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Old 20th Jul 2021, 4:47 pm   #5
Join Date: Apr 2018
Location: Newbury, Berkshire, UK.
Posts: 1,104
Default Re: MK14 Programming Interface

Originally Posted by Timbucus View Post
Oh cute - did you design a PCB in the end?
The PCB is a cobbled together thing that started life as a protoboard layout and was turned into a PCB. If I was doing it again I would make a number of changes, like using the edge connector footprint like I did in the Ortonview instead of a dupont header with cables so I could just solder the edge connector on to the circuit board, and the Pi Zero W hangs over the edge of the board so you can't put in a securing bolt, and its a bit of a squeeze to get the optocouplers under it to fit because they are close to the Pi connector..... But it all just fits and it worked.
Also the GPIO connector is soldered onto the bottom of the Pi Zero, so using a ordinary Pi would be hard, although you could probably do something with a ribbon cable and a couple of IDC connectors to get around that if you are careful with the pin mapping and orientation of the connectors.

Originally Posted by SiriusHardware View Post
You didn't have to fettle any of the time delays? For some some reason most people do. I'm guessing your issue VI has a VDU friendly 4.00Mhz crystal, which should theoretically make it even more sensitive to programmer overspeed - or maybe you currently have a 4.43MHz crystal fitted?

I see you've used a direct connection to the reset input (only available on your issue VI) for maximum neatness.
No, I left the time delays as standard. I am using a 4.43MHz crystal too. Guess I was lucky! I used the "key14" program to test all the keys worked, then tried send14 with the slothie.hex file. I discovered that the checksums put into the file (probably by my bin2hex program) were wrong, so I had to (temporarily) disable the checksum check in but I'll redo the checksumming properly and re-instate the check in send14. With permission I might even tinker with send14 to add some option arguments for timing etc.

The reset connections are brought out to a 4 pin header (which I've had to make right angle because it sits under the Pi ) so you can either jumper it with a couple of links like I have or connect 2 dupont style female connectors connected to croc clips if you dont have an Issue VI.

As for the I/O Ram, as I was typing this it occurred to me it would be easy to make a small board to take a couple of 2111/4 RAM chips that plugs into the RAM/IO socket and gives an extra 256 bytes for people without an 8154 (assuming you don't need the I/O)....!

If I can manage to find a way to get stuff posted to people (tricky at the moment due to being in a care home) I can post a board to anyone, as I accidentally got 15 made which is about 14 more than I need. If I work something out I'll announce it here. As I say its not perfect at all but was done quickly because I got the chance of some free PCBs!
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