Keyboard Design for 8-Bit Computers

This is a short video dealing with the design process of a Keyboard Matrix for 8-Bit Computers.  I talk about some of the hardware design principals as well as software considerations.  More of a VLOG style post than anything.  But worth a watch if you’re into this sorta thing.

ELM Programmer PCBs Available

Now that the boards are verified to work as intended, I have added the boards to the shop. There is also a zip file available for download on the product page that includes a Bill of Materials, documentation for building the board, as well as the required software to use this board.  Remember, you must have a DOS computer with a parallel port in order to use this programmer.

The PCBs are available here.

PLD Plague – Problem Solved!

The G80-S has been plagued by the simplicity of it’s design.  The use of a single PLD to do all of the onboard decoding has led to an unusual issue.  One where the Programmer of choice is apparently selective concerning which PLDs it decides to program.

Thats right, it appears that the MiniPro Programmer just doesn’t like GAL22V10 PLDs.  I do not know why.  All I know is that some variants work without any issue. Some will not program at all.  While others have intermittent programming problems.  The interesting part is that I have not experienced this with any variants of the GAL16V8.

The solution to this issue has been to build a new programmer.  Luckily for me, there was a gentleman in Japan who took this task upon himself almost 20 years ago and created the ELM programmer and accompanying software.  See that information here:  ELM Gal Programmer.

Some time back there was another gentleman with the N8VEM project that decided to take the ELM programmer’s schematic, and create a PCB.  And then some time later I found the project and ordered a batch of boards.  And as a result of that brief history, I can now program GAL22V10s of any variety (not Atmel parts) with only some small modifications to the WinCUPL JEDECs (The software appears to not like all of the documentation in the JEDEC files).

The software requires a DOS computer with a parallel port.  Here I am using my Halikan LA-5040, a portable 386 machine with 5mb of memory and a monochrome LCD (or VGA out).  Here you can see the dump of the contents of one of the G80-S Micro’s PLDs.  It works!

So what does this mean, you ask?  Well, it means that we can finally start stocking the G80-S PCBs with the PLDs again!  Stock will be adjusted tonight to account for the additional availability.  Also, at least temporarily, we will be offering some of the ELM Programmer PCBs on the store.  However, we will likely be offering a variant of our own design (simplification of parts) in the near future.  Those PCBs will be added to the store as soon as I get a chance to add them.

Upcoming Review – JLCPCB

I was recently pointed to the Fab House JLCPCB, which is another cheap PCB fabricating service out of China. Seeing as they have some really good deals on their website I decided to order a batch of PCBs for review.

Typically I order my PCBs from Elecrow (a service that deserves its own review, I really love this company). But I think a side by side comparison would be beneficial. And as such, I will be doing this as soon as the boards come in. They’re currently being finished and will be shipped via the 2-Day DHL service. But, it would appear that they have made a mistake, as they started over in the production, they have a time stamped log of the boards as they’re being produced. It will be interesting to note the quality of the boards versus the Elecrow boards.

I had hoped to have the boards by this weekend. But, it looks as though I will have to wait until next week. As soon as I get the boards in the mail I will get pictures, and start comparing the two services.

Community Group on Facebook

Thats right!  First it was a Facebook Page, now we have set up a community group!

The idea behind this Group, as well as the Page, is to initiate more dialog between fans of the Website, YouTube Channel, and owners of the G80-S Micro.  Really!  I like talking to others who have the same interests!  I’ve called members at their request and talked them through problems with their computers.  I’ve help others port software over to computers of their own design.  And I have helped with all types of requests via email.  I truly enjoy having so many great people to support and follow my experience in electronics and vintage computing.  If not for you, this site would not exist.

And because of that, I want to talk more about projects, interests, and electronics.  And I want to invite you all to talk with each other about your interests!  And that is the intent of the Facebook Page and Group.

Below is a link.  But if for some reason the link eventually dies, just look for the RetroDepot.net Page on Facebook, and the group is added to it’s menu.  I look forward to talking to you all!

RetroDepot Community

RetroDepot is on Facebook

RetroDepot has joined FB! While this will be more of a ‘this is what is currently happening’ type account, meant to share the day to day activities rather than the formal posts on the website, I thought it would be a good idea to build a community. One where others can comment, share their own projects, and participate with others of like minds. The link is below, enjoy!

https://m.facebook.com/retrodepot.net/

Problematic PLDs – The Answer is Near…

The problem that I have been having with PLDs in the recent past may be close to being resolved.  The last few times that I’ve ordered GAL22V10s from any source my programmer, a TL866 (aka:  MiniPro), has been unable to program them. Considering that my G80-S Computer requires this PLD for it’s decoding logic, and that many users do not have a means to program these chips, this creates quite a problem.  So I have set out on a quest to see if the problem with the over 120 GAL22V10s that I have have in my possession is truly a problem with the ICs, or if it is an issue with the programmer.  I suspect the second is the cause.

So, I have ordered a batch of boards for the ‘ELM Simple GAL Programmer‘ and have built one to test.  Above is the board.  The person who designed the board used a Male to Male 24-Pin Serial Cable for some reason, rather than a proper Parallel Cable.  I do not know why.  But Since I do not own a 24-Pin Male to Male cable, I’m waiting on one to arrive.  The rest of the board is done.  I’ve already applied voltage and test the VCC and the 15v lines, and adjusted them to their proper voltages.

Assuming this works for programming the 22v10s that I’ve had so many problems with, I will likely redesign this board so that it is a little more proper, and then offer it in the RetroDepot store.  However, I will likely sell off the extra boards that I ordered once I confirm they do in fact work.  Until then, no sense in selling PCBs that I’m unsure of.

N8VEM SBC V2 – Still awaiting shipment

Well, Mouser managed to send an email today letting me know that they have shipped my package which has the needed parts to get this board up and running. However, it looks like the package will not get to me until 1/13/18 (4 more days).  Even though I am only 4:30hrs away from their warehouse.  I’m going to be honest, I’m not very happy with their service this time around.  But I suppose every company is allowed to have a bad day from time to time…

I already have all of the sockets and passive components soldered. I’m just waiting on the chips to stick into the sockets.  As well as an oscillator. I plan on testing this board at 16mhz , but may drop the speed depending on how the initial testing goes.  I decided to go with ACT logic families, since they have a very fast propagation delay, low power consumption, and are CMOS and TTL compatible.


The bare SBC V2 Board


Missing only the chips, the CPU Clock, and a 1k resistor array (RR1).  Well, and it needs a bi-color LED…

I actually had several of the chips needed on hand.  The board currently has a 20mhz CPU (z80 of course), an 8255, an 16C550, and a MAX232CPE.  But I still need to have a few more ICs before this will be able to boot to CP/M.  Still waiting on Mouser…

As you may have noticed in the second picture above, I installed a machine pin DIP-8 socket in place of P4 (CPU Clock).  This allows me to try a variety of oscillators until I find one that works as desired.  The goal is to have a very fast processor, and be able to run the SCG (Sprints and Color Graphics) Card in this computer.  Though I hear that card prefers something in the range of 4mhz.  For some reason I have to believe it can handle more speed.  Maybe the person who suggest this used a slower logic family???

As soon as I have more to report I’ll be back with another post.

Website Update, and Other News…

It’s been a while since I have been able to update the website.  That has mostly been due to the holidays, but also general problems of being an adult, like work…

But, fear not. I have managed to make a few updates this evening.  There is now a downloads section available by using the main menu at the top of the site.  Also, I’ve added tabs for Links, as well as condensed the Store into a tab where the cart and the checkout can be accessed.

I’ve worked on the downloads page to the point that I think it is functional.  It looks ugly to me, but it serves it’s purpose.  Maybe I need some nifty graphics or something…

I’ve got to finish working on the TinyBASIC source.  It has been brought to my attention that there is another issue with it, although it is not something that I have toyed with.  So I’m not sure where it went broken.  The average user will probably not notice it, but if you are trying to use programs found on the web, you may run into problems were it concerns the syntax.

I received a batch of boards for the N8VEM SBC V2, and some Harlequin 48k boards.  I may be offering some of those in the store before long.  I would like to build them first to make sure the boards came out as expected.

I am working on building a N8VEM SBC V2.  I am currently waiting on parts from Mouser.  Their website said that the parts would leave their warehouse 3:30hrs after I ordered 3 days ago, and I received an email this morning stating that they would likely be shipped today. And, they would send me an email when they had shipped.  It’s now 9:30pm and that email has not arrived.  Broken promises….  But I’ll get a blog post, maybe a video, of that up as soon as it’s complete.  I also have an 8-slot ECB backplane on the way from John Coffman.  It’s the 167mm version of that board, so I am really looking forward to getting this setup.  I plan on putting this system into a 19″ 5U rack mount enclosure.  Along with a front panel that displays address, data, and status lights.  I am thinking something along the lines of the Magic-1 as seen here:  http://www.homebrewcpu.com/

I’m also, as we speak, printing up an enclosure for my N8VEM Zeta SBC V2, and the ParPortProp board.  Thats more of a work in progress.  But I may get a few pictures up as soon as it looks halfway decent.  I’m no artist, especially when it concerns 3D objects.  But I try.

So here is to making 2018 a great year!!!