Reading serial data

[Labjac]

Hallo

I'm trying to read a serial string and then test is, if it's a cetain value I would like to do something, but I'm not sure where I'm going wrong, Firstly the compiler gives me an error if I try to test c please have a look at the program and let me know where I'm going wrong.

Secondly, I want to read a serial string that's about 20char long, how can I do this, the only option I can see is %c which is a single character.

[E_Blue]

First, in order to receive more than one character or byte you need a buffer.

Second, to avoid loss some bytes don't use delays waiting for the incoming data, the function getc() already do that automatically without the risk of losing bytes.

A better practice is to use an interrupt service routine, so while the processor is waiting for the incoming byte can do another thing like read a button, and you process the data when the data stream is finished.

To know when the stream is finished you can detect /r/n or any character below "space"(0x20).
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Electric Blue

[Ttelmah]

%c, is for _outputting_ a character. Not for reading it.

Learn to use the code buttons for posting here, and indent your code (makes it easier for _everyone_.)...

[SherpaDoug]

If all he is looking for is a singe byte he really doesn't need a buffer or ISR so the code he has should work if he removes the delays. Getc() will wait, possibly forever, for a Start bit, capture the next 8 bits as data and check that the 9th bit is a Stop bit.

Does the printf() statement report the correct character? Is the problem that "2" is a null terminated string and he should use '2' instead? I would try the ASCII code 0x33 in the comparison.

Once you get the single byte to work and you want to move on to 20 character strings you should look at buffers and Interrupt Service Routines. The ISR will read one character at a time into the buffer, usually until a terminator like <CRLF> is seen when it sets a flag. When main() sees the flag set it checks the buffer for the matching string.
_________________
The search for better is endless. Instead simply find very good and get the job done.

[Ttelmah]

However the reason his code fails to compile is the missing brackets (as I said in my earlier post). At least with these he should start forward.

Best Wishes

[Labjac]

Hi

Telmah even the code you gave me failed to compile, not sure if it's something I'm doing wrong, and if it got something to do with my compiler.

do { //This avoids compiler error message from while
Printf("Enter a string:");
//Don't delay - start looking for string ASAP
get_string(cbuffer,24);
Printf("The string is: %s\n\r",cbuffer);
delay_ms(1000);

If (strcmp(cbuffer,look_for,strlen(look_for)==0) (Compile error). {
output_high(Op1);
delay_ms(100);
output_low(Op1);
Printf("Correct \n\r");
}
}
}

I did add the input.c file but the error I get it the following:

\main.c" Line 27(36,42): Expecting a close paren

Background is a bit more toward structured text programming and some VB so yes, still learning new syntax as I go along, but code it more or less the same.

SherpaDoug the previous code did Printf the correct character, but is went throught the loop twice everytime, but as you said I think it got to do with the delay, will remove it from the code and see what happens.

Thanks.

[Ttelmah]

The compiler is telling you exactly what is wrong. I missed the last close parenthesis on the if statement.

Best Wishes

[SherpaDoug]

If printf() is giving the correct character, I think your original problem is that
If c=="2"
compares c to a null terminated string containing 2 and a null. Try comparing to ASCII code 0x33 or I think '2' should also work (single quotes, not double quotes).
_________________
The search for better is endless. Instead simply find very good and get the job done.

[Ttelmah]

The reason it won't compile, is that 'IF', _needs_ brackets.
This has been pointed out already.
The correct syntax, is: