Strange serial output

beginners
#1

I am reading serial data coming from a series one xbee in API mode.

The data should read like this:
131 4 210 …and the rest makes sense so I will not bore you with it

OF is reading it as
-125 4 -46 …

why is it trying to make the number out of 256 and not 255?

#2

it shouldn’t be like that, the readBytes method gets an unsigned char array as buffer so it doesn’t allow negative values. Perhaps you are printing them as char?

#3

I was confused too.
I used a for loop to do printf(%i, value[i])
I am very new to C++ does the print a char or unsigned char?
The array is an unsigned char.
If it prints char how do I print the unsigned char? (just to check the data)

#4

try with %u instead of %i

#5

changed it to %u

now -125 came out as 4294967171
and -46 as 4294967250

No idea on that one.
At least -125 made sense to me 255-125 = 131

#6

Running this code:

  
  
	printf("%i\n", (char) 131);  
	printf("%u\n", (char) 131);  
	printf("%i\n", (unsigned char) 131);  
	printf("%u\n", (unsigned char) 131);

I get this:

  
  
-125  
4294967171  
131  
131

So try just try re-casting your data as an unsigned char.

Also, a reference on printf.

Also, 4294967171 = 11111111111111111111111110000011, and 131 = 10000011.