Re: [PATCH RFC v2 8/9] Documentation: ABI: testing: add docs for ad9910 sysfs entries

[David Lechner]

On 4/12/26 9:51 AM, Jonathan Cameron wrote:
> On Mon, 23 Mar 2026 11:36:08 +0000
> Rodrigo Alencar <455.rodrigo.alencar@xxxxxxxxx> wrote:
> 
>> On 26/03/22 05:22PM, Jonathan Cameron wrote:
>>> On Wed, 18 Mar 2026 17:56:08 +0000
>>> Rodrigo Alencar via B4 Relay <devnull+rodrigo.alencar.analog.com@xxxxxxxxxx> wrote:
>>>   
>>>> From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
>>>>
>>>> Add ABI documentation file for the DDS AD9910 with sysfs entries to
>>>> control Parallel Port, Digital Ramp Generator, RAM and OSK parameters.
>>>>
>>>> Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
>>>> ---  
>>
...

>>>   
>>>> +		  - "ramp_down": No-dwell low; the ramp resets to upper
>>>> +		    limit upon reaching the lower limit.
>>>> +		  - "ramp_up": No-dwell high; the ramp resets to lower
>>>> +		    limit upon reaching the upper limit.
>>>> +		  - "bidirectional_continuous": Both no-dwell high and low;
>>>> +		    the ramp continuously sweeps without dwelling.  
>>>
>>> Triangle wave?  bidirectional continuous is a rather confusing term so maybe
>>> we should rethink this one.  
>>
>> Mostly yes, but not only that. Sawtooth can be achieved as well by changing
>> the step sizes, also other weird patterns can be achieved by toggling DRCTL pin.
> 
> Sawtooth is kind of a special triangle wave with one very steep side.
> Wikipedia even has: "It can also be considered the extreme case of an asymmetric triangle wave"
> https://en.wikipedia.org/wiki/Sawtooth_wave
> 
>> This mode is the most useful when one does not have an FPGA and want to save
>> resources on controlling the DRCTL pin. That mode name comes from the datasheet,
>> so I suppose it was fine.
> 
> Let us see if we can get more opinions on this.  Whilst I can see the logic of
> the datasheet naming, it's a bit obscure.
> 
It is the same as ramp_up and ramp_down other than what happens when it hits
the limit? If so, I would call it ramp_up_down.