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Old 10th Dec 2020, 6:43 pm   #101
Mark1960
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Default Re: MK14 programming interface - MK2

Quote:
Originally Posted by Timbucus View Post
I debated if this was the place to document this to some extent but, my current project needed an ASCII keyboard and a way to type in BASIC programs. So this topic may get its own thread eventually as might my Triton - anyone out there with one of these ETI machines that makes it worth starting a thread?
I don’t have a Triton, but would be interested to follow the details of your restoration and any other hobby computers of the same era. I have that November 1978 issue of ETI in a box somewhere though probably easier to find on world radio history web page.

That keyboard interface was probably intended to use a 2736 type keyboard encoder, they were quite common back then. I have a couple in white ceramic that I keep planning to rig up to a keyboard for my Microtan 65. Last time I had it running was with a 64K z80 board used only as a keyboard encoder.

Another easy interface might be to use an FT245 module.
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Old 10th Dec 2020, 10:07 pm   #102
SiriusHardware
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Default Re: MK14 programming interface - MK2

You could also use a big PIC to scan all the lines of a full sized keyboard and output your parallel code + strobe, if you didn't feel that was too un-retro.

Or, use the same PIC to bit-bang the serial data+clock communication protocol for a PS/2 keyboard and translate the output from that into the parallel data + strobe format required by your Triton mainboard. That will relieve you of the chore of having to make the keyboard.

There appears to be an Arduino Library "PS2Keyboard.zip" (for communicating with a PS/2 keyboard) here:

https://www.pjrc.com/teensy/arduino_libraries

Just add the bit which translates the output from the PS/2 keyboard into the parallel codes expected by the Triton.

Last edited by SiriusHardware; 10th Dec 2020 at 10:15 pm.
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Old 11th Dec 2020, 12:29 am   #103
Timbucus
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Default Re: MK14 programming interface - MK2

That is pretty much my plan - as the PIC will look like any other 40pin keyboard chip of the time. I will create a Triton thread for discussion on the machine as it seems people may be interested
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Old 11th Dec 2020, 1:33 am   #104
SiriusHardware
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Default Re: MK14 programming interface - MK2

Use of a PIC or other microcontroller potentially has one further advantage. The mid-range onwards devices all have built in UARTs you can arrange to receive keycode input via the serial interface from a host / programming PC as well as from keypresses on the actual keyboard. In either case the keycode received or key pressed is translated into the corresponding parallel code + strobe which the Triton expects.
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Old 18th Dec 2020, 10:15 am   #105
SiriusHardware
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Default Re: MK14 programming interface - MK2

Another thought about the above, if you were using a UART-equipped microcontroller to both scan the keys of a full sized keyboard and accept keypress codes via serial input you might as well go one step further and have it transmit any local keypresses out via the UART, so that the keypresses can be 'recorded' and saved by an external host / computer.

Later, the host can then send all the typed characters back to the Triton and 'type' the program back in either at original human speed or at 2x, 4x, 8x, 16x speed etc.

Similar principle to Milan Humpolik's MK14 uploader which not only inputs keypresses to the MK14 like the ones discussed here, but can also record and replay keypresses as well.
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Old 18th Dec 2020, 6:24 pm   #106
Timbucus
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Default Re: MK14 programming interface - MK2

Yes I did think about that but, I will only have serial in featured as there is a bit banged serial out on the Triton which would be more useful to have as the output line as you can then get stuff that is loaded into the machine back out as well... having the serial in on the KB (converted to parallel) is the only option unless you add an expansion card or tap off the AY UART used on the Cassette as there are no other input ports.

See https://youtu.be/h-l5eP4cEFA for an example of how useful that approach would be and to see the HEX uploader now working as well as the ASCII keyboard script. Once I have the BASIC one working I will upload both scripts here.

I also plan to modify the script to have a small high speed loader uploaded that allows you to bypass the Monitor key routines and use the 8 bit port directly for faster loading of memory - a fully expanded 48K Triton would take an age to load up otherwise. I have been toying with using the final spare output (bit 6) to allow the Triton to generate a clock pulse so the data in can be 8 bit clean - the use of Bit 7 on Port 0 as a keyboard strobe is purely a software thing in the Monitor. In reality Port 0 is a plain 8 bit input port. So you effectively have two bits of output and 8 bits of Input to play with.
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Old 18th Dec 2020, 7:08 pm   #107
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Default Re: MK14 programming interface - MK2

An interesting watch, thanks for the credit but I think your project is now sufficiently far removed from the original one as to call it your own (I have always said that I consider the original uploader project to be public domain, for anyone to do what they want with).

What format do you intend to hold your BASIC programs in as a source for the uploader to use? The exact characters that a human user would type in, or something else?
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Old 18th Dec 2020, 7:31 pm   #108
Timbucus
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Default Re: MK14 programming interface - MK2

My plan was simple ASCII as that I think is how the Triton stores it - although I need to do some digging on that front to confirm. What I was finding though in testing is if there is a SYNTAX ERROR it all goes pear shape so being able to see the data or writing some custom code to ACK coming back somehow to spot an upload error will likely be necessary for longer programs.
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Old 18th Dec 2020, 8:24 pm   #109
Slothie
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Default Re: MK14 programming interface - MK2

Some of these early BASICs (especially those based on Microsoft BASIC) tokenise the lines as they store them in memory, which takes a small amount of time, so it may be wise to build in the capability to pause for 100mS or so after each "newline" to allow time for this to happen.The delay can sometimes get longer as the program gets longer.
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