Re: Adding MAX1363 to BBB

[Jonathan Cameron <jic23@kernel.org>]

On 31/08/15 17:52, Michael Welling wrote:
> On Mon, Aug 31, 2015 at 05:24:21PM +0100, Jonathan Cameron wrote:
>> On 31/08/15 17:01, Greg Wilson-Lindberg wrote:
>>>  
>>>
>>>> -----Original Message-----
>>>> From: Michael Welling [mailto:mwelling79@gmail.com] On Behalf 
>>>> Of Michael Welling
>>>> Sent: Friday, August 28, 2015 5:32 PM
>>>> To: Greg Wilson-Lindberg
>>>> Cc: linux-iio@vger.kernel.org
>>>> Subject: Re: Adding MAX1363 to BBB
>>>>
>>>> On Fri, Aug 28, 2015 at 04:56:20PM -0700, Greg Wilson-Lindberg wrote:
>>>>>
>>>>> I've got the system running, but I get an invalid argument 
>>>> error on the call to iio_buffer_refill().  I'm basically 
>>>> using the same code as for the tsadc, just added in a fourth 
>>>> channel, and none of the setup calls are returning errors, 
>>>> but the first iio_buffer_refill() call returns an error.  
>>>> I've dumped out the parameter that is being passed to the 
>>>> iio_buffer_refill() call and it is the same as the value that 
>>>> was returned from the iio_device_create_buffer() call.
>>>>>
>>>>> I've looked at the libiio source and I don't see anything 
>>>> obvious that should return invalid argument for the 
>>>> iio_buffer_refill() call.
>>>>>
>>>>
>>>> I believe that you need to register an interrupt for buffered 
>>>> access to work.
>>>>
>>>> Do you have an interrupt connected and registered?
>>>>
>>>
>>> Nope, no interrupt.  So I guess I would need to ask, how would I register the interrupt in the Device Tree?
>> The max1363 (and similar) don't have a dataready interrupt as they
>> are clocked of the actual clock cycles of the i2c transfers.  So
>> they only read on demand.
>>
> 
> Ah, yes. Looking at the datasheet the interrupt is triggered by a window
> comparator not end of sample.
That takes me back. It was one of my first drivers ;)  They monitor
stuff is real pain as it does output normal readings when monitor
is running but only after a whole load of other stuff.  I think I got
lazy and decided not to unwind that but just to make the driver not
read the channels when monitor was enabled.

> 
>>>
>>> Or, alternatively, can I just get individual readings through IIO?
>> Either via sysfs, or by adding a sysfs trigger and poking that.
>> To add a sysfs trigger you'll need to probe the module, then poke
>> a number into the add_trigger attribute to create a trigger which can
>> then be associated with the max1363 (as normal).
>>
>> Then to 'fire' the trigger write to the trigger_now attribute of the
>> relevant trigger.
>>
>> Ideally Daniel will be back soonish with a final version of the
>> high resolution timer trigger that would also work well here.
>> (it's rather tied up with some configfs support which wis
>> trickier!).
> 
> It is probably easiest to sample using sysfs directly.
> 
> This would be same as the last method we tried while trying to
> access to TI ADC and touchscreen simultaneously.
> 
> http://www.spinics.net/lists/linux-iio/msg20577.html
That should work fine.

Jonathan
> 
>>
>> Jonathan
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