String & WRITE

[Ron Marcus]

Hello everybody.
Pls. I need yr. help.
With HSerin I read a string coming from a serial port and I get this
string "34567890".
Now I'd like to store (with WRITE) into onchip eeprom starting
from location 0 this string, after that the eeprom memory should look
like this:
34 56 78 90 FF FF FF FF ...............

Are the numbers coming in as 34,56,78..... or are they coming in individually?

[Ron Marcus]

To pack single hex digits into a hex byte, just shift the first digit left four times, then add it to the second digit.

Ron

[BigWumpus]

OK, I just try to make the situation clear...

You receive 8 ASCII-Characters "3", "4", "5", "6", ....
Then you want to pack 2 digits in 1 Byte and write them to the eeprom.

Yust try:
Chars Var byte[8] ;here are the 8 digits
For I=0 to 3 ;generate 4 bytes
;cut off unused bits and pack 2 of them
Dummy=(Chars[I<<1]<<4)|(Chars[(I<<1)+1] & $F)
Write I,Dummy
next I

(Very quick and quite dirty!)

[Darrel Taylor]

Hi BigWumpus,

I know you did it real quick, but I think something's missing.

Dummy=((Chars[I<<1]-"0")<<4)|((Chars[(I<<1)+1]-"0") & $F)

Darrel

[Lotondo]

Thanks for answering, I believe you got me the solution.
I'll try and in case I'm not getting the correct result I'll
come back to you.
Regards
Lotondo

[BigWumpus]

Hi Darrel,

I dont subtract the $30 because
-while shifting it 4 bits to the left, they drop out of the PIC ;-)
-while & $F they where masked out ;-)

try it smart !

[Darrel Taylor]

BigWumpus,

Oh yeah. Your right!

That'll change the way I convert ascii numbers in the future. Thanks.
<br>

[Andrew]

Although the topic is quite old I am interested to solve a similar problem for which will really appreciate your support / expertise.

On short, I am receiving serially 16 ASCII-Characters, say "3", "B", "5", "A", "7", "F","1", "D", "2", "2", "4", "F","E", "E", "A", "6".

Then I need to pack 2 digits in 1 Byte and write them to the EEPROM. The final result should be: 2B 5A 7F 1D 22 4F EE A6.
Any clue or tip with regard to algorithm or conversion formula will be highly appreciated. Have a happy and prosperous New Year !