SoC Mk14 Pico Uploader

[DavidMS]

Originally Posted by SiriusHardware

Looking very nice so far. What sort of optocouplers have you gone with?

I chose the individual surface-mount TLP185 optocouplers for the original project because we had them by the bucketload at work, but it makes sense to reduce the cost and component count by using multi-opto packages as you seem to have.

I have nominally gone with ISP621-4X or similar - basically any quad opto with the correct pin out will work - I say that as for whatever reason CNY74-4H has reversed 2 of the transistor orientations .....

The main reason for using them was most efficient use of board real estate - without going down the surface mount route.

[Mark1960]

Originally Posted by DavidMS

This is basically what the corner of the PCB will look like (with some extra clues as to what each jumper does). Essentially right short for original and VI, left for JM Precision. Note the edge connector is duplicated on the underside


I have spent far too much time fiddling with the layout so once I have done a final check will send off for a few to be made.

If the pads to the left of the connector mounting holes are for soldering a connector mounted on the edge of the pcb you could extend them to 0.4mm from the board edge. It might also be usefull to have matching pads on the bottom side of the board for mechanical stability if a double sided edge connector is used.

[SiriusHardware]

I think DavidMS did say earlier that he was placing contact fingers on both sides of the PCB edge.

I would agree that with the possibility of various types of 0.1" pitch connectors which may be pressed into service, those contact fingers should be as long as they reasonably can so each finger has a large area attached to the PCB.

Of course we are probably saying this mere seconds after DavidMS pressed the 'order' button.

[ortek_service]

Originally Posted by SiriusHardware

Owen, there was never an official 40-key keyboard circuit. We talked about establishing a 'standard' key matrix for one ourselves somewhere in one of these threads but really an alphanumeric keyboard would be of little use without a matching output device (ie, VDU) and then a new OS written to use both.

Something like this was actually in the MK14 pipeline but instead, the decision was made to develop an all-new machine with integral alphanumeric keyboard, VDU and high level language - the ZX80, in other words.

Thanks for info. So as there wasn't an official 40-key keyboard, was there any / several other 3rd party ones sold / designs published?

Yes, one of the MK14 designers wanted to produce a more-advanced computer with a better-processor, but apparently Clive Sinclair wanted to stay with the SC/MP (before he must have eventually been persuaded to go with the Z80 and the Zx80). So they'd left to form Acorn, which did start-off using the 6502 on System-1 (Albeit also with basically the same Keypad & display), which could be expanded into System-2 etc with VDU and ASCII-Keyboard.
But I wasn't sure if you could produce the full Alphabet on any VDU boards for the MK14 - Chris is looking to produce some (updated with some more-available period components) 'replica' VDU boards, to get experirence with that
- As well as doing an enhanced MK14, with substitution of the expensive SRAM's, and PROM's, for cheaper & higher memory capacity SRAM's / EPROM, to support other SC /MP OS's like ELBUG. So was interested in also adding a full-keyboard (Especially if other SC/MP OS's of the time, supported one).

[Phil__G]

The next logical development of the MK14 would surely be a NIBL basic machine with maybe one 4k page of ram, very much like the PICL
or maybe Ronald Deckers SC/MP with NIBL and FP basic. NIBL is actually very capable and ideal for hobby & educational use, integrating well with SC/MP M/C.
Tim found some evidence of a SCRUMPI 4 from Bywood which would certainly have been a serious contender but for JMK's unfortunate passing at a young age

[SiriusHardware]

So as there wasn't an official 40-key keyboard, was there any / several other 3rd party ones sold / designs published?

Not to my knowledge. If there had been I feel sure Timbucus would have found it, as that is his superpower. We are starting to Hijack DavisMS's Pico-uploader thread here, so if we want to continue on the subject of 'enhanced' keyboards and applications which might have made use of one, we should probably start a new thread.

[DavidMS]

PICO uploader PCBs ordered

[SiriusHardware]

I would certainly be interested in buying one of your surplus PCBs from you David - I can never have too many uploader options...

[DavidMS]

PCBs arrived this morning, all very exciting

[SiriusHardware]

I assume you'll want to populate and test the first one yourself, but when you're happy with them please PM me with details of how I can order one of your spare PCBs.

[DavidMS]

Originally Posted by SiriusHardware

I assume you'll want to populate and test the first one yourself, but when you're happy with them please PM me with details of how I can order one of your spare PCBs.

Yes - Will do

[DavidMS]

After a bit of work related delay I have managed to get the PICO uploader board built and working. There are a couple of minor errors on the PCB layout but I was able to fix all but one by adjusting the s/w. The remaining one being the reset connection which I reversed, which is an easy mod. More annoyingly I assigned the button and jumper function text to a layer ignored by the gerber generator - hence the labels. The s/w is functional but I need to do a bit more work on the setup function. I am away with the day job this week but should get some time in the evenings to do a bit of write up.

[SiriusHardware]

Looks very promising, it could become a regular on the exhibition circuit as it looks so easy to use and self-contained in a similar way to Coolsnaz2's M5Stick setup.

[DavidMS]

I have finally managed to upload an initial set of documentation to github and copied here. The s/w is still somewhat raw around the edges but is functional - it's certainly not pretty. The hardest bit to get sorted had nothing to do with the core functionality, but was around updating menu settings - It is written in CircuitPython which while offering some advantages over micropython does not offer an elegant route to manage multiple sources wanting to write to the file system. Anyway here it is. I will try to do a bit of tidy up of the s/w over the next week. I have not posted Gerbers as this stage as there are some minor errors on the V4 PCB and want to avoid putting something out which I know is wrong.

https://github.com/DavidMS51/Pico-Uploader.git

[SiriusHardware]

Thanks for your continuing work on this - if you want to offload one of the not quite perfect PCBs I think I can cope with having to swap the reset-out connections.

[SiriusHardware]

DavidMS was kind enough to send me one of his current-issue (V4) PCBs for this project (Thanks David) and I have it about 95% built as I write this. Just have to finish it off and try to find a time slot during which I can actually try it out at home. (At the moment, work is somewhere I come to for a bit of peace and quiet).

[SiriusHardware]

I've just noticed a possible issue with the instructions for setting the links for the reset output. When SOC modified the circuit to remove the unwanted PROM images in issue V PCBs they had to 'borrow' one of the gates which had originally been used in the reset circuit input, and because of that the reset switch circuit was modified with the +V end of the reset capacitor hard connected to +5V and the resistor going from the capacitor -Ve down to 0V.

In the arrangement for original MK14s you have assumed that the +VE end of the capacitor is always connected to the input of the reset circuit, but on an issue V, tying the reset opto-output emitter to 0V and having the flying lead going to the capacitor +VE lead will attempt to short the +5V supply to 0V, although the limiting resistor R1 will ensure there is not an actual short.

That is why, on the original Pi-uploader design, the reset-output opto-transistor's emitter is not taken to the 0V track which all MK14s have on the keypad edge connector - instead it is taken out on a second flying lead which is intended to be connected to the reset capacitor -Ve and not specifically to 0V.

So for original MK14s (or specifically for the issue V, of which Martin L's Czech replica is an exact clone), the user will need two flying leads coming off the interface and going to the capacitor +Ve and capacitor -Ve. The reset-opto's emitter should not be tied to 0V.

[DavidMS]

Originally Posted by SiriusHardware

I've just noticed a possible issue with the instructions for setting the links for the reset output. When SOC modified the circuit to remove the unwanted PROM images in issue V PCBs they had to 'borrow' one of the gates which had originally been used in the reset circuit input, and because of that the reset switch circuit was modified with the +V end of the reset capacitor hard connected to +5V and the resistor going from the capacitor -Ve down to 0V.

In the arrangement for original MK14s you have assumed that the +VE end of the capacitor is always connected to the input of the reset circuit, but on an issue V, tying the reset opto-output emitter to 0V and having the flying lead going to the capacitor +VE lead will attempt to short the +5V supply to 0V, although the limiting resistor R1 will ensure there is not an actual short.

That is why, on the original Pi-uploader design, the reset-output opto-transistor's emitter is not taken to the 0V track which all MK14s have on the keypad edge connector - instead it is taken out on a second flying lead which is intended to be connected to the reset capacitor -Ve and not specifically to 0V.

So for original MK14s (or specifically for the issue V, of which Martin L's Czech replica is an exact clone), the user will need two flying leads coming off the interface and going to the capacitor +Ve and capacitor -Ve. The reset-opto's emitter should not be tied to 0V.

Ok thanks I see what you mean I will amend the instructions - luckily I included jumpers on both lines

[SiriusHardware]

This is how mine is getting on so far. I used individual surface-mount optos because we have a lot of them at work and I used the same type on the Pi-Uploader so I know they work OK for this purpose. The pins on the SM optos only just reached the pads intended for DIP parts but in a way that was a good thing because it forced me to position them very precisely and make a neater job than I might have otherwise.

I don't have a JMP replica so I've hard linked the jumpers for 'normal' MK14 keypad connection layout. I've gone with a right angled pin row connector for the output connections because my already existing Arduino version of the uploader has the same type of output connection and a ready made connection cable+ 16-way edge connector, so that will speed things up a bit. I haven't fitted the backlight resistor or links yet.

Now I just have to find the time to load the PICO up, when I can get a bit of time to myself.

[SiriusHardware]

I've just stolen a few moments to shovel the software onto the Pico - It's now come to life although unfortunately it turns out that the display I picked out of a pile of junk somewhere has some vertical Pixel lines missing.

I'll let you know when I've actually had a chance to try uploading with it.