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Old 28th Nov 2018, 9:46 pm   #1
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default MK14 programming interface - MK2

Over the past few weeks I have been putting together a new MK14 programming system. I made one which worked perfectly well back in 2012, but it was quite physically complex and not really a suitable project to put into the public domain for other people to build.

Here is the 2018 version.

-Like the original interface, fully isolated so that the interface can be connected to / disconnected from a running MK14.

-Uses only 12 optocouplers in a less complicated layout compared to the original project's 20, greatly simplifying construction.

-Directly controlled via a Python program running on a late model (40 pin) Raspberry Pi, such as the Pi Zero used on this one.

-An (optional) thirteenth opto allows the interface to reset the MK14, so that if it is already running a user program the interface can force it back to the monitor in order to programme it.

-The python control software looks out for two bytes in the file at address FFFE/FFFF, not a real address on the MK14. If it finds them it will take those two bytes as the Hi/Lo bytes of the execution address and will run the program automatically after the code has been typed in. (For those not familiar with the MK14, the first byte of an MK14 program is not necessarily the address from which the program has to be run).

The above two features combined form a hands-off development system for the MK14, since you can can then continually modify, download and run programs on the machine without having to touch it, unless of course your program requires keypad input.

Here's the hardware. It's built on stripboard, because it is simple enough to build on stripboard. I chose to use SM components because I have easy access to them and soldered them on the track side, but it is just as easily built using conventional components.

I'll add the python control software (which is working) and a couple of example .hex files of programs from the MK14 manual to upload with it in due course.
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