
    Who designed the hardware?
    1. Test the hardware, i.e., write a char to the LCD, etc, and you can read the rotary encoder wheels on the bus. Stuff the data in a variable, declaring it volatile is a tip, though its probably not neccessary.
    2. Use the hardware manual for the Motorola 68xx processors. Read about timer registers. Then look in the manual for the C-compiler how to access the processors registers. Built a little Time structure, something like:
    typedef struct Time {
        unsigned char   hours, minutes, seconds;
    } Time;
    Access it with:
    Time   time;
    time.hours = value read from rotary wheel;
    time.minutes = other value read from rotary wheel;
    time.seconds = 0;
    3. You then setup a timer register in the 6808 to generate an interrupt every second.
    The interrupt shall trap a call to a Timer function that decrements time.seconds, etc.

    if ( time.seconds > 59 ) {
       time.seconds = 0;
       if ( time.minutes > 59 ) {
          time.minutes = 0;
         if ( time.hours > 23 )
            time.hours = 0;
            boom = true;
    and then. . .
    if ( boom )
                      SwitchRelay( ); /* etc. */
    4. You need a simple interface Set Timer / Run / Stop.
    And obviously a function to write to the LCD.
    5. Some hardware buttons Run/Stop. Preset, etc.

    Hope you get some ideas.
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