comedi_da.c

linux驱动开发comedi的一些例子

/* Digital to Analog: This is the COMEDI_DA.c file       */
/* Creates and interface for using COMEDI Device Drivers */

/* This file is from RTiC_Lab. The standard include file for device drivers */
#include "main.h"
/* This two include files are from COMEDI */
#include "comedi_module.h"
#include "comedi.h"

/*************************************************/
/* 
   I need to include a header file called "device_config.h" to 
   configure the devices 
*/
/* #include "device_config.h" */
/*************************************************/

/* Three functions have to be implemented. They are:
 * int RTiC_init_DA_card(void);
 * void RTiC_DA_run(void);
 * int RTiC_stop_DA_card(void);                          */

/* There are few things that have to be planned before using COMEDI and
   RTiC_lab together. For COMEDI the user has to device the minor number for
   the device. She does it when "comedi_config /dev/comediX" is called. 
*/

/* COMEDI uses three structures when it calls the trig[0] functions. The
   prototype for this call is:
   int trig[0](comedi_device *,comedi_subdevice *,comedi_trig *)
   We need the following structures:
*/
static comedi_device    *cd;
static comedi_subdevice *cs;
static comedi_trig      *ct;

/* We need an data value for COMEDI ...*/
static sampl_t comedi_data;
/* ... and an unsigned int to tell COMEDI what channel to write to and how */
static unsigned int comedi_channel;

/*******************************************************************************/
/* NOTE: This three next values can be change by the user to fit his/her needs */

/* The range for the analog to digital convertions     */
/* Read the file from COMEDI:             */
#ifndef COMEDI_RTIC_RANGE 
#define COMEDI_RTIC_RANGE 8
#endif
/* The reference for the analog to digital convertions */
#ifndef COMEDI_RTIC_AREF
#define COMEDI_RTIC_AREF  AREF_GROUND
#endif
/* According with the X value in "comedi_config /dev/comediX" */
#ifndef RTiC_COMEDI_MINOR_DAC
#define RTiC_COMEDI_MINOR_DAC 0
#endif
/*******************************************************************************/

/* This function is called at initialization by RTiC_lab */
int RTiC_init_DA_card(void)
{
  int i=0;
  int right_subdevice = 0;

  printk("In initialization \n");

  /* Get comedi_device structure according with RTiC_COMEDI_MINOR_ADC */
  cd = comedi_get_device_by_minor(RTiC_COMEDI_MINOR_DAC);
  
  /* Allocate memory for the structure needed by COMEDI */  
  ct = (comedi_trig*) (kmalloc(sizeof(comedi_trig), GFP_KERNEL));
  if(ct == NULL)
    return -ENOMEM;
  memset(ct,0,sizeof(comedi_trig));

  /*  int n_subdevices;
      comedi_subdevice *subdevices; */
  /* Look up for the subdevice "COMEDI_SUBD_AI": Analog Input 
     by the end of this loop, cs will point to the apropriate subdevice */
  for (i=0; i < cd->n_subdevices && (right_subdevice == 0); i++){

    cs = cd->subdevices+i; /* Isn't it the same subdevices[i] than subdevices+i? */

    if (cs->type == COMEDI_SUBD_AO)
      right_subdevice = 1;
  }
  
  if (right_subdevice != 1)
    return(-1); /* The device is not there. Maybe return ENXIO 6
		   No such device or address                     */
  
  /* Check that the value of NUM_CONTROL_INPUTS do not exceed the number of 
     available ADC channels                                                 */
  if (NUM_CONTROL_OUTPUTS > cs->n_chan)
    return (-1);

  ct->data = &comedi_data;
  ct->n_chan = 1;

  return 0;
}

/* This function is called from RTiC_Lab code every period */
void RTiC_DA_run(void)
{
  int index;
  /* In this function I have to write to the DACs from 0 to 
     NUM_CONTROL_OUTPUTS, the values are from RTiC_control array  */
  
  /* Write to all the NUM_CONTROL_OUTPUTS channels */
  
  for (index=0; index<NUM_CONTROL_OUTPUTS; index++)
    {           
      /* How should COMEDI write to the channels  */      
      comedi_channel = CR_PACK(index,COMEDI_RTIC_RANGE,COMEDI_RTIC_AREF );
      ct->chanlist = &comedi_channel;
      comedi_data = (sampl_t) ( (*(RTiC_control+index)) * 400);
      ct->data = &comedi_data;
      cs->trig[0](cd, cs, ct);      
      /* printk("[%d]->%X ", index, ct->data[0]);*/
    }  
  
  printk("\n");
}

/* This function is called at the end from RTiC_lab */
int RTiC_stop_DA_card(void)
{

  printk("In stop card \n");
  /* Free the memory for comedi_trig_struct */
  kfree(ct);
  /* The memory for comedi_device_struct is free by COMEDI */

  return 0;
}

void RTiC_reset_DA(void)
{

}