George Smart - M1GEO

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Using CW Skimmer with Hermes Lite 2 SDR

Posted: 30 Nov 2020 04:19 PM PST
https://www.george-smart.co.uk/2020/...mes-lite-2-sdr



As I was unable to take part in the CQWW CW Contest 2020 due to Coronavirus
COVID-19 regulations, I decided to experiment with using the wideband SDR
of the Hermes Lite 2 SDR (HL2).








The process appeared to be quite smooth, however upon completion, the CW
Skimmers Skim Server (SkimSrv) would report that the SDR connection had
timed out. This transpired to be the hardware watch dog timer (WDT) timeout
inside the FPGA on the Hermes Lite 2 a precaution to stop the SDR from
being stuck in transmit should the connection to it drop:








The solution was two-fold:




Update the HL2 gateware to a version allowing the WDT to be
adjusted/disabled
Update the SkimSrv DLL plugin to a version using the WDT configuration




Getting the Latest HL2 Gateware




The gateware of the HL2 is a bit like what you may consider as firmware.
Only, firmware is code that runs on a CPU or microcontroller, and gateware
is code that configures the internal connections of an FPGA. This
difference is immaterial here, but it is useful to know.




I started off by finding the latest testing version of the HL2 gateware,
which can be found over on Steve Haynal KF7Os project page for the
Hermes-Lite2, under the gateware\bitfiles folder. It is important to note
that some of the files in these folders are compiled with special features
and are often not recommended for general use. At the time of writing,
testing/20201107_72p5 was the latest version that was recommended for more
general use. Other versions had no transmit (but supported 10 receiveres)
or had different filtering. It is important to find a suitable image for
your requirements.




Once you have read the readme and are happy with the notes supplied with
the version of the bitfile (the actual compiled file the FPGA is sent to
configure itself), then you are ready to go.




I used testing/20201107_72p5/hl2b5up_main/hermeslite.rbf (direct link to
download) which supports up to 4 receivers, but also includes transmit and
is suitable for general use again read the notes that are supplied! They
are important. Other variants include 10 receivers, but no TX you may
prefer the 10-RX variant of the gateware. Whatever you chose, youll need to
rename the hermeslite.rbf file to hl2b5up_main.rbf to allow it to be
flashed by SparkSDR. Quisk doesnt seem to care what the file is called.



Programming the Gateware




To program the gateware there are two options. I opted to use SparkSDR2 by
Alan Hopper M0NNB. The process is easy and SparkSDR2 supports Windows and
Linux. Run SparkSDR, press the discovery button (the rotating arrow on the
left) until your Hermes Lite 2 is discovered, and then right-click and
select firmware. From there, navigate from the downloaded and renamed file
hl2b5up_main.rbf and press program. It should take around a minute.








You are also able to use Quisk by James Ahlstrom N2ADR. From the Config
dialogue, select your radio, and then select Program from RBF file. The
update should not take long.








Once the upload is complete, you should power cycle the Hermes Lite 2 SDR,
and then check in your favourite program that the update was successful. I
checked that the radio still worked, and I could see that the revision
gateware had changed to what I expected: 72p5 and that I did indeed have 4
receivers available.







Installing the recompiled HermesIntf.dll




Originally, the HermesIntf.dll file was provided by Vasiliy Gokoyev K3IT on
the GitHub page HermesIntf. However, this DLL does not take advantage of
the extra WDT options available in the HL2 gateware we just updated. To
make such updates, this required the original DLL supplied by Vasiliy K3IT
to be recompiled, incorporating changes from Steve KF7Os gateware.




I was beaten to doing this by Robin Davies G7VKQ, who kindly shared the
rebuilt DLL file with me on Twitter (thanks!!). This DLL file can be
downloaded he HermesIntf_G7VKQ.zip This file is then to be copied into
the SkimSrv folder, typically located within C:\Program Files
(x86)\Afreet\SkimSrv\ on a modern 64-bit version of Windows. You will of
course need to install SkimSrv by Afreet Software from here. A trial
version is available youll need the Skim Server, not the standard CW
Skimmer.








Once youve copied the DLL into the installation folder, you are ready to
fire-up the SkimSrv. SkimSrv has a little icon in the system tray, as shown
below. Click on this to open the SkimSrv settings dialogue.












From here, you can use the Skimmer tab to set up the frequencies, sample
rates, radios, etc., to use. This is all as you would expect and is pretty
straight forward. Above, you can see I am using the 4 receivers available
in the gateware version of the HL2 I chose. The image at the top of the
page shows operation during CQWW CW 2020, where there were huge numbers of
signals present on the bands.




You can connect a telnet program to localhost on port 7300 to connect to
the Skimmer Server by default. This acts like a DX Cluster with spotting
information.



Uploading to PSKReporter




One of the most easy way is use CW Reporter by Philip Gladstone N1DQ.
Philip runs PSKReporter, and, offers the CW Reporter application to
interface between CW Skimmer Server and PSKReporter. It is easy to set up,
working almost out of the box, and translates the DX Cluster style Telnet
spots into reports for PSKReporter.info.




One comment to note here is that you should have calibrated your receivers
frequency before doing this otherwise, you may be spreading incorrect
frequency information.








Finally, it is possible to see, on a map, using appropriate filters, what
stations I have heard on CW over the past 24 hours:








Click any image to enlarge.




Thanks to everyone who offered help and suggestions along the way!