[hpsdr] Revised USB Protocol document

[John Marvin]

  From my perspective this document is written primarily for software 
developers.  They might not read the schematics and realize that the 
preamp setting and the Hermes attenuator setting both wind up 
controlling the same device.  If they were to develop software using 
this spec they might offer both options when they probably should offer 
just one (The current version of PowerSDR that was modified for this 
feature lets you choose whether to enable the Hermes attenuator and when 
you do it  replaces the fixed -20 db attenuator).  If they offered both 
and they set the Hermes attenuator to -10  they might not understand why 
when they change the preamp setting that the signal level would only 
change by 10 db rather than 20 db.

So in my opinion they interact, although it appears that the solution 
chosen for implementation was the best possible choice, i.e. last 
control takes effect, regardless which one it is, since that preserves 
backward compatibility and make the most sense.

I just thought for those who aren't acquainted with all the internals 
there should be something that lets people know that these two 
independent C&C settings wind up changing the same device.

I'm not trying to start an argument, I'm just explaining my perspective 
as a software developer.

John
AC0ZG

On 11/16/2012 4:10 AM, Phil Harman wrote:
> Hi John,
>
> There is no interaction and you can use either method.
>
> 73 Phil...VK6APH
>
> -----Original Message----- From: John Marvin
> Sent: Friday, November 16, 2012 2:49 AM
> To: hpsdr at lists.openhpsdr.org
> Subject: Re: [hpsdr] Revised USB Protocol document
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> I believe on Hermes "preamp off" maps to setting the Hermes attenuator
> to -20 db. Should there be some text in this document explaining how the
> preamp on/off setting will interact with the higher granularity ability
> to set the attenuator that was just added?
>
> Thanks,
>
> John
> AC0ZG
>
> On 11/15/2012 4:42 AM, Phil Harman wrote:
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> All,
>>
>> There is an updated USB Protocol document (V1.44) available here:
>>
>> http://svn.tapr.org/repos_sdr_hpsdr/trunk/Documentation
>>
>> This adds support for the 0-31 dB attenuator on Hermes.
>>
>> 73 Phil....VK6APH
>>
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