Message String Table using Readcode

[mytekcontrols]

I've tested the following code on the PIC18F series (I don't know if it will work on other PIC's).

MsgBaseAddr var word
MsgIdx var byte
Msg_Ctr var byte
Char_Ctr var byte
ascii var byte

'================================================
' Program Start
'================================================
'GetMesg Program Routine retrieves character string from Message Table
'Format: "MsgIdx = X: GoSub GetMesg" (where X = 0 to last message in table)

GetMesg:
'Initialize counters
    Msg_Ctr = 0
    Char_Ctr = 0

'Retrieve Message Table Base Address
asm
    movlw  Low Msg_table
    movff  WREG, _MsgBaseAddr
    movlw  High Msg_table
    movff  WREG, _MsgBaseAddr + 1
endasm

'Locate beginning of message string and adjust base address to match
    While MsgIdx > Msg_Ctr                  ' When we have a match, exit!
    Readcode MsgBaseAddr, ascii             ' Retrieve character and
    MsgBaseAddr = MsgBaseAddr + 1           ' move index to next position. 
    If ascii = 0 Then                       ' If at end-of-message...
        Msg_Ctr = Msg_Ctr + 1               ' Increment to next mesg string and
        If MsgBaseAddr // 2 = 0 Then        ' Determine end-of-string padding.
            MsgBaseAddr = MsgBaseAddr + 2   ' If Even #, pad 2 spaces
        Else
            MsgBaseAddr = MsgBaseAddr + 1   ' If Odd #, pad 1 space
        Endif
    Endif
    Wend

;Retrieve message and send it
GetString:
    Readcode (MsgBaseAddr + Char_Ctr), ascii	' Retrieve character
    If ascii = 0 Then Return			' Leave if end-of-message!

'---- your output code goes here (HSEROUT [ascii], LCDOUT ascii, ect) ----

    Char_Ctr = Char_Ctr + 1			' set pointer to next character
    Goto GetString

'================================================
' Message Table
'================================================

' Each string is terminated with a 0
asm
Msg_table
    DATA "message #0",0
    DATA "message #1",0
    DATA "message #2",0
    DATA "message #3",0
    DATA "message #4",0
    DATA "message #5",0
    DATA "message #6",0
    DATA "message #7",0
    DATA "message #8",0
    DATA "message #9",0
    DATA "message #10",0
endasm

Here is the format to call the above routine, in order to output the individual message strings:

    MsgIdx = 0: GoSub GetMesg
    MsgIdx = 1: GoSub GetMesg
    MsgIdx = 2: GoSub GetMesg

In the section: "---- your output code goes here"
You can do whatever you desire to fullfill your particular needs. For instance; In the following example, we add a carriage return and linefeed at the end of the message string, sending it all out the hardware usart (RS232).

;Retrieve message and send it
GetString:
    Readcode (MsgBaseAddr + Char_Ctr), ascii	' Retrieve character
    If ascii = 0 Then Exit			' Leave if end-of-message!
    HSEROUT [ascii]
    Char_Ctr = Char_Ctr + 1			' set pointer to next character
    Goto GetString
Exit:
    HSEROUT [$0D,$0A]
    Return

Anything is possible, just use your imagination.

Edit: corrected missing variable declaration for ascii

Enjoy,

[NavMicroSystems]

Michael,

apart from the fact that you have missed to declare ascii VAR BYTE

it works just fine on my 18F's

That way I can probably get rid of an external EEPROM I was using for message strings.
(presuming there is codespace left to store the strings)

MANY THANKS!

I'll do some further testing and let you know the results.

[mytekcontrols]

Thanks Ralph,

apart from the fact that you have missed to declare ascii VAR BYTE

I fixed it.

That way I can probably get rid of an external EEPROM I was using for message strings.
(presuming there is codespace left to store the strings)

Depending on how you were doing this before, you might see a tremendous savings (especially true if you were using PBP's Table Lookup function).

I certainly can't take all the credit for the idea, since much of this was made possible by looking at other people's code examples. However I do think my approach is possibly unique, since I have been looking, and looking for a solution like this for quite some time now, and never found anything exactly like it. I would be curious to know what other PICs this will work on, since all I use now-a-days are the 18F series, and have no easy way to confirm this.