Yet another MK14 vdu card

[Mark1960]

I’ll just be a spectator for now on this one. I have quite a few things taking up my time for now. Shipping to Canada is an added cost, together with any possible customs issues for a kit and I don’t really want to set up a programmer for a different cpld.

I’m impressed with the progress so far, especially the space invaders.

[Realtime]

Originally Posted by Timbucus

Yes I would of course love one and I have used a DIN41612 female (the PCB straight mount type) soldered directly either side of the Issue VI fingers. .....Did you put the holes for a right angle Euro on the PCB or do I need a straight one to solder to PCB fingers?

The right angle connector should fit. I'll get a spec sheet for the 41612 connector and make sure it's compatible and let you know. The photo shows the connector pad arrangement (0.1" spacing).

Originally Posted by Timbucus

I did try my Issue VI with home made RAM and SOC VDU Replica but, as the mapping for INS control was not the same as mine - I usually only use main RAM for screen it would not run and I do not feel up to doing a code mod at the moment.

OK, look forward to hearing something once you feel better.

[SiriusHardware]

Here (attached) is MK14 invaders running on my Slothie-Ortonview, photographed directly off the screen of my Philips Composite/RGB video monitor. On this occasion I didn't connect port B to the VDU control lines - on the Slothie-Ortonview PCB the port B lines from the issue VI don't go any further than a row of holes intended to take a pin-row connector - at the moment I don't have anything in there so I forced the control lines to the required states using the DIL switch on the VDU PCB.

I will need to make some alterations to the 'bridge' board which I use to connect my original SOC VDU to the issue VI - there is currently no provision on that board to use port B as the VDU controlling port, but I will take it to work and make the necessary mods.

It's genuinely fun to play - I managed to get through quite a few waves until it killed me off at only one point short of 100.

It's quite unforgiving because the bad guys fire on you the instant they are over the top of you. I noticed another (harmless) quirk - sometimes one of the high level baddies will drop a bomb when they have a clear line of sight to you, but then they all move and one of the low level baddies slips in underneath and the bomb lands on top of the low level baddie - it does no harm and disappears a moment later.

I'm glad I have good quality low-force tact switches fitted to my issue VI, I don't think I would have done so well with the rubber sandwich keypad which was fitted to my original issue II.

Tim, if you are thinking of letting people play this at the show, consider making up a 3-key 'gamepad' box with three tough arcade type switches on it, wired to the keypad edge connector.

[Mark1960]

It looks like the 64 way connector pads on Realtime’s pcb is spaced to suit an a+c connector, but Tim might be using a+b.

Just thought I’d ask for clarification to hopefully avoid a mismatch.

[Timbucus]

Well spotted Mark - yes I am using an a+b so they will not fit (i.e. as per the original SOC VDU). No problem though - perhaps the best idea would be to have a standard connector fitted and get a small converter PCB made up.

In this instance though as so few connections are made to the top I would probably just bend out the pins slightly and patch them into where needed as I would not want to change out my whole infrastructure of interchange as I have my breadboard set up that way.

[Timbucus]

Originally Posted by SiriusHardware

Tim, if you are thinking of letting people play this at the show, consider making up a 3-key 'gamepad' box with three tough arcade type switches on it, wired to the keypad edge connector.

Great minds - I have a cunning plan - watch this space...

[SiriusHardware]

Thinking about it, the keypad 1, 2, 3, keys share a common line on one side so you could take a simple Atari-wired joystick and wire:-

Joystick switch common to the keypad '0-1-2-3-4-5-6-7' line

Joytick left-out to the keypad 1-9-B line

Joystick Fire-out to the keypad 2-Go-C line

Joystick right-out to the keypad 3-Mem-D line

However, anyone using a joystick would almost certainly try to fire at the same time as holding the stick left or right - I forgot to notice whether I could fire with one of the direction step keys held down - also with a joystick people will instinctively expect that the 'ship' will keep going left if the joystick is held to the left, and keep going right if the joystick is held to the right. I should have tried holding down L or R to see if the ship would keep moving but my guess would be that it moves one step per key press/release.

[Realtime]

Originally Posted by SiriusHardware

Here (attached) is MK14 invaders running on my Slothie-Ortonview. I managed to get through quite a few waves until it killed me off at only one point short of 100.

Excellent stuff. That's probably the most extensive test it's had. I've never got past 50 points. The points counter is actually limited to 99 to fit on the screen, so you may have already exceeded 99 without noticing. The counter could be extended to a 3rd digit if POINTS was changed to PTS. It would need a bit of code optimisation to free up a few extra bytes though.

Originally Posted by SiriusHardware

I noticed another (harmless) quirk

I bet there's quite a few quirks lurking in there. If anyone makes any improvements to the code then make sure you share them. It would be nice to see it develop further.

I love the way this has already spawned potential additional HW in the form of a Games Controller pad/joystick. I had thought the same about external switches but a joystick would be much better. The keypad interface is polled every game cycle (about 80ms I think) so holding down a key will result in a continuous left / right movement. Only one bullet can be on screen at any time and because the keypad is decoded looking for just one data bit to be active I don't think you can drive sideways and fire simultaneously. That may make a joystick less usable perhaps. I'll check that at lunchtime.

[Timbucus]

Sirius - that was my idea exactly and I proposed connecting Up and Down to 4 and 6 as well for future game use... Using the idea of the old COMCEN Spectrum joystick I was going to have a header for the 6 rows so that any 0-7 could be wired for anything - e.g. PONG



Then it occurred to me that modifying the software would probably be less hassle moving between games to all use keys in as above. After all this is the first Joystick interface for the MK14 we know about so it is now the "Kempston" of the MK14 world.

Looking at the key routine for Invaders it does scan and act on all three keys so should fire and move at the same time.

[SiriusHardware]

Objection!

If we already have 1=Left, 2=Fire, 3=Right, then why wouldn't you use 0 as down and 5 as up? Or were you thinking in more general terms, not just for the Invaders game?

Pong (proper Pong) IMO would be unplayable with anything less than analogue controls.

[Timbucus]

Actually I was thinking on the fly it was easier to move your left hand up one key for UP and the same for your right for DOWN but, that star layout does seem to make more sense in both contexts of using the keypad or a stick - I will change it before I build it. So changed by the standards committee

[Timbucus]

Originally Posted by SiriusHardware

Pong (proper Pong) IMO would be unplayable with anything less than analogue controls.

Agreed - PONG on the MK14 is very hard with only keys... I must finish building my PONG board soon as it is its 50th year - I have all the chips just no time.

[SiriusHardware]

It needs that finesse of being able to catch the 'ball' at just the right part of the 'bat' because that lets you change / choose the return angle, or so I seem to remember. You can only get that when you are able to whizz to about the right position and then fine-tune just before the ball hits the bat.

At the moment there isn't really a PONG game for the MK14, Milan's game more closely resembles the 'squash' game which was found as one of the options on the classic GIM AY-3-8500 based TV video games.

Regarding the 'star' layout for the joystick 'keys' it is true that on a game where you need simultaneous access to both the up and down and left and right keys your fingers would be playing the equivalent of a game of Twister. I still prefer that as a default though.

[coolsnaz2]

Just a couple of photos showing Invaders running on Replica MK14 using Raspberry Pi as the MK14 VDU.

Great game to demo Realtime's new VDU design.

[Realtime]

Originally Posted by Timbucus

Looking at the key routine for Invaders it does scan and act on all three keys so should fire and move at the same time.

Just checked and yes, if you are moving left/right you can shoot a bullet at the same time.

[Realtime]

Originally Posted by coolsnaz2

Just a couple of photos showing Invaders running on Replica MK14 using Raspberry Pi as the MK14 VDU.

Fantastic. That display looks really crisp. Nice job!

[SiriusHardware]

Just checked and yes, if you are moving left/right you can shoot a bullet at the same time.

It's good to have that confirmed, so it looks as though MK14 Invaders is an intrinsically joystick-friendly game. The race is on, who will be the first person to play MK14 Invaders using a joystick? (Hint: It will be Tim).

I still need to mod my issue VI - > original SOC VDU connection (and RAM expansion) card before I can show Invaders running on a genuine SOC VDU. Am I the only person here who has an original SOC VDU in running order, I can't remember? (Tim's is one of the very accurate Czech replicas, of course).

Moreover, is there anyone who has a suitably configured original MK14 + VDU + Extra-Extra RAM that they can try to run Invaders on? Mine is issue II, so it doesn't have the memory hole at 0200-07FF and it is far too precious to start hacking about with now - nor does it have the lower side contact fingers on the rear edge connector, they only appeared from issue IV onwards. An issue IV would still need to have the unwanted ROM images removed from 0200-07FF.

[SiriusHardware]

Just remembered, Coolsnaz2 has an original VDU and issue V MK14 and I'm sure he also added a RAM / ROM expansion into the 0200-07FF memory hole as well? - so he may well be the first to be able to run Invaders on an original MK14 and original VDU.

[coolsnaz2]

SiriusHardware

You are correct, but currently my backplane only accepts either the VDU board or my additional memory boards, see attached photos. Also my RAM/ROM expansion currently has the ROM configured at 0200 to 03FF, so Invaders would not work unless I modified the expansion board.

I have had a quick look on Amazon to see if I could get a extension ribbon cable with 1 male and 2 female sockets attached, but no luck.

[SiriusHardware]

I don't think I have ever seen a cable mounted DIN data connector unfortunately - they seem to have been used almost exclusively on card edges and card backplanes.

There obviously would be some advantage in being able to install the VDU and the RAM at the same time - the original VDU is really not much use when it is taking up 512 bytes of a fully expanded MK14's 640 byte memory.

Your dual-port RAM board is all RAM isn't it - that black ribbon cable in the 4th picture is what goes to the Pi currently, could you unplug that and plug in a short 40-way IDC female to IDC female lead which would then go to a small converter board with a 40-pin male to 32+32 way DIN data connector converter built on it? In other words, provide for the SOC VDU to be able to be plugged into the secondary port of the dual-port RAM board instead of the Pi?

I assume most of the required signals are on the 40-way IDC connector but you would probably have to feed the MK14 clock through to drive the VDU timing chain, or fit a 4-pin 4MHz oscillator module on the converter board.