(unknown charset) Re: Comedi problem: reading analog input

From: (unknown charset) Calin A. Culianu <calin_at_ajvar.org> · Date: Thu, 13 Jun 2002 16:49:25 -0400 (EDT)

On Thu, 13 Jun 2002, [iso-8859-1] ANDRES ESCOBAR wrote:

> Hi all,
>
> I tried to read an analog input channel.
>
>
> The segment of code and the problem are as follows:
>
>
> #include <stdio.h> /* for printf() */
> #include <comedi.h> /* also included by comedilib.h */
> #include <comedilib.h> /* 'cuz we're using comedilib
> */
>
> int subdev = 0;         /* change this to your input
> subdevice */
> int chan = 0;           /* change this to your channel
> */
> int range = 0;          /* more on this later */
> int aref = 0;           /* more on this later */
>
> int main(int argc,char *argv[])
>
> {
>         comedi_t *cf;
>         int chan=0;
>         lsampl_t data;
> 	int maxdata,rangetype;
> 	double volts;
>
>         cf=comedi_open("/dev/comedi0");
>
> 	maxdata=comedi_get_maxdata(cf,subdev,chan);
>
> 	rangetype=comedi_get_rangetype(cf,subdev,chan);
>
>
> comedi_data_read(cf->fd,subdev,chan,range,aref,&data);
>
> 	volts=comedi_to_phys(data,rangetype,range,maxdata);
>
>         printf("%d %g\n",data,volts);
>
>         return 0;
> }
>
>
> the name of the program is secondcomedi.c, and then a
> try to compile:
>
> control:/home# cc secondcomedi.c -lcomedi -o
> secondcomedi
>
> and I obtain:
>
> secondcomedi.c: In function `main':
> secondcomedi.c:25: dereferencing pointer to incomplete
> type
> secondcomedi.c:27: warning: passing arg 2 of
> `comedi_to_phys' makes pointer from integer without a
> cast
> secondcomedi.c:27 too many arguments to function
> `comedi_to phys'

comedi_to_phys() takes a comedi_range * argument, not an int/int pair as
you have.  change the comedi_to_phys() call to:

volts=comedi_to_phys(data,comedi_get_range(cf,subdev,chan,range),maxdata);

>
>
> what is wrong?
>
> Thanks.
>
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>
>
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