BATC Forum

Portsdown band switching was originally only intended to control the Local Oscillator filter used with the Filter-modulator board. It has evolved into a system for controlling multiple transverters (and gains, levels and Contest Numbers), but needs a full overhaul to cope with emerging requirements.

I have designed a new system that retains backward compatibility with the use of the Filter-modulator board but, with external decoding, could switch equipment for up to 16 bands. This will be implemented in the Portsdown 2020 and the Portsdown 4. However, Portsdown 2020 users of the 3.5 inch screen will be limited to external control of 8 bands, as the 4th output line is used by the old touchscreen.

The general principle is that I have added a 4th GPIO output line, so there are now 16 codes. This means that I can define 2.4 GHz as a direct band or a transverter band. The same for 50 MHz and 3.4 GHz. I have also added designations for 47 GHz and 76 GHz. Many of you will still need bespoke translation after the Portsdown to manage your own transverter and driver switching, but this change should enable it all to be controlled from the Portsdown without ambiguity.

There will be a new band selection page with all these options, and more storage for power levels and Contest numbers etc. The 16 codes at the bottom of the table can be used as override, just like in the existing system.

Details are below. Please let me have any comments so that I can consider them as I implement the design.

Table updated to Version 0.3 to correct an error. Thanks Colin!

Dave, G8GKQ

Hi,

thanks for the information, Dave.
You wanted comments, here's one of me

One or the other GPIO of the Raspie has no clear value when switching it on and off. It's difficult sometimes.

What speaks against the implementation with an MCP23017, as with the Langstone?

On the one hand, you are compatible with each other and it works great.
When switched on, all outputs / inputs have defined states and finished boards are not expensive.

Then there are no problems with the limitation from Portsdown 2020.

Thanks for the comments

It would only take a single call from rpidatv/scripts/ctlfilter.sh to an MCP23017 driver utility to incorporate support for the the MCP23017 for band switching.

If someone were to come up with a demonstrated working implementation and provide me with detailed instructions on how it should be integrated in the current Portsdown build, I would be prepared to put it into the production releases as an untested, non-maintained capability.

However, due to workload and equipment limitations, I would not be able to test the capability on new releases or provide any assurance of its continued functionality.

Colin and John's developing solution using an Arduino and relay switch boards moves the switching problem out of the Portsdown domain and isolates it from Portsdown changes. I much prefer their approach.

Dave, G8GKQ

Arduino and relay boards (16 relays for around £10) are cheap and easy to program. I used these to control GB3NQ (with a lot of mehanical building help from others). Basically a 12v to 5v buck convertor can power the boards and the arduino drives the relays through opto-isolators. In the repeater controller the relays switch the video between 4 Rydes and a quad split to the transmitter while also looking after the powering of the raspberry Pi and transmitter switching.
In a Portsdown system the arduino and relays could control the powering of the RPi, the band switching and linear amp power. That would still leave other things it could do. Using hats on the arduino things like GPS could also come into play.
Some sort of standard approach would be useful though.

Martin G8LCE

Hi Dave,

I include the mcp23017.py in the controlscript of our ATV repeater DB0OV.
We control 2 pieces of MCP23017.

The function of mcp23017.py can be tested with the mcp_test.py script.

Here to download:
https://www.dropbox.com/sh/9asi644qarfv ... aIsUa?dl=0

The public code is from : http://www.gsurf.de/page/2/

Hi Thomas

Sorry, I need more than this. If this capability is going to get implemented, I need to know exactly what modifications to make to which Portsdown files. As I said, I do not plan to do any testing of the capability.

So, if you were to implement and test it, I'll put the modifications that you send me into the next release. Remember that I'll need proposed modifications for both the clean install and the update scenarios. You could fork the https://github.com/davecrump/portsdown4 repo and send me a pull request. And you'd need to do the same for the https://github.com/davecrump/portsdown-buster (Portsdown 2020) repo as well.

Thanks

Dave