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Monday, 06 August 2018 16:22

BATC Portsdown driving the DATV Express

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Running the DATV Express board with Windows software requires a fair amount of computer power; an i7 processor just about copes. When you get it right the output from the Express is superb;It's not a cheap board but the excellent filtering justifies the cost.

My latest project makes operation of the DATV Express much simpler and uses less processing power. The system consists of the front end and software developed for the BATC Portsdown transmitter. While the Portsdown will run as a standalone multiband transmitter it also has the capability to drive the DATV Express board. Linux based; the software in conjunction with the Raspberry Pi 3B + makes a fast and compact front end.

After taking the various components out on portable operations I decided to construct a complete package to tidy things up. Today I finalised what I will refer to as the head unit. Some tips for my build came from Noel G8GTZ who also saw the benefits of this system.

I will show some pictures and describe what I've done. The DATV Express and associated component parts (Base Unit) will be discussed and posted in a later blog.

Given the increased touch sensitivity and clarity of the 7 inch Element 14 screen I decided to use it instead of the 3.5 inch Waveshare used in my Portsdown Transmitter. Noel G8GTZ pointed out a very nice case for the screen which can be got from MODMYPI. In the picture below you can see the 12 Volt power conversion on the back. I've also drilled the case and fitted an additional audio output as the unit won't fit my shelf with a jack plug sticking out the top.

 

So there are brightness issues with some LCD screens when viewed from above and I understand the 7 inch Element 14 screen is no exception. Not sure how much truth there is in it but I'm lead to believe the manufacturer decided to invert the screen to solve the problem. Whatever you'll find the picture is upside down in this case; unless you do as I did and use a software solution to put it the "right way" up. If you use it as is; the rubber feet will be on top and you'll need to make a bracket to hold it upright. In my situation the "Head Unit" will be above my eye level so no problem having the case round the right way. More on the software fix later.

 

In the next picture you can see the contents of the box I fitted to the back cover of the case; it consists of of a Chinese made DC-DC buck converter board to allow 12Volt input. There are a couple of additional filter components and a 5 watt zener diode crowbar at 5.6Volts. The Chinese board is rated to 3 Amps but gets scary hot; there are vent holes top and bottom of the box and it has run for many hours.

 

My completed head unit will require just one cable to connect to the base unit; a good quality USB cable. At the base unit the USB cable connects to a 4-way powered USB hub. The USB cables I use are the same brand as recommended for use with the BATC MiniTiouner; Lindy Cromo.

Two software mods were made to my Portsdown installation; neither have thus far been undone by the routine Portsdown updates. The first is the fix to put the LCD up the right way; you don't need this if you're happy to use the MODMYPI case upside down. Find the fix here on Github rpi-touch-display-fix

My second software mod allows command line adjustment of the Raspberry Pi sound level; see my blog entry here.

 

As usual this item was rushed; if I missed something please ask using the home page contact menu.

73 Steve

Read 231 times Last modified on Saturday, 22 December 2018 10:20

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