ASCII characters to decimal number

R

russbow

Senior Member
I need to convert an ascii string received by serin to a decimal number.
This code works in the simulator.

Code: 
#picaxe18m2

'Set up artificial string

eeprom 0,("1234")

do

read 0,b0,b1,b2,b3	'Read back ASCII values


 sertxd (b0,b1,b2,b3,cr,lf)
 
 pause 1000
 
 'Convert ASCii to decimal
 
 for bptr =0 to 3
 
 @bptr=@bptr-48
 
 next bptr
 
 sertxd ("Decimal ",#b0," ",#b1," ",#b2," ",#b3,cr,lf)
 
 pause 2000
 
 'Scale place values
 
 w2=b0*1000
 w3=b1*100:w2=w2+w3
 w3=b2*10:w2=w2+w3
 w3=b3:w2=w2+w3
 
 sertxd ("W2 = ",#w2,cr,lf)

 
 
 pause 2000
 
 loop
Although I get expected results, is there a better way to do it. Can you see any pitfalls

Thanks,

R.
 
W

westaust55

Moderator
you indicate you have EEPOM data as an artificial string.

Where will the final data be coming from?

DO you need SERIN pin, baud, #w3 ; to receive an ASCII string of up to 5 digits and automatically strips the ASCII encoding to put the value into a word variable
or SERRXD #w3 ; possible if coming from the PC
 
hippy

hippy

Ex-Staff (retired)
w2=b0*1000
w3=b1*100:w2=w2+w3
w3=b2*10:w2=w2+w3
w3=b3:w2=w2+w3

Can become a more simpler ...

w2 = b0 * 10 + b1 * 10 + b2 * 10 + b3

PICAXE maths is strictly left to right, no operator precedence, hence why all are * 10.
 
R

russbow

Senior Member
@Nick. Thanks but I need to combine 4 characters to a number.

@ Westy
DO you need SERIN pin, baud, #w3 ; to receive an ASCII string of up to 5 digits and automatically strips the ASCII encoding to put the value into a word variable
or SERRXD #w3 ; possible if coming from the PC
Click to expand...
Sort of. Ascii string sent via RF link to base 18m2. Working fine as is, and all displays ok. Have a thought might want to log min / max values received. Hence requirement to convert to decimal.

@Hippy
w2 = b0 * 10 + b1 * 10 + b2 * 10 + b3
Click to expand...
As ever, spot on. I tried
Code: 
 w2=b0*1000+b1*100+b2*10+b3
and of course got the wrong answer. Need to get a bit of paper and do the 10*10*10 bit.

Thanks to you all.
 
A

Armp

Senior Member
If you don't need the individual digits

Code: 
#picaxe18m2

'Set up artificial string

eeprom 0,("1234")

read 0,b0,b1,b2,b3	'Read back ASCII values
 
bptr =0 
 
w2 = @bptrinc * 10 +@bptrinc * 10 +@bptrinc * 10 +@bptrinc - 53328
 
Last edited:
R

russbow

Senior Member
Why is it so obvious when shown the right way, even though it looks 'wrong'

Code: 
w2 = b0 * 10 + b1 * 10 + b2 * 10 + b3
So the progression is 1 > 10 > 12 > 120 > 123 > 1230 > 1234

@Armp. Havn't tried your code yet. Why the - 53328 at the end? Something to do with stripping back the ascii values ??
 
A

Armp

Senior Member
Yup - its 48 + 480 +4800 + 48000....
The code snippet above will run in PE - try it.

I store directly from serin into RAM, then just point bptr to the beginning of the buffer - no variables required.

Code: 
Bptr = $40
serin inpin, baud, @bptrinc, @bptrinc, @bptrinc, @bptrinc
Bptr = $40
w2 = @bptrinc * 10 +@bptrinc * 10 +@bptrinc * 10 +@bptrinc - 53328
 
R

russbow

Senior Member
Like it !! Although you say ' ... no variables required ... ' they are of course used and retrievable as b0 etc.

I guess this is only good for a max of four ascii characters.

Yup - its 48 + 480 +4800 + 48000....
Click to expand...
Thanks for the tips

R.
 
A

Armp

Senior Member
russbow said:
Like it !! Although you say ' ... no variables required ... ' they are of course used and retrievable as b0 etc.
Click to expand...
Nope! I set Bptr=$40 so the characters are stored in the RAM area, not the 'variable' area.
Leave it at 0 if you WANT to use b0...

I guess this is only good for a max of four ascii characters.
Click to expand...
How many digits did you want?
 
W

westaust55

Moderator
russbow said:
@ Westy

Sort of. Ascii string sent via RF link to base 18m2. Working fine as is, and all displays ok. Have a thought might want to log min / max values received. Hence requirement to convert to decimal.

Thanks to you all.
Click to expand...
What do you mean by "sort of"?
If you have a number up to 5 digits coming in ASCII encoded and followed by say "cr" or other non "0" to "9" then
SERIN with #w2
Accepts the string and auto strips ASCII leaving you with the basic decimal number.
So no need to save individual ASCII characters and recombine.
Or am I missing something?
 
R

russbow

Senior Member
@Westy. Sorry, you are not missing anything, my bad choice of wording and my usual unclear explanation.
Yes, I receive four ascii characters via an RF serin, and I want to combine them to a decimal.

Thus - "1", "2", "3", "4" to equal 1234. The code was just a routine to try my ideas. As usual came a cropper on the integer maths but got it working. Now fully understand the ways suggested.

The string I require is the 4th to 7th character, so I serin b0,b0,b0,b0,b1........

Hope that makes it clearer
 
W

westaust55

Moderator
Ah yes, thanks, that clears up the situation.
You are parsing a data string and extracting 4 characters from that string.
As a result the #w2 for SERIN would/may not work even if you skip the first 4 characters unless you know the next character is always a non "0" to "9" to terminate the SERIN accepting dfata for word variable w2.
 
A

Armp

Senior Member
russbow said:
The string I require is the 4th to 7th character, so I serin b0,b0,b0,b0,b1........
Click to expand...
I try not to use variables for temp storage....

Code: 
Bptr = $40
serin inpin, baud, @bptr, @bptr, @bptr, @bptrinc, @bptrinc, @bptrinc, @bptrinc
Bptr = $40
w2 = @bptrinc * 10 + @bptrinc * 10 + @bptrinc * 10 + @bptrinc - 53328
 
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