[PATCH 14/22] staging: comedi: adv_pci1710: support external analog output reference

Ian Abbott abbotti at mev.co.uk
Thu Nov 5 12:42:37 UTC 2015


On 04/11/15 16:55, H Hartley Sweeten wrote:
> The analog outputs can use an external reference to create the D/A output
> range. Add an entry to the comedi_lrange table for it and modify the
> (*insn_write) to support it.
>
> Signed-off-by: H Hartley Sweeten <hsweeten at visionengravers.com>
> Cc: Ian Abbott <abbotti at mev.co.uk>
> Cc: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
> ---
>   drivers/staging/comedi/drivers/adv_pci1710.c | 13 ++++++++-----
>   1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/staging/comedi/drivers/adv_pci1710.c b/drivers/staging/comedi/drivers/adv_pci1710.c
> index 86ed288..339130b 100644
> --- a/drivers/staging/comedi/drivers/adv_pci1710.c
> +++ b/drivers/staging/comedi/drivers/adv_pci1710.c
> @@ -65,6 +65,8 @@
>   #define PCI171X_CLRFIFO_REG	0x09	/* W:   clear FIFO */
>   #define PCI171X_DA_REG(x)	(0x0a + ((x) * 2)) /* W:   D/A register */
>   #define PCI171X_DAREF_REG	0x0e	/* W:   D/A reference control */
> +#define PCI171X_DAREF(c, r)	(((r) & 0x3) << ((c) * 2))
> +#define PCI171X_DAREF_MASK(c)	PCI171X_DAREF((c), 0x3)
>   #define PCI171X_DI_REG		0x10	/* R:   digital inputs */
>   #define PCI171X_DO_REG		0x10	/* W:   digital outputs */
>   #define PCI171X_TIMER_BASE	0x18	/* R/W: 8254 timer */
> @@ -111,9 +113,10 @@ static const struct comedi_lrange pci1711_ai_range = {
>   };
>
>   static const struct comedi_lrange pci171x_ao_range = {
> -	2, {
> -		UNI_RANGE(5),
> -		UNI_RANGE(10)
> +	3, {
> +		UNI_RANGE(5),		/* internal -5V ref */
> +		UNI_RANGE(10),		/* internal -10V ref */
> +		RANGE_ext(0, 1)		/* external Vref (+/-10V max) */

Minor niggle:

The comment for the external Vref is slightly confusing.  The manual I 
have says:

By inputting an external reference voltage: -xV , where |x| <= 10,
you will get a output voltage range: 0 to xV.

So the external reference voltage is never positive.  How about this?:

	/* external -xV ref, |x| <= 10 */

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti at mev.co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-


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