Re: [ts-7000] Problem write on rs-485 TS7800

[Mika Westerberg <>]

On Wed, May 19, 2010 at 08:20:55AM -0000, rodriguezromain62 wrote:
> Hello all, I have a problem with the function write(fd,data,sizeof(data));
> 
> I use a rs-485 to get value of a PT100 temperature sensor.
> I put a 0 to bit 15 on register 0xE800000C to get rs-485 ON
> the PT100 needs a command to return temperature, so I need to send some char, 
> like "TAI".
> 
> I try this : fprintf(stderr,"%c",write(fd, 'T', 1));
>              fprintf(stderr,"%c",write(fd, 'A', 1));
>              fprintf(stderr,"%c",write(fd, 'I', 1));

If you are using standard write(2) syscall, above does bad things. See:

        ssize_t write(int fd, const void *buf, size_t count);

second parameter is pointer to buffer, you are writing numeric value of char 
there.

And also write does return number of bytes written (or -1 on case of error).

Regards,
MW


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