[hpsdr] Hermes input attenuator enable bit not documented ?

Phil Harman phil at pharman.org
Mon Jan 21 03:10:05 PST 2013

Hi Andrea,

You are quite correct and apologies for not including this in the protocol 

I've add this to the protocol and  V1.46 is now in SVN.

73 Phil...VK6APH

-----Original Message----- 
From: Andrea Montefusco
Sent: Monday, January 21, 2013 8:06 AM
To: HPSDR list
Subject: [hpsdr] Hermes input attenuator enable bit not documented ?

***** High Performance Software Defined Radio Discussion List *****

Hi all,

maybe it has already been spotted and reported, but it seems to me in 
protocol doc version 1.45 a
bit of information is missing.

During testing I am doing in order to extend  ghpsdr3-alex hpsdr-server 
functionality, I was unable
to activate the Hermes attenuator (I have a TAPR Hermes inside an ANAN-10 
case and PA).

So, browsing the Verilog code (Hermes.v), I discovered that, aside the value 
of attenuation, there
is a additional bit, named Hermes_atten_enable, that is decoded into the 
register 0x14-C4:

if (IF_Rx_ctrl_0[7:1] == 7'b0001_010)
   IF_Line_In_Gain   <= IF_Rx_ctrl_2[4:0];    // decode line-in gain setting
   Hermes_atten      <= IF_Rx_ctrl_4[4:0];    // decode input attenuation 
   Hermes_atten_enable <= IF_Rx_ctrl_4[5];    // decode Hermes attenuator 

looking to the code below, I believe (but may be wrong due my poor knowledge 
of Verilog) that the
attenuation value is kept in account as specified, but only if that enable 
bit is set.
Otherwise the Preamp bit (0x00-C3) wins and the DAT attenuator is fully 
If even Preamp is  zero, the DAT is set to -20 dB.

assign atten_data = Hermes_atten_enable ? Hermes_atten : (Preamp ? 5'b0_0000 
: 5'b1_0100);

Now, whilst all the above could be understood from previous messages in 
list, I think the doc should
be changed accordingly.


Andrea Montefusco iw0hdv        http://www.montefusco.com
tel: +393356992791                     fax: +390623318709
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