Saturday 25 July 2015

Patriotic Display

My TenTec Patriot is usable but user-hostile without a display. Fortunately, adding a display is the work of moments...

I haven't had many moments to spare since getting back home from the USA, but I found the few required recently and so - as you see above - the Patriot can now tell me what it is up to.

Adding the display is easy, as the heavy lifting is done for you - if you are content to attach a 20*4 LCD alphanumeric display over the standard ("Hitachi") interface. The interface is already accommodated in both hardware and the factory code. There is even a (poor) description of what to do in the user manual and a (much better) description in the comments within the factory code.

Here is a blow-by-blow account of how to do it, with some pictures to make it clearer for those who are not so familiar with these things.

Here is the relevant extract from wa4cdm's code ...

As you see, you need power and six lines to the display.

Here is the wiring you must arrange at the display end...

The LCD will have the usual 14 pins of the "Hitachi" interface plus two more for the LED backlight. Only four lines of the eight-bit data bus are used - the rest are left unconnected.

A simple trimmer potentiometer is used to set a bias voltage which makes the display readable. The comments in the code specify this as 10k - but the value isn't critical - I used 1k, because I had one at hand. Adjust this to get best results on the display. Too far one way and you'll see solid "bricks", too far the other and you'll see nothing.

You will need to run eight wires to the inside of the Patriot case - and you'll have to take the case top off to do this (remove the four screws at the side plus the nut and washer on the antenna socket). I had a scrap of ten-way ribbon cable about a foot long to hand, so I used that. I left all ten ways in place - perhaps I'll add some more push buttons or something in future with the extra two wires.

At the "Patriot" end of the wires you'll need to terminate on a 1*6 male 0.1 inch header strip and a 1*2 strip (or individual pins).

The relevant connection points - which are female headers -  are seen on this annotated section of the board layout...

and on this photo of the same area (the relevant connections are identified by the red boxes)...

Pass your cable through the rectangular aperture in the back panel (of the case top) and plug into the relevant connections, as shown below...

then reassemble your case.

Assuming your wiring is all correct, the display will work with the "factory" code - with no modifications required to the software at all - the factory software is already sending all the configuration commands and data (thanks to Stan, AK0B, for pointing out that the original version of this post didn't say anything about this important dimension).

The Patriot is a whole lot more user-friendly with a display.

Makes you wonder why it didn't come with a display (obviously the price of the case would increase dramatically) and why the instructions for adding one are presented in a manner clearly visible to those who already know how to go about doing it for themselves, but somewhat obscured to newcomers.

Funny old world.

...-.- de m0xpd

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