Cart Expander connector spacing?

[brain]

Revisiting my X-Pander 3 VIC design as I plan to get it up on Github and perhaps consider a re-run. It had bugs and I'd like to get them fixed before I put something into the wild.

Is there a preferred port spacing?

Also, as I recall, pin 20 and pin Y, though noted as N/C on many pinouts, were in actuality connected to something on some variants. Are there links to what those are, and do they need to be passed to the cart slots?

Jim

[srowe]

Revisiting my X-Pander 3 VIC design as I plan to get it up on Github and perhaps consider a re-run. It had bugs and I'd like to get them fixed before I put something into the wild.

Is there a preferred port spacing?

I've just checked the spacing in my Arfon expansion unit, the slots are 1in apart.

Also, as I recall, pin 20 and pin Y, though noted as N/C on many pinouts, were in actuality connected to something on some variants. Are there links to what those are, and do they need to be passed to the cart slots?

The wikit entry should be correct, Y is audio in on CR models. I'd recommend just passing them through exactly like all other lines.

[Mike]

I'd recommend just passing [pins 20 and Y] through exactly like all other lines.

There exist cartridges which misuse either pins 20 or Y on their edge connectors to simplify routing.

If one cartridge connects 20 or Y to +5 V and one other cartridge connects the same pin to GND you short the power supply.

IMO, pin 20 should be left unconnected to and between all cartridges, for pin Y maybe the first cartridge could have that connection to the expansion port in case it uses Y for audio in, otherwise from the second cartridge on there should not be a connection to pin Y either.

[brain]

I'd recommend just passing [pins 20 and Y] through exactly like all other lines.

There exist cartridges which misuse either pins 20 or Y on their edge connectors to simplify routing.

If one cartridge connects 20 or Y to +5 V and one other cartridge connects the same pin to GND you short the power supply.

My first design passed them directly through, and I got lots of feedback sharing similar comments to yours.

IMO, pin 20 should be left unconnected to and between all cartridges

TO prep the design for a push to GitHub, I updated all the symbols, including the edge connectors. My early design just used basic symbols and footprints for the edge connector, but I later created a VIC-20 specific symbol, with the named pins and such. In that symbol, 20 was simply omitted. When I updated the design, the trace simply disappeared (as it should, but it was nice to see it just resolve itself)

, for pin Y maybe the first cartridge could have that connection to the expansion port in case it uses Y for audio in, otherwise from the second cartridge on there should not be a connection to pin Y either.

On the update, I put in a surface mount jumper on the line, disconnected, and I have an option to make it switched. I'm toying with layout.

Thanks for the validation on the lines, I'd really like to not have to eat another 100 units (it was my stupid mistake, no doubt).

Jim

[brain]

I've just checked the spacing in my Arfon expansion unit, the slots are 1in apart.

I was thinking the same. Nice round number, easy to place on the PCB grid, gives a bit of space between, and keeps the design from being too long.

[brain]

I still need to shift the ports to 1", but I went ahead and placed the original and new designs on github.com:

https://github.com/go4retro/xpander-vic

Thanks to Orangeman96 on the forum for prodding me to provide the files

I've held off on shifting the ports, since the board is routed in two spacings (connectors are on .156 grid, while the rest is on .100 grid). The current spacing allows the grids to match up on the connector center lines. Thus, while it's not tough to shift the ports, it needs to be the last thing I do before finalizing the PCB design.

I took the liberty of routing the AUDIO line to the switches, for potential use. Maybe that's a bad idea, not sure, open the suggestions. If I remove the use of the switch, it'll just go unused, since I want to only stock 4 and 8 position switches.

I plan to make a small prototype run of both 3 and 6 port designs (1-2 of the 3 port, 5 or so of the 6 port), and then put the 3 port into prod. The 6 port can be a kit or PCB, unless there is more interest. It's probably a $50.00-$75.00 unit, though. the conns are not cheap, and the switches and such add up.

Suggestions on things to address appreciated

https://github.com/go4retro/xpander-vic ... %20PCB.png

Jim