On Thursday, October 08, 2015 3:03 AM, Ian Abbott wrote:
> On 07/10/15 19:09, H Hartley Sweeten wrote:
>> According the the PCI-2006M user's manual, bipolar ranges use 2's
>> complement coding and unipolar ranges are straight binary. Fix
>> ii20k_ao_insn_write() to use the correct coding based on the range.
>>
>> For aesthetics, use the comedi_offset_munge() helper to handle the
>> munging of the data.
>>
>> Signed-off-by: H Hartley Sweeten <hsweeten@xxxxxxxxxxxxxxxxxxx>
>> Cc: Ian Abbott <abbotti@xxxxxxxxx>
>> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/staging/comedi/drivers/ii_pci20kc.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/staging/comedi/drivers/ii_pci20kc.c b/drivers/staging/comedi/drivers/ii_pci20kc.c
>> index 4d3f89c..6e2ce93 100644
>> --- a/drivers/staging/comedi/drivers/ii_pci20kc.c
>> +++ b/drivers/staging/comedi/drivers/ii_pci20kc.c
>> @@ -146,6 +146,7 @@ static int ii20k_ao_insn_write(struct comedi_device *dev,
>> {
>> void __iomem *iobase = ii20k_module_iobase(dev, s);
>> unsigned int chan = CR_CHAN(insn->chanspec);
>> + unsigned int range = CR_RANGE(insn->chanspec);
>> int i;
>>
>> for (i = 0; i < insn->n; i++) {
>> @@ -153,9 +154,9 @@ static int ii20k_ao_insn_write(struct comedi_device *dev,
>>
>> s->readback[chan] = val;
>>
>> - /* munge data */
>> - val += ((s->maxdata + 1) >> 1);
>> - val &= s->maxdata;
>> + /* munge the offset binary to 2's complement if needed */
>> + if (comedi_range_is_bipolar(s, range))
>> + val = comedi_offset_munge(s, val);
>>
>> writeb(val & 0xff, iobase + II20K_AO_LSB_REG(chan));
>> writeb((val >> 8) & 0xff, iobase + II20K_AO_MSB_REG(chan));
>>
>
> I'm not sure about that as there are discrepancies in the manual. The
> one I found was at:
>
> https://www.uni-due.de/~hp0259/agwiki/lib/exe/fetch.php?media=anleitungen:pci-20006m.pdf
I have the same manual.
> In "5. Specifications" it has:
>
> CODE
> UNIPOLAR Binary
> BIPOLAR Complementary Binary
>
I saw this part.
> But then under "D/A Codes" it has:
>
> OUTDATA Volts Unipolar Volts Bipolar
> ------- -------------- -------------
> 32767 +Full Scale -1 LSB *
> 0 +½ Full Scale 0
> -1 +½ F.S. - 1 LSB -1 LSB
> -32768 0 -Full Scale
>
> ± 5V Range: OUTDATA = VOLTS * (65536 / 10)
> ± 10V Range: OUTDATA = VOLTS * (65536 / 20)
> 0 to 10V Range: OUTDATA = (VOLTS * (65536 / 10)) - 32768
Missed this part...
> * I think that's a typo and should be "+Full Scale - 1 LSB".
>
> The table (with typo corrected) and formulae indicate that for both
> unipolar and bipolar, -32768 is the lowest voltage and +32767 is the
> highest voltage, so we should munge comedi sample values regardless of
> range.
Looks like you are probably correct.
I'll fix the patch and repost the series. Thanks.
Hartley
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