VMAC ATV/DATV Audio Video Matrix Controller

[G8PUO]

Following a delay due to the Chinese holiday and shipping, the new VMAC RPI Lite boards have finally arrived! Populated and placed in SMT oven in order to test the revised layout. Once the SMT components were placed, the next stage was to add the through hole components such as RCA sockets, relays and connectors.



First board just out of the oven. All looking good, with just a couple of tweaks to the thermal profile, the board is ready to run.



With basic electrical board testing complete, powering up and then the sending some I2C commands to test the various IC's using the board connectors, rather than Zero. This enables some diagnostics from the PC debugger. Overall, all is looking really good for the first SDK board. Plan to run various tests and measurements in my lab over the next week and then hopefully the boards can be made available on our site.



The VMAC RPI Lite board will be provided semi-populated. This means that all the surface mount components will be added by us and all you need to do is add the though hole components where required. A couple of enquiries have been made about us providing a blank board and the builder populating the SMT components as well. This could be included as another kit option and we will look at putting together suitable instructions for this and a means to package the components. Should you prefer this option, please let us know your thoughts.

Software for the VMAC project is open source community based and the mechanism for this is being put together now and should be online very soon. The board being used for ATV/DATV repeater control logic, FM repeater control logic and home audio/video switching controller.

Further details can also be found on our HAMKit website, blog and social media. http://hamkit.co.uk http://hamkit.co.uk/Blog/ https://www.facebook.com/hamkituk/

The living VMAC documents can be found http://hamkit.co.uk/hamkit---downloads- ... ntent.aspx

We value all feedback as these can be incorporated in future versions of the VMAC boards and software.

Many thanks to all for the project support to-date, Dave G8PUO.

[G8PUO]

A question has been asked about the RCA connectors.



On the VMAC RPI Lite, you have a total of nine, three inline RCA connectors. The left six in the photo are inputs and the right three are outputs.

Should you wish to use BNC connectors, then you can easily wire the connections from the board (leaving off the RCA's), to the BNC connectors as required. Alternatively, use BNC to RCA adaptors (not the ideal but will work).

Inputs top (Yellow) is video, middle (white) is RX Squelch and bottom (red), is audio.

The RX squelch input could easily be a push button or other switching control which pulls the input to ground on signal. Diode protection is provided on the VMAC board to protect over volts on the input.

Outputs top (Yellow) is video, middle (white) is PTT and bottom (red), is Audio.

The PTT output is pulled to ground via FET (BSS138).

[G8PUO]

The VMAC RPI Lite running with a Raspberry PI Zero, mounted using a header male/female.

The Reset and Video connections are also taken from the Zero via the 2x2 pins below the main PI header.

[G8PUO]

For those with a VMAC PiHat, a new HAMKit Wiki page has just been added, complete with a bunch of test code and audio WAV files, allowing you to quickly test and setup your DTMF decoder.

Further details can be found at https://hamkit.co.uk/wiki/hamkit-wiki-p ... code-dtmf/

[KA5BBC]

I am currently working with one of Dave's V2.4 boards and it is quite the learning curve, never having use d Python before.. The quality of the hardware and the results so far are making it worth the effort. Dave's support has been invaluable.
This will be the core of our new repeater for north east Oklahoma which I hope will be functional on 440MHz and 5.8GHz in the not too distant future, and full time streaming on the BATC site also.

[G8PUO]

Good to know Andy, appreciate the feedback.

KR
Dave

[KA5BBC]

As much as I want to use the second of VMAC to provide an HD (component) pathway I might have to use it to build a second repeater for demonstrations.
The fact that you can use the VMAC for so many different configurations of AV ins and outs, especially with two VMACs connected together, makes it a very useful tool for ATV/DATV. I know that some will be bemoaning the lack of HDMI connections however a couple of cheap HDMI to/from component converters easily overcomes that.
I have also been looking at cross mapping the RPi GPIO header with other devices, Jetsons and BBB etc, and appears that we should be able to utilize it on most of them with minimal effort - possibly just an interface cable which does the cross patching.
One of the most interesting results of that I have had is that if I connect a cable TV headend demodulator (receiving digital broadcast transmissions and feeding component 16:9 SD NTSC) directly to the TV the video quality is at best adequate, most people would call it poor, but when the same demodulator goes through the VMAC and out to the TV (simulating video detect from a receiver and output to the transmitter) the video quality is greatly improved.
I am looking forward to continuing experimentation and build of this repeater with the VMACs.

[G8PUO]

Hi Andy,

If it helps, rather than use your 2nd VMAC for the demo repeater, as an advocate for STEM, I have one VMAC Lite (2nd stacked board for more inputs), left in stock and do not intent to make more unless needed.

So, happy to send you this one, at no cost and with our compliments.

Let me know!

KR
Dave

[KA5BBC]

Thank you Dave.. I will email you.