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kam
Joined: 15 Jul 2005
Posts: 59
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| passing uart stream value as an arg |
 Posted: Thu Aug 09, 2012 10:58 am |
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Hi all,
Hope all is well with ya all!
i was wondering if it is possible to pass uart "stream" type as an arg?
example:
| Code: |
#use rs232(UART1, baud=38400,parity=N,bits=8, STREAM=RS1)
#use rs232(UART2, baud=38400,parity=N,bits=8, STREAM=RS2)
.
.
.
c=getc(RS1); // currently supported
c=getc(RS2); // currently supported
.
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c=kamsGetC(RS1); <--- what would be the function prototype for this?
.
.
char kamsGetC(STREAM rs) <--- what is the type???
{
return getc(rs);
}
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Granted I can do this via an ENUM just fine, I was just wondering if it could be done...
~Kam |
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sseidman
Joined: 14 Mar 2005
Posts: 159
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| Posted: Thu Aug 09, 2012 11:08 am |
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| Can't do it, but you can work around it by putting the uart calls in a case statement, switching on some variable to call with the appropriate stream. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19508
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| Posted: Sun Aug 12, 2012 5:02 am |
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It is also important to perhaps understand 'why'.
The stream name, is not really a variable. It is effectively a 'preprocessor directive', telling the compiler to generate different code. So it may switch between generating code for a software UART, hardware UART, or (as in the example), two different hardware UART's.
So when you call 'fputc', with UART1, code to access the first UART registers is generated, while with UART2, code for the second set of hardware is generated.
Simplest way to switch with a variable, is to just generate you own putc_tostream, and getc_fromstream functions, and have these test a global variable, and call fputc/fgetc, with the required stream name. Setup the global variable, and use these functions instead of the normal ones.
Best Wishes |
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bkamen
Joined: 07 Jan 2004
Posts: 1615
Location: Central Illinois, USA
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| Posted: Sun Aug 12, 2012 9:17 am |
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| Ttelmah wrote: |
Simplest way to switch with a variable, is to just generate you own putc_tostream, and getc_fromstream functions, and have these test a global variable, and call fputc/fgetc, with the required stream name. Setup the global variable, and use these functions instead of the normal ones.
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The selection variable doesn't need to be global, does it?
Can't the user have a fully "self contained" function with both fget's pointing to his 2 different streams returning a local result var?
-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19508
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| Posted: Sun Aug 12, 2012 9:49 am |
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Oh, yes, but in general, if he wants overall 'switching', it is nicer to have his own functions, and use these like the normal ones. So, something like:
| Code: |
int1 second_stream=FALSE;
#define select_stream1() second_stream=FALSE
#define select_stream2() second_stream=TRUE
void putc_to_stream(char chr) {
if (select_stream) fputc(chr,UART2);
else fputc(chr,UART1);
}
char getc_from_stream(void) {
if select_stream return(fgetc(UART2));
return fgetc(UART1);
}
//Then to send/get from stream1
select_stream1();
printf(putc_to_stream,"Message to stream1");
//Then to talk to stream 2
select_stream2();
printf(putc_to_stream(),"Message to stream2");
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Making the variable 'global', means the stream can be switched anywhere, and apply to all code that uses the putc_to_stream, or getc_from_stream functions.
Best Wishes |
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