16f687 - Where is the data stored?

[rmteo]

Why not store the messages as constant strings in program (FLASH) memory?

[andywpg]

Why not store the messages as constant strings in program (FLASH) memory?

I had sorta thought about that..........but I've always wondered how you tell what memory is not going to be used for the program. I always make the code non-relocatable when asked, but how do you..........

Wait a minute, do you just read the chip and look at the hex dump to see what spots are left blank after the program is in it? Is it that simple? Then you just pick an area that isn't being used? Am I on the right track?

That's a great idea! It would certainly lower the serial data overhead - from 39 bytes per transmission to 11. I know, not a lot of data either way, but less chance of errors when the receiver is in a race car!

Thanks

[mackrackit]

http://www.picbasic.co.uk/forum/showthread.php?t=137

[HenrikOlsson]

Hi,
Lets say the number of message to be displayed comes in and gets stored in a variable called message.

Select Case Message
   Case 1
      LCDOUT $FE, 1, "This is message 1"
   Case 2
      LCDOUT $FE, 1, "This is message 2"
   Case 3
      LCDOUT $FE, 1, "This is message 3"
   Case Else
      LCDOUT $FE, 1, "Unknown message"
   End Select

Here the strings are stored in program flash (where else should it go?) and written to the LCD when the LCDOUT statement executes. It's not the most efficient way of doing it but it's probably the easiest. If the messages are partly "the same" (like in the above example) you can have subroutines to print just that part which you then GOSUB from within the Case section, that will save on flash since you don't have to store the same string ("This is message") more than one time

Case 1
   GOSUB FirstPart
   LCDOUT $Fe, 1, "1"
...
...
End Select
...

FirstPart:
   LCDOUT $FE, 1, "This is message "
RETURN

/Henrik.

[andywpg]

Hi,
Here the strings are stored in program flash (where else should it go?) and written to the LCD when the LCDOUT statement executes. It's not the most efficient way of doing it but it's probably the easiest. If the messages are partly "the same" (like in the above example) you can have subroutines to print just that part which you then GOSUB from within the Case section, that will save on flash since you don't have to store the same string ("This is message") more than one time[code]
/Henrik.

Love the idea, unfortunately, the messages are ALL different. Some have similar parts, but not similar enough to make that viable.

That's the reason for LOTS of messages.

I decided to store 16 characters for each message (including leading and trailing spaces) because it makes displaying them SO much easier. Each one is a complete line on the LCD, and the loop is the same, no matter if the message is " BLACK FLAG "
or " REPORT TO PIT ". I want each message centered in the display for ease of reading at race speeds.

Ciao!

Andy

[rmteo]

Storing spaces is extremely inefficient. Create a routine that pads the message with the appropriate number of leading/trailing spaces before sending it out to the LCD.

[andywpg]

Storing spaces is extremely inefficient. Create a routine that pads the message with the appropriate number of leading/trailing spaces before sending it out to the LCD.

I suppose I could store each message without spaces, then write a unique "stop character".

Then I could just count the characters to the stop character, then calculate the number of spaces needed to pad it to the center of a 16 character line.

The only thing is accessing the right message. I intended to send the message number as part of the data block. I was going to calculate the start address of the message from the message number, and retrieve 16 characters. I guess I could just send the start address as the message number, then retrieve characters until I encounter the stop character. That would work, and is WAY more efficient (in both memory space and processor cycles).

Thanks!

[HenrikOlsson]

Why not clear the screen, move the cursor to the first position, print the message?

CursorPos VAR BYTE          ' 0=first line first char, 64=second line first char (I think, usally...)

CursorPos = 1
GOSUB Clear_and_set_cursor
LCDOUT "Report to pit"

Pause 2000

CursorPos = 5
GOSUB Clear_and_set_cursor
LCDOUT "STOP"

' and so on

END

Clear_and_set_cursor:
   LCDOUT $FE, 1, $FE, ($80 + cursorposition)
   RETURN

/Henrik.

[Charlie]

Storing spaces is extremely inefficient. Create a routine that pads the message with the appropriate number of leading/trailing spaces before sending it out to the LCD.

Of course, shipping product with unused memory is pretty inefficient too. If there's plenty of unused program store, why waste time improving efficiency, particularly for a code block that isn't very reusable?
To paraphrase old movies, "smoke 'em if you've got 'em, lads." But if things are tight, I agree completely.