ZX81+35 Clone

[mahjongg]

Micro-USB for power: has pro's and cons, but certainly not a bad choice.

Any chance of including that joystick connector on the board itself?

GPIO connector is a nice touch. Wouldn't be bad to have some more pins on that connector though. ZX81 people are rather 'hacking-minded' people, you know. So they'll find uses for whatever I/O pins you stick on there.

Micro USB, as a moderator of the Raspberry PI forum, I'm a fan of using a simple USB charger as a supply, I calculated my ZX81 clone would use less than 150mA, so its a good solution I think. Much better than a barrel connector, or even a 3.5mm mono jack, and a LDO.

The previous board had a DB-9 hard soldered on the side of the board, but I found out that it stuck out under the PCB, which (without a case) made the PCB with keyboard very unstable, I tried an angled DB-9 instead, but couldn't fit it due to size constraints. Perhaps I will make a new effort, if I can find an angled DB-9 that uses less space.

The GPIO header was carefully chosen, as a base the number of pins and layout was chosen so that you could directly connect to the 16-pin header of a text LCD like this:
Used in "Nibble mode" some pins were "unused", and I filled this positions as good as I could, with speaker pin's and the only freely available input pin. This is also about the maximum size of expansion connector I can handle.

For (much) more expansion I have the expansion edge connector, with real gold plated pin, so not a wobbly edge connector.
If you must connect a classic ZX81 device you can solder a strip of dual sided 1/10" striped PCB to a female header as an adapter, but I will probably create my own expansion boards. They can fit within the (planned) enclosure, a bit like the sinclair QL, the keyboard will stick out six centimeters (eurocard width) to the left of the ZX81+35 PCB, so I can have roughly 10 x 5 cm expansion boards inside the case.

[mahjongg]

Mahjongg,
you have to be rich to use Altium Designer.

Not really, I use Altium at work, so this rough mockup I could make after working hours.
Actually the board itself was designed with Ulticap and Ultiboard, but the 3-D rendering of Ultiboard isn't nice, and it cannot use .STEP files.
I do have an account to use the new cloud based "Free Altium" "circuitmaker", and have it running on my old laptop, but have not done anything with it yet.
Its a pity that circuit maker cannot import Ulticap schematics, or I would switch.
I used Ultiboard professionally for over ten years, but I cannot stand its bugginess compared to altium anymore.

[PokeMon]

Well I use DesignSpark which is free of charge (even for business), quite professional and easy to handle (up to 8 layers and theoretically 1 mil size).

I tried KiCad but found the concept of using keyboard and mouse simultaneously quite horrible and even the annotation process.
But there is a really impressive autorouter provided which is a separate product (Freerouter) - incredible fast and reliable.
In the version used 2 years ago, this was automatically installed but in the meantime installation is much more complex.
But if you ever try - worth to see. Faster than EAGLE and result is really acceptable (up to 95-98% within less a minute or so for a Arduino board).
And you can follow this action live - better than watching TV.
http://www.freerouting.net/index.php

What I want to say is - there seems to be a standard for exporting and importing netlists (EDIF format) but I think many commercial pcb software companies are not much interested in easy export/import functions. Damn.

[mahjongg]

I have a big aversion against autorouters, and have never used one, and probably never will.
Each time I tried one I was very disappointed with the result.
A good layout is an art.
I have heard of both DesignSpark, and KiCad, (and Eagle, obviously) and looked into them, but I try to avoid learning a completely new CAD system if I can help it. It seems KiCad is still not finished. Some say I should try to avoid using Windows, and use Linux instead, but I'm not convinced.
I installed (with some difficulty, as my old laptop did not support direct-X) circuitmaker, and it works, I can use it, but its slow.
At least I don't have to learn much for me to use it, as its much like Altium.

[PokeMon]

I don't use autorouting either and like to do the design myself.
If you are routing for commercial reasons the time you spend on routing may count as well if your boss have to pay per hour.

I tried some autorouters if provided from a pcb software package while writing an article about free pcb cad versions.
So some commercial ones which may be used for non commercial purposes for free as well.
Target 3001 was not convincing but Eagle was quite good till I saw Freerouting which could beat Eagle - not in speed (nearly) but in vias used.
Autorouters are parameter driven and choose the right parameters could be a science for itself.

I think in Freerouting you can make different attempts for different net classes with different size of tracks. This is more convenient and the result is more reliable and predictable than the Eagle router which simply can not be influenced easily. So doing the power tracks first and doing some corrections you could do a second run with signal class or even different signal classes with Freerouting but not with Eagle (as I remember correctly). Anyway I don't use Freerouter as I don't like KiCAD.

But the most horrible software tested ever was Fritzing. My god - maybe good for breadboard but not for pcb's.
After the result I got an attack of laughing out loud.

[mahjongg]

You mean you got an attack of the giggles? ("de slappe lach" in Dutch).
Fritzing is a joke, for NOOBS, not a serious design tool. It's only slightly better than taking a picture of your breadboard.
I don't think that an autorouter can help me do the designs I do any faster than what I can do, certainly because I have to throw away 99% of the tracks the autorouter has laid. Any autorouter that could be helpful will need so many help from me (with declaring the right design design rules) that entering the rules would take longer than making the design myself. Perhaps one day an artificially intelligent router can be learned these rules, and can be set up to create the right routing, for the right kind of PCB, but not autorouters like freerouting.
Also i really like routing, its my job (layout engineer), I like to keep my job, not being superseded by a bot.

[mahjongg]

Any chance of including that joystick connector on the board itself?

Well I reckoned that if I use a DB-9 male connector without a shell, like this one

Then I would have place, just for the 9 holes for the pins, I could do that.

what do you think, would that be a better option than eight holes in a 2.54mm pattern (pin-header).

[PokeMon]

In my eyes a 10 pin (2x5) Header would be okay, somebody could use this if needed (connector with flat cable).
http://www.reichelt.de/SUB-D-Flachbandv ... UB+ST+09FB

[mahjongg]

Yes, that is another choice that I have already considered, but I have to see which of these choices would fit, I now use a single row of eight pins and it fits,but I don't know if a dual row of 5 pins would fit, but if the shell-less DB-9 fits a 2x5 pinheader would fit also.

But RetroTechie explicitly asked for a DB-9 connector mounted to the board.

I'm also considering the cost, my current concept is cheapest (the DB-9 with solderlugs is very cheap, compared to the other options, especially the shell less DB-9 is very expensive, about eight times as expensive as the one with solderlugs.

Reichelts offering remarkably is about as cheap as my one with just solderlugs, but then if you want it detachable, instead of soldering the wires of the flatcable directly to the board, it becomes more expensive, it is more professional though. There might be a small problem with mounting it to the enclosure though, but that is not different from the one with just solderlugs.

The single 8-pin header would require soldering wires to header pins, and using a female 8x1 header, to make it detachable, which is cheap for a hobbyist, but not as professional.

[RetroTechie]

But RetroTechie explicitly asked for a DB-9 connector mounted to the board.

Of course there's no "must" in any way, it's mahjongg's project so he's free to decide how to design it.

Reason is simple though: the less work a user has to do in order to plug in a joystick, the higher the chance it'll be used. Buy some connectors and assemble them = work.

I'm also considering the cost

If this board is intended to be a 'product' some day, then surely including a joystick connector would be cheaper than buying board without connector + ordering connector separately. Sure there's "free shipping" from China, but those shops often sell the most common types only, and questionable quality at times. Respected distributors like Farnell / Digi-Key / Mouser etc will charge shipping, have minimum order amounts or only sell to companies. Alternative is a joystick interface, which is waaaayyy more expensive than a simple connector (and occupies the expansion connector).

But if low cost is important, you could consider designing the board to take connector type XYZ, and leave it unpopulated so users can buy/solder it onto the board. If you sell the boards yourself, you could make that a purchase option.

I'd be hesitant about pin headers for something with a standardized connector like a joystick port. It requires a [plug + wires + connector] assembly, and even if delivered with the board, loose bits 'n pieces like that tend to go missing over time. That even applies to original owner / builder of the board... Not to mention that extra connector + wires = extra points of failure.