Reviving a Multiplex Cockpit SX transmitter

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ReSt
Posts: 1533
Joined: Tue Dec 27, 2011 11:34 pm
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Reviving a Multiplex Cockpit SX transmitter

Post by ReSt » Mon Feb 17, 2020 6:16 pm

Some time ago I got a Multiplex Cockpit SX transmitter with defective electronics. As the mechanics of that transmitter are really good, I was hoping to rebuild the required electronics in the way of the ER9x.
I didn't want to have the voice module or a trainer connector as the original radio had it neither and there is really not to much space in that housing.

I sawed off the electronics part of the defective board and left the mechanical support for all the switches and trim buttons functional.
I replaced the original display with a graphical 126x64 pixel display (1.8", 128x64, ST7565 from EastRising [buydisplay on eBay,6.20$]), that, I hoped, would be supported by the software of the 9x.
The connector sequence of the display is more ore less the same, but inverted to the original 9X display, so not really a problem.

With adapter plates for the cpu (M128) and the display, a double sided proto board with tinned thru solderpads and packages of several values of 0603 smd resistors, 0.1uF and 1.0uF capacitors I started to assemble my mainboard.

As the circuit diagram of the 9x names two of the display control signals as "Read" and "Write", that's the naming convention for the 8080 8bit parallel mode (while the 6800 mode names them "R/W" and "Enable"), I wired my display for 8080 mode. But on the first times of power on, the display remained dead. When I finally changed the display mode to 6800 (it's only one pin moved from low to high), the display came alive. Due to the way, the display is mounted into the radio, I had to rotate the shown display by 180 degree. That can be done in the radio setup Display menu with "Rotate".
For the UP, DOWN, LEFT, RIGHT and EXIT keys I use a 5-way momentary switch, and the original scroll wheel with push button function as MENU key and scroll wheel. And the DOWN key also works as BIND button (had to disable the Quick-Select function od the program).

I was not able to flash the cpu via my USBASP programmer(s) that I use for all my other radios. I assume that is due to the fact, that my RC combination on the digital inputs is different to the "incorrect" way in the 9x radios. My switches go via a serial resistor to the input pin, where the capacitor goes from the pin to ground. So the capacitive load at the input pins is much higher and probably to high for the USBASP.
But from the early 9x times, I have a DIY parallel port programmer and Ponyprog2000 on one of my PC's. And this combination works flawlessly.
As I only use FlySky receivers, I use the rf board of an old Flysky TM-002 module.

Reinhard

Sequence of the pictures should just be reversed
Attachments
9.ready.JPG
8.finished.JPG
7.assembled board front.JPG
6.assembled board back.JPG
5.First successful power on.JPG
4.Processor board.JPG
3.Switches and new display connected.JPG
2.Display board.JPG
1.Main Components.JPG


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jhsa
Posts: 19247
Joined: Tue Dec 27, 2011 5:13 pm
Country: Germany

Re: Reviving a Multiplex Cockpit SX transmitter

Post by jhsa » Tue Feb 18, 2020 11:08 pm

Great work.. This is inspiring :D Thanks for sharing.. I believe there is space for a voice module and speaker in there ;) :mrgreen:

João
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