A500 trapdoor memory: free design

[katarakt]

Fantastic, well done PeteAU

So...i'm not a pcb specialist, but in rev.b outline layer 19 was incomplete but maybe you've fixed this too? I'll check tomorrow.

Oh, would be nice if someone can give an updated bom for SMD RTC version and overall miniA501b3.zip with the new gary.

edit: just checked the new miniA501b3_gerbers.zip ...board outline file is missing, i think layer 19 is still incomplete?

[PeteAU]

Originally Posted by katarakt

Fantastic, well done PeteAU

So...i'm not a pcb specialist, but in rev.b outline layer 19 was incomplete but maybe you've fixed this too? I'll check tomorrow.

Oh, would be nice if someone can give an updated bom for SMD RTC version and overall miniA501b3.zip with the new gary.

edit: just checked the new miniA501b3_gerbers.zip ...board outline file is missing, i think layer 19 is still incomplete?

The outline file is .GML and looks fine to me. The unrouted 19 is just some signals that we don't want to route from the main board to gary.
Go on, splash the $4.90+post and give it a go

[Mathesar]

Originally Posted by PeteAU

Hi,
Please somebody check it for obvious errors. Any 2nd pair of eyes is welcome.
Done! But wait until somebody checks this revision, there might be errors.

This project is getting nicer and nicer (and popular it seems )

I had a look at the PCB layout again and I am wondering if we can improve the decoupling. Maybe this can improve the performance with difficult RAM chips as experienced by MQ666. The ground planes on the main board are intersected on a lot of places by long traces. Ideally the loop formed by the VCC and GND wires of the RAM chips and the decoupling capacitor is as small as possible.

For example; the ground pins of C1, C4 and C7 are not directly connected to the gnd pins of the RAM chips they decouple. In their case it is only a matter of adding some stitching via's to the bottom layer or swapping them so that the VCC trace is on the other side. Same goes for C8, swapping C8 by 180 degrees would make the ground terminal connect directly to the ground terminal of RAM chip U3.

[PeteAU]

Originally Posted by Mathesar

This project is getting nicer and nicer (and popular it seems )

I had a look at the PCB layout again and I am wondering if we can improve the decoupling. Maybe this can improve the performance with difficult RAM chips as experienced by MQ666. The ground planes on the main board are intersected on a lot of places by long traces. Ideally the loop formed by the VCC and GND wires of the RAM chips and the decoupling capacitor is as small as possible.

For example; the ground pins of C1, C4 and C7 are not directly connected to the gnd pins of the RAM chips they decouple. In their case it is only a matter of adding some stitching via's to the bottom layer or swapping them so that the VCC trace is on the other side. Same goes for C8, swapping C8 by 180 degrees would make the ground terminal connect directly to the ground terminal of RAM chip U3.

These are good points. Do you want to make the changes or does clicking things in Eagle make you feel ill?

In the meantime I posted rev B.4 where I managed to remove 2 vias on the gary adapter by simpler routing, renamed C11 to R6 and put names "PeteAU, Mathesar, Mq666." on the back as credit.

Edit: I guess you are better at the analogue stuff, so I ask you. It kind of bothers me that U3 uses "the other VCC", do you think that's bad?

[Mq]

Hey, I don't think so I should be included in persons that contribute to project. I redrawed Mathesar's project only for my purposes. By the way I did it with bugs included:-) Next I found one small bug, and that's all what I did. I think deserving people are just PeteAU and Mathesar. You are the only authors of this wonderful project.
You can write my name if You want, but I think it's not necessary, and little strange:-)

Mathesar has right with ground and decoupling, I 100% agree.
And what You think about simplifying all the project? I think nobody needs to build this extension without Gary adapter. So maybe can You simplify the project by throw out the jumpers described "cut for Gary adapter"? And parallel jumpers for enable/switch? And some not needed elements like LED, so much parallel capacitors for example etc.
It's my subjective opinion only, but if I design schematics and PCBs, then I try to simplify them as much as possible.
And finally do not be angry:-), but I do not like the simultaneous placement of two RTCs. I understand it's all universal, but it makes some mess for me.

[Mathesar]

Originally Posted by PeteAU

These are good points. Do you want to make the changes or does clicking things in Eagle make you feel ill?

In the meantime I posted rev B.4 where I managed to remove 2 vias on the gary adapter by simpler routing, renamed C11 to R6 and put names "PeteAU, Mathesar, Mq666." on the back as credit.

Edit: I guess you are better at the analogue stuff, so I ask you. It kind of bothers me that U3 uses "the other VCC", do you think that's bad?

I don't think so. It may not look nice but as long as there is a properly routed decoupling cap there it will be fine.

I downloaded Eagle but I still find it difficult to use (type RIPUP @; to disable the copper pours? ). Improving the decoupling isn't much work I think. I can try but I think you can do it better!

I also think you deserve the most credit.
You know how it goes; starting a project like this is the most work. The rest of us just build upon your work.

[Mq]

I think Mathesar is equal right to be an author of Gary adapter. He designed it, tested, and it runs very good and accurate. We wouldn't have complete extension without his work.

[katarakt]

Originally Posted by PeteAU

The outline file is .GML and looks fine to me. The unrouted 19 is just some signals that we don't want to route from the main board to gary.
Go on, splash the $4.90+post and give it a go

Ups, sorry, i mean layer 20 "dimension" but it is correct now (in b2 it was not correct )

And yes, i'll order them for sure but with 1.6mm thickness....that's standard for all better boards. 1.2 is not good imho. As i want to order a few more boards i've to be sure to get the best working rev. ...thanks for b4 btw. . At the moment i have to finish some other little projects which have to be done at first, but after that i'm going to order the ram expansion.

This is absolutely a great project here. I think you guys are going to do a new optimized revision b5 ? ...amazing

[Mathesar]

Originally Posted by Mq666

I think Mathesar is equal right to be an author of Gary adapter. He designed it, tested, and it runs very good and accurate. We wouldn't have complete extension without his work.

I did a bug fix but Pete did all the heavy lifting.

Can we do it like this:

Original design by PeteAU
Additional logic by Mathesar
Additional artwork by mq666

[PeteAU]

All-right, Rev B.5 is posted (see 2nd post, first page).
Unless there's a major screw up, that's it for this year.
Let us know if you build it.

[Mq]

Good work PeteAU. Thank You.

[katarakt]

Thanks a lot

A new complete bom would be great for b5. Because it's a little bit confusing what have changed, what parts are used on new gary adapter and so on, this is not easy to figure exactly what parts are needed for people who hasn't designed the layout/boards.

What choice do we have now in b5 with RTC on the board and whats the recommended method ?

[PeteAU]

Originally Posted by katarakt

Thanks a lot

A new complete bom would be great for b5. Because it's a little bit confusing what have changed, what parts are used on new gary adapter and so on, this is not easy to figure exactly what parts are needed for people who hasn't designed the layout/boards.

What choice do we have now in b5 with RTC on the board and whats the recommended method ?

Maybe there'll be a B.6, Mathesar pointed out another thing, it never ends

The main board BOM is unchanged. I would recommend the RTC62421 (search AliExpress).
Just another 74HCT00 and 74HCT74 were added for Gary.

[Mq]

I use 74F00, 74F74 and 74F139. I tried HCT and it don't work properly.

[alenppc]

I just ordered some b5 pcbs, hope they work

[PeteAU]

Originally Posted by Mq666

I use 74F00, 74F74 and 74F139. I tried HCT and it don't work properly.

I successfully use: 74F00, 74HCT74 and 74F139. Seems strange they wouldn't work for you. Are you sure it wasn't "HC" by accident?

Originally Posted by alenppc

I just ordered some b5 pcbs, hope they work

Will be fine! It's a tiny change Mathesar suggested but won't affect function IMO.

[Mq]

It looks like extension randomly will work or will not work with the HCT. My friend tested 74HCT74, 74F74 and 74ACT74, and Gary adapter don't work with HCT for him. With ACT and F it works fine.
I think 74HCT is risky, so I solder 74F only, and I recomend to use F series, because F series has shorten propagation delay.

[katarakt]

Great info guys! Ok, b6 is coming...great

Alenppc, are you going to use 74F00, 74F74 and 74F139 ?

[alenppc]

Originally Posted by katarakt

Great info guys! Ok, b6 is coming...great

Alenppc, are you going to use 74F00, 74F74 and 74F139 ?

I am using SN74F00D, SN74F74D and MC74AC139DR2G

[kinmami]

Hello Guys
First of all congratulation for the project development and shared time.
I have written a BOM list draft where the highlighted items need your confirmation regarding the nominal value of some components and the suggested length of socket pins.
In attachment.
Thanks