I2C write - value too big

[ruijc]

Hi all,

i have found a bug in my temperature logger (16F88 + 24LC512+LM35).
I works pretty well until it reaches temp values of 124ºC, for values above it are displayed as 0ºC or 0,5ºC.

I've looked at my code and i think a know what the problem is: I need to separate the variable into lowbyte and highbyte.

The problem is that i'm not being able to get this working that way. Here's why :


This way does not work:

I2CWRITE SDA,SCL,CTW,ADDR,[tempe.highbyte]
pause 10
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR,[tempe.lowbyte]

This way does not work:

I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[tempe.highbyte]
pause 10    
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[tempe.LOWBYTE]

Only this way one works:

I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[tempe]
pause 10    
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[tempe]

Long story short:
I can make it work with the eeprom BUT only with Address high and low. If i try to separate the variable tempe into high and low it doesnt work

Any ideas ?
Thanks
.

[JD123]

Use a word size variable. PBP will read the two bytes. Check PBP manual for the loading order. You may have to flip .highbyte and .lowbyte outside the I2CREAD statement.

[ruijc]

Thanks for the help JD123,

The variable is already a word sized.

You may have to flip .highbyte and .lowbyte outside the I2CREAD statement

Outside ? How is this done ?

.

[ruijc]

checked the PBP manual and did some changes to the code but did not worked ( not sure this is what you mean ):

what i did:

Added alias

tempe   var  word

temp1   var tempe.highbyte
temp2   var tempe.lowbyte

saving data to eeprom

I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[temp1]
pause 10    
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[temp2]

.

[JD123]

checked the PBP manual and did some changes to the code but did not worked ( not sure this is what you mean ):

what i did:

Added alias

tempe   var  word

temp1   var tempe.highbyte
temp2   var tempe.lowbyte

saving data to eeprom

I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[temp1]
pause 10    
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[temp2]

.

Just use:

I2CWRITE SDA,SCL,CTW,ADDR,[TEMP]

In both ADDR and TEMP they are word size and PBP will send each byte out for the word - no need to bust them up and send them individually.

[ruijc]

Just use:
I2CWRITE SDA,SCL,CTW,ADDR,[TEMP]

This was my first option, but for some reason the eeprom does not store the data this way.

Actually, with the 12F675 chip this eeprom works well with :

I2CWRITE SDA,SCL,CTW,ADDR,[temp.highbyte]
pause 10
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR,[temp.lowbyte]

But not with the 16F88.

I got it working with :

I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[tempe]
pause 10    
ADDR=ADDR+1
I2CWRITE SDA,SCL,CTW,ADDR.highbyte,addr.lowbyte,[tempe]

The problem now is for the lenght of the tempe value when over 125ºC

.

[JD123]

Just the use of a word size variable, invokes PBP to read two bytes. It places the first byte in the var.highbyte and the second in the var.lowbyte. EDIT: Sorry, I didn't see that you were not writing, not reading - this is for reading)

If this is not the order you want, you'll have to exchange the two bytes outside the I2C instruction. I'm not sure of all the techniques (like using PBP SWAP) will work, but it's a standard process that can be done using a temporary 'working' word size variable.

temp.highbyte = var.lowbyte
temp.lowbyte = var.highbyte
var = temp