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'[PIC]: Slave PIC on 877 was [PIC:] Not about Ol'
2004\02\17@175223 by Jim Franklin

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Dwayne said:

>Your approach seems quite reasonable and is similar to what I do on a
>regular basis.

I like it when someone agrees with my concept, it may not be a new concept
or anything cutting-edge, but it gives one the feel-good factor to want to
carry on.

>Make sure that you have a way of setting the display cursor
>position - I don't see anything in your list above for doing this.

The list has grown and changed a bit in the last day or so,
On start-up the Slave reads the internal eeprom and displays the message
stored from location 0x00 up to 0x13 (20 chars) on the LCD - "Welcome
message" style
Mxxyy      - Move cursor to Line xx, Column yy
Wxxyy      - Write yy to eeprom location yy
Rxx        - read from eeprom location xx and send on serial to master.
D<string>  - Display string of up to 20 chars at current LCD location.
X          - Clear display and set cursor to 1,1
Z150163    - Wipe header (eeprom locn 0x00) and restart slave
i<string>  - Write the string to eeprom from location 0x00 and terminate
with 0x00
            This is the welcome message.
It currently takes 899 words of ROM and 49 words of RAM, (a fair chunk of
this is the LCD/Serial library stuff) so I have some room to play.


>One thing to consider: text strings can eat a lot of program space -
>storing them on the slave micro that also drives the display is a great way
>to simplify the master.  Just call them up by number.  In other words, add
>another function to your command language where you simply specify the
>message id.  That message is then displayed from text strings stored (hard
>coded) on the slave.  Note that you should still be able to compose and
>send messages from the master to the display.

I like the idea of the numbered messages, I can feel a command 'N' coming
on. :)

>The version I use on a regular basis assumes that the entire serial string
>is intended for the slave.  The command byte is the first thing in the
>string, followed by any data parameters.  I use either <cr> <lf> *or* an
>idle period of x milliseconds as the string terminator ...

I do it in this format, but the idle timeout period sounds like a good idea.

Thanks Dwayne, some more useful pointers.

Jim

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