Re: IIO Drivers

[Lars-Peter Clausen <lars@metafoo.de>]

On 02/27/2013 08:50 PM, Chris Micali wrote:
> Last question :)  I'd like to sample from this device as quickly as possible - so I'm assuming I need to trigger quickly?  Should I use iio-trig-periodic-rtc?  Any hints/instructions on how to use that?  Should the driver supply it's own trigger that uses an hrtimer instead?
> 
> Thanks!
> Chris

Hi,

There is a generic hrtimer based trigger:
https://github.com/lclausen-adi/linux-2.6/commit/a3b5c3f7aafbcac562d6f00a6589b110bd9fb71c

Unfortunately it's not upstream ready yet.

I can be registered via a platform_device

static struct platform_device iio_trigger_hrtimer = {
	.name = "iio-trigger-hrtimer",
	.id = 0,
};

- Lars

> 
> 
> On Wednesday, February 27, 2013 at 2:32 PM, Chris Micali wrote:  
>> Guys,  
>>  
>> Thanks a lot for the help! I finally tracked down issues, it was a combination of a few things:
>>  
>> 1. The .channel had to be 0, not 1 in the driver (scan_index didn't matter)
>> 2. 1 or more scan_elements have to be enabled as you mentioned
>> 2. When echoing into the sysfs files it has to have a space after the number (cat 1 > in_voltage0_en and not cat 1>in_vo…) (duh!)
>> 3. The generic_buffer.c program had a few bugs in it causing crashes. I updated the iio_utils.h to a newer version I found here: https://github.com/analogdevicesinc/iio-oscilloscope and then made a few modifications (the newer iio_utils did not parse a few things right in the channel details like bigendian/littleendian)
>>  
>> So generic_buffer is now correctly sampling (although it crashes after a couple, it's probably another iio_utils issue)
>>  
>> Thanks!!
>>  
>> -chris
>>  
>>  
>> On Wednesday, February 27, 2013 at 1:51 PM, Lars-Peter Clausen wrote:
>>  
>>> On 02/27/2013 07:28 PM, Jonathan Cameron wrote:
>>>> On 02/27/2013 05:36 PM, Chris Micali wrote:
>>>>> lars,  
>>>>>  
>>>>> I was under the impression that flag gets added automatically by iio_triggered_buffer_setup (industrialiio-triggers.c:77) - I actually am now able to enable the scan_element after changing my channel .channel and .scan_index to 0 (trying to match exactly the other drivers.)
>>>  
>>>  
>>> Yea, you are right I missed the iio_triggered_buffer_setup part.
>>>  
>>>> Strange, scan_index should have defaulted to zero and the .channel value shouldn't have mattered
>>>> for buffered reads (just effects naming). Might have caused issues with userspace expecting a channel 0
>>>> though...
>>>  
>>>  
>>>  
>>>  
>>>  
>>> I guess the scan_index had nothing to do with this, but I suggested to set
>>> scan_elements/in_voltage0_en to 1, so this clearly wouldn't have worked with
>>> .channel being 1.
>>>  
>>>>  
>>>>> When i run general_buffer (from the docs dir) with that scan element enabled it can no longer read the trigger (Could not open /trigger/current_trigger Failed to write current_trigger file) - this succeeds if that scan_element is not enabled.  
>>>  
>>>  
>>> You can't change the trigger if the buffer is currently enabled. Make sure that
>>> he buffer is disabled (check the buffer/enable attribute).
>>>  
>>> - Lars
>>> u
>>  
> 
> 
> 
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