[hpsdr] What is the best way to interface Hermes to a non standard filter/PA/Transverter network?

[Dick Faust]

Hi Rob

I can not find a clear schematic of the PA section, but it looks like it 
uses high side switching on the relays through some type of interface IC 
on bottom left of PA schematic.  Each filter has been individually 
selected previously similar to Alex which uses low side switching.
I did an alternate design for Alex so I could use Packer filters and I 
am finishing up the first units.  There is a document on my Munin2 page 
near the bottom that has the schematic and board layout info.  Hope to 
have a couple of pictures available in a few days. Give it a look the 
circuit may work if the inputs are true low in the connector to the PA 
board.
http://www.k9ivb.net/munin2/Alternate_Alex_Interface_V6.pdf
or the web page
http://k9ivb.net/munin2/

Dick K9IVB


Rob Frohne wrote:
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> Hi All,
>
> I've decided to hook my Hermes to the guts of an old FT-847 (that was 
> hit by lightning, wiping out most of the 5 volt logic) for the 
> bandpass filters, the PA units with their LP harmonic filters and the 
> the transverter units for 2 meters and 440 MHz.  The FT-847 uses a 
> clocked data input similar to the SPI or I2C that are available on the 
> Hermes board for Alex & Apollo, and shift registers similar to Apollo 
> and Alex, but the bits are defined differently to tell the the units 
> what band you are using, etc.  I'm mulling over the best way to fix 
> this little problem so that my maintenance headaches are as minimal as 
> possible.  Here are some options I have considered.
>
> 1)  Change the FPGA logic so that I get what I need on the Apollo/Alex 
> connectors.  (They are really wired in parallel, with perhaps a 
> different pin-out on the Hermes board.)  This means I need to apply 
> the patch every time Phil or someone else updates the Hermes firmware.
>
> 2)  Use a couple of the pins that are GPIO on J16 to make my serial 
> interface with clock and data.  This may also mean that I have to 
> apply a patch every time, but maybe not if I can convince everyone 
> that those GPIO pins are just as well used for this purpose.
>
> 3)  Use two of the three lines on J14 (labeled for future expansion) 
> for my serial interface.
>
> 4)  Do the mapping in the software.  I don't think this is a good 
> option, because software changes much more rapidly than hardware, and 
> the mapping probably is not always an easy thing, because Hermes has 
> options for different antennas, low and high pass cutoffs, etc. 
> whereas I need just which of the ten HF frequency bands for receive 
> (in order) and then low, medium or high HF transmit, or VHF transmit, 
> or UHF transmit, and then data regarding the attenuator and 
> preamplifier.  See the block diagram image 
> <http://people.wallawalla.edu/%7ERob.Frohne/FT-847/Filter_Interface.png> 
> of the FT-847 setup below, or the complete block diagram 
> <http://people.wallawalla.edu/%7ERob.Frohne/FT-847/FT-847%20Block%20Diagram.pdf>.
>
> Is there something I haven't thought of that is better?  I'm leaning 
> toward 3) the future expansion pins, but would like some advice from 
> those who have more experience than I do.  Suggestions?
>
> Thanks & 73,
>
> Rob
> KL7NA
>
>
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