View Full Version : Write a variable into EEPROM
04-27-2007, 03:12 PM
I’m trying the write a variable into the EEPROM of a BS2.
This is what I try to do:
WRITE 100, "Test"
This is how:
TxT VAR Word
TxT = "Test"
WRITE 100, TxT
This doesn’t work so if anyone could help it would be appreciated?
04-27-2007, 09:33 PM
Sadly, the "STR" modifier only operates in SEROUT (I think).
So, there's the brute force approach:
Txt(4) VAR BYTE ' Declare a byte array
FOR I = 0 TO 3
LOOKUP I, ["T", "e", "s", "t"], Txt(I)
WRITE I, Txt(I) ' Write it to eeprom
Now, if you KNOW what your string is, there's a much more direct approach:
MyText1 DATA "Test", 0
And a more 'complete', general purpose set of library code is attached.
05-01-2007, 03:02 PM
Maybe I need to explain a little bit more. I want to check the battery and display the status (voltage) on a LCD. I found a very usefull and properly working code at: http://www.emesystems.com/BS2rct.htm
The variable Vx must be displayed as text and need to be placed between quotes. Otherwise intead of the value, the corresonding character will be displayed.
The subroutine will read the EEPROM at 100 and will write it the the LCD (44780)
Vx = 18150 / rct + -63
DEBUG HOME,DEC? rct,"Vx=",DEC Vx/10,".",DEC1 Vx
WRITE 100, Vx
There are no "strings" on the Stamp, only Words (2 characters) and Bytes (1 character). To print a stored "string" or the like to a display, you need to do kind of the opposite of what allanlane5 suggested for writing the string. This is *very* common in Stamp applications -- needing to output strings of charactes to a display, speech module, whatever.
Here is a super-simple example
EEaddr VAR Word
i VAR Nib
Char VAR Byte
String1 DATA "text", 0
EEaddr = String1
READ EEaddr, Char
IF Char <> 0 THEN
EEaddr = EEaddr + 1
When the going gets weird, the weird turn pro. -- HST
05-01-2007, 08:58 PM
I'm assuming you're checking the battery voltage pretty often. You should know the eeprom only allows 1 million writes to a location before that location won't work anymore.
So, your "WRITE 100, Vx" is going to wear out location 100 on the eeprom.
If you WANT to write a WORD value, you can do
WRITE 0, WORD Vx
or WRITE 0, Vx.LowByte
WRITE 1, Vx.HighByte
You keep talking about "writing to an LCD", then you wind up "Writing to an EEPROM". Since the EEPROM is not connected to the LCD, I don't know what you hope to achieve by writing to the eeprom.
05-01-2007, 09:01 PM
And you don't say how you're going to 'write to the LCD' yet. Is it a serial interfaced LCD? Are you using a parallel interface?
There's ways to do what you're talking about, once we're certain what you're talking about.
05-01-2007, 09:23 PM
What I meant was that the subroutine "BattChck" writes the battery voltage to EEPROM and that the subroutine "LCDwrmain" reads the eeprom and writes it to the LCD.
Anyway, maybe writing to the eeprom isn't a good idea as you pointed out. I also want to display other things to the LCD so there will be a lot of writing to the eeprom.
Maybe anybody knows how to simply write to a LCD (44780) without using the eeprom? I've attached the eeprom version of the program for Controlling a LCD , which I used (copied from http://www.weethet.nl/english/basicstamp2_lcdcontrol.php#example1)
05-01-2007, 10:57 PM
You need to add the following:
TempStr VAR BYTE(4)
TempVal VAR WORD
I VAR NIB
FOR I = 0 TO 3
TempStr(I) = (TempVal // 10) + $30·· ' "$30" is ascii value of 'zero'
TempVal = TempVal / 10
char = Quote
FOR I = 3 TO 0
char = TempStr(I)
char = Quote
Converting a 'value' stored in memory to a string version of itself is one of those classic early computer science tasks. The pseudocode for this is:
Get the number into "TempVal"
WHILE TempVal is not zero, DO
The least significant character "Char" is "TempVal" MOD by 10.
Add the ascii value for "0" to "Char" to get the ascii value for the number "Char" represents.
Divide TempVal by 10.
05-02-2007, 08:52 PM
The only thing I need to do is to figure out how to add your code and test... hope I'll have some time this evening :)
05-04-2007, 08:13 PM
allanlane5, I'm struggling with adding your code and could use some help?
05-04-2007, 10:53 PM
Sure. Upload what you've got so far, and I'll see what I could do.
05-04-2007, 11:02 PM
This is what I've got so far, as you can see donno where to add your piece..
05-04-2007, 11:08 PM
Now, we talked about this. If you keep writing that value to the eeprom, you're going to wear the little bugger out. Just assign a variable for the value.
Otherwise -- what's not working?
In other words, what exactly IS the string that needs to be sent to the LCD?· Does it have leading and trailing quotes?· Is it JUST the Ascii characters of the value?
05-05-2007, 04:35 AM
I want to have the value of "vx" send to the LCD as ascii characters and without the use of the eeprom. For exampe if vx = 520 I want to have 520 displayed on the LCD.
Sorry that I wasn't clear enough...hope I'm now?