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SBC interest?

S

scorch

Member
Joined
Apr 17, 2009
Messages
32
Location
Sierra Mts, CA
I was wondering if there might be any interest in creating a single board computer (SBC) that is basically VC forum designed and supported? I know there was a project recently by lynchaj, but that was a sorta preconceived Z80 CPM type widget. What I am talking about here is creating the ideal SBC with all the best features based on input from our VC users. Many guys here have experimented with various SBC's such as the good old KIM-1 and others. While those are fun to play with from a nostalgic point of view (I myself have a KIM), most use old technology and outdated ideas. A new SBC incorporating modern technology, software, and features would be fun to build and use, user friendly, and an excellent training tool for those who might like to understand things at a lower level. We have a lot of talent here, let's see what we can do by putting our heads together.

Ask yourself what your own personal SBC would be? Things should come to mind like... data bus size, CPU(s), display, memory, I/O, power supply, etc. Bear in mind the balance of modern technology vs user friendly features and ease of use. For instance, a modern P4 or AMD dual core might be powerful, but attempting to learn those CPUs at a machine level could be a daunting task; especially for newbs.

I think this would be a fun project and everyone interested, regardless of skills, could find a way to participate. If you don't have hardware or software experience, there may other things you could contribute like user documentation, debug history regression, archiving, burning ROMs/CDs, etc., so the project could be divided up into tasks and action items, appropriate to skill sets. Like with other projects here, in the end we should have created a PC board and kit of parts available for group purchase for those who want to build it and play.

To start things out, some cool features might be...

Hardware:
8 bit CPU (Z80, 6809, etc.)
Small graphic LCD
USB port
VGA output
SD or CF card interface
Hi current driver port(s) for LEDs, relays, etc.
Timers with interrupt capability
Motor controller for small DC or stepper
Hex keypad
PS2 KB connector
Small prototyping area or breadboard
PWM speaker
A/D & D/A interface
EPROM/EEPROM/FLASH programming socket
Simple wall wart power supply

Software/firmware:
Updateable flash ROM with low level monitor proggie
Full breakpoint debugger
Mini assembler (no, this is not a midget with a soldering iron)
Single step capability showing full register dumps
Upload/download from PC

Hopefully, I left room for others - LOL. When "blue sky" thinking, try to keep an open mind about the possibilities of other uses for the SBC, such as robots, or other machine control. It's important at this stage that no idea is dumb or stupid, so just throw anything on the table, even if it seems impracticable, too costly, or too difficult. We can weed out features that can't be done later. Often it's the inexperienced minds that come up with the best ideas because they are not preconditioned.
 
Most of those features are already incorporated in the N8VEM, or available via it's expansion bus(es). It's not a limited single-purpose (CP/M) widget, but rather a very versatile design with many as-yet untapped possibilities. (It's just kewl that it's also a full-blown microcomputer, ready to run right out of the box as well).

/completely voluntary, unsolicited, unpaid, and impartial plug

--T
 
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Cool. I like building SBCs.

The N8VEM is open source which means every piece of software is free and every part of the hardware design is available. You can buy a board. Or download the design and get your own made. Parts are available from multiple sources. As a result it has gone off in all sorts of directions. Andrew Lynch has built hard drive interfaces, floppy interfaces, a 6809 chip, S100 bus etc. I've gone off and built 5 versions of the board, all building on the previous one. This was an incarnation a few months ago http://hackaday.com/tag/n8vem/ and the next project is getting mass storage via sd cards.

I think I could say 'check' to more than half the things on that list.

Picaxe and Arduino are perfect for the interfaces - eg if you want a smart multi analog input to RS232 adaptor, or you want to drive many servos then they are great. The only problem I have found with Picaxe and Arduino is I kept running out of code space. At least the N8VEM will never run out - 64k of space (vs 0.256k for the smallest picaxe), 448k of battery backed disk ram and (soon) 2 gig of sd.

I like the N8VEM because you are not tied to one language. C programmers do Arduino. Basic programmers do Picaxe. The N8VEM can do C, Basic (many dialects), Fortran and about 10 others.

If you want VGA - check out the PockeTerm on the Propeller. Indeed, the propeller guys have a Z80 emulation running now and are close to getting an entire Z80 machine onto a PCB 1/4 the size of the N8VEM.

We have had demonstrations of wireless networks and internet access too and are very close to pulling it all into one working system.

Things like step by step debuggers with register dumps - I know what you are saying because I have just spent the morning using one. A great way to exercise the brain!

I suppose one question to ask; which things on your list *can't* be done with an existing board? And what would it take to add the feature? Is this a teaching tool or something with a use already in mind?
 
Hello Scorch,

Been there, not done that....been there, not done that, been there.......

The subject has been discussed in numerous occasions on various
forums, and it has rarely been realised. My motto in VC forum
has always been "If it works, stick with it!". It has taken many
years to have few very dedicated and knowledgeable people to
come by and build it from the bottom to the top.

>If you don't have hardware or software experience, there may other
> things you could contribute like user documentation, debug history
>regression, archiving,....

If you are one of those who would like to do it, there is so much work
that can be done in the "documentation" department for N8VEM. Your
efforts would be highly valuable for educational purposes to a wider
audience.

Keep your feet on the ground and reach for the stars....:)

Best Regards

ziloo
 
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Best Regards

Best Regards

Hello Scorch,

Looking at my post again, I realised it was a bit imposing and
critical. I had to edit some of my wordings to sound the way
I intended them to be. I hope they did not cause any hard
feelings. Your enthusiasm and knowledge is the most valuable
asset for any group that you work with. I just wish you would
join other comrades to utilise your knowledge and experience in
improving the work in progress.

Sincerely,

ziloo
 
I like the idea of putting energy into the N8VEM rather than starting a new project. The added benefit is that if you're going to make something at least remotely like the N8VEM, you might as well take that one apart. There's more to just the board. There's chip cost, production runs, etc.
 
I must admit that the N8VEM is probably not all that well explained on the website - if you go to the forum you get the latest discussion this last week, and if you go to the wiki you get a pile of files but it is hard to work out what is actually out there. I like it because it is totally open source. There is nothing wrong with adding your own board of any design and if you interface it in some way to the existing boards you can add it to the project. I think there is a bit of cross fertilization to this forum anyway. The N8VEM is still vintage - vintage software, new board (but often vintage chips!)

Hardware:
Yes to both: 8 bit CPU (Z80, 6809, etc.)
Yes: Small graphic LCD
No: USB port
Yes: VGA output
Almost: SD or CF card interface
Yes: Hi current driver port(s) for LEDs, relays, etc.
Yes: Timers with interrupt capability
No but easy with picaxe: Motor controller for small DC or stepper
No but easy: Hex keypad
Yes: PS2 KB connector
No: Small prototyping area or breadboard
Yes on PockeTerm: PWM speaker
Yes via picaxe: A/D & D/A interface
Yes to eprom/eeprom: EPROM/EEPROM/FLASH programming socket
Yes: Simple wall wart power supply

Software/firmware:
Yes to eprom: Updateable flash ROM with low level monitor proggie
Yes (DDT/DDTZ): Full breakpoint debugger
Yes (TASM/ASM/M80): Mini assembler (no, this is not a midget with a soldering iron)
Yes (DDT/DDTZ): Single step capability showing full register dumps
Yes (38400 baud with xmodem): Upload/download from PC
 
The N8VEM is sort of cool and all but, actual z80 boxes are cheaper and a whole lot more atheistically pleasing. That is a personal taste thing of course.

I mean if you want to enjoy building up your SBC its cool but, if your just after cp/m or a z80 you can pick up an old Osborne for less then the N8VEM alone will cost you to build not even slightly counting the terminal or those add on projects. Of course for other processors there really aren't a lot of choices. Just a ton of cheap z80 boxes around in the US anyway. Seems a bit like reinventing the wheel.

Zilog sells their development kits for like almost nothing as well as was pointed earlier. Look what you can get for $99 http://www.digikey.com/scripts/dksearch/dksus.dll?Detail&name=269-4560-ND
 
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That was my point. In particular that $99 kit has:
  • Up to 2MB fast SRAM (12ns access time; 1MB factory-
    installed, with 512KB on module, 512KB on platform)
  • Embedded modem socket with a U.S. telephone line interface
  • I²C EEPROM
  • I²C Configuration register
  • GPIO, Logic circuit, memory headers
  • LEDs, including a 7x5 matrix
  • 2 RS232 ports
  • RS485 connector with cable
  • JTAG debug interface
  • 50 MHz (!) EZ80F91 with 256K of internal flash and 8 KB of internal SRAM
  • 512K of SRAM
  • Space for 1MB Flash
  • Ethernet
  • IrDA port
  • Clock with battery backup
  • Development kit software
Okay, it doesn't have USB, but I'm sure there's an eZ80 development board that does.

A heckuva deal.
 
In the words of comedian Jim Carrey... "well alrighty then". Frankly, I'm a little surprised and disappointed about the overall negativity expressed here, but after some re-examination, I've concluded that VC is really not the right venue for this project anyway. For the folks who said this has already been done, or that you can buy an evaluation board; kudos - you are absolutely correct! Fact is, except for perhaps, Dr Acula, it appears that most missed the point altogether, or else I did a poor job of describing it properly (which wouldn't be a first - LOL). The true goals of the project in order of priority were...

1st: LEARNING - CPUs, memory, I/O, and interfacing logic at the bit and byte level
2nd: PARTICIPATION - bragging rights as a team member and having a say in the final product
3rd: FUN FUN FUN playing with a real widget that each of us helped create

To some experienced engineers, this may seem a ho-hum project, but these are always the most fun for me (BTW, I have an MSEE and 20+ years experience at a Sr Engineering level). I did have hopes that less experienced members would find it appealing and challenging. To wit, I noticed several in the N8VEM dialog who seemed to want to participate, but didn't appear to have the opportunity. In all honesty, I have to admit and somewhat selfishly, this project was not so much about VC forum members as my high school kids. After having come off our mildly successful last project (yes, we have money in the bank), we are set to launch our next. For this one we thought it might be fun to go outside and solicit broader user input on the design. This is why I attempted to expand the project to the VC forum. I now think it was a bad idea, based on the forum's charter (and responses!). As a result, I discussed it with my students today and have decided to pull the project back in. We will be doing it as another internal classroom project, so perhaps the lack of enthusiasm here will have a positive outcome in the end.

Terry Yager said:
Most of those features are already incorporated in the N8VEM, or available via it's expansion bus(es). It's not a limited single-purpose (CP/M) widget, but rather a very versatile design with many as-yet untapped possibilities. --T
Click to expand...

Agreed, and a few of the reasons why I wouldn't consider it for this project. I never said the N8VEM was limited or single purpose, I said it was a "preconceived Z80 CPM type widget". Permit me to explain... it was preconceived because, according to Andrew, it was lifted from something he was already working on. It was CPM oriented, because Andrew stated as much in the forums. However, I was not implying that it's not a super product! Its direction and context were simply wrong for what I had in mind. So for the record, I didn't mean to slight the accomplishment of the N8VEM product, and I certainly didn't mean to step on any toes.
 
Oh, I don't think you stepped on any toes or denigrated the N8VEM in any way, but I think you might have gotten some different replies if you'd explained a little more what you had in mind. As it was, to suggest designing just another generic SBC from scratch when there are already so many out there (most of them flexible enough to be whatever you want them to be), understandably didn't raise much excitement. The basic CPU/memory/IO stuff is pretty standard and straightforward, so why reinvent the wheel once again; what's interesting and fun for most people is the custom ancillary stuff "around" the basics and of course the software. Fancy displays, wireless comm, internet connectivity, real-world control and data logging etc. And of course being compatible with an existing OS like CP/M means that you can use BASIC and standard tools to manipulate your board (if you want to) and it can actually be useful instead of just a 'project' that blinks a few lights and ends up in a drawer.

If designing from scratch, laying out PCBs and having them manufactured, etc. are important to you then obviously existing designs and boards aren't very interesting. But if you read through the N8VEM forum and see the problems being solved, the individual innovations and especially the sense of community I think you'd have to agree that there's certainly a lot of LEARNING, PARTICIPATION and FUN FUN FUN happening there and it's going to be pretty tough for you to find interested people here or on any forum who aren't already involved with one of the homebrew projects, to essentially create the same kind of community around yet another SBC project. Although Andrew has certainly been the prime mover behind the N8VEM, it has nevertheless been and still is being largely shaped by the builders, with some creating related semi-compatible boards on their own and of course contributing those to the group as well as their software, tools etc.

That's one of the fun things about the N8VEM: everybody's part of the same "club" and working with more or less the same hardware, but in fact every system is unique and very personalized and the different ideas and executions feed each other; more like a biological system than a bunch of computer clones.

Even if you do go off on your own, your students might enjoy just reading the N8VEM wiki and what the various builders are doing with them in the Google forum.

Whatever you do, have FUN, FUN, FUN! And if you do come up with a design and boards, why not come back here and tell us about it; once it's "off the ground" you might find a little more interest.

mike
 
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Okay, if it's to be an educational project, I can understand.

But why sidetrack the learning with a lot of make-work (e.g. adding buffers, transceivers or decoders to a 70's era CPU?). If sweating the small stuff is that important, then retreat back to an 8080A or figure out how to make refresh work for TMS4096 DRAMs. My own recommendation to Andrew was to move up a decade and make use of a Z180/HD64180 or even a Z280. Solves so many annoying little problems.

I recall that the least fun stuff was thw "small stuff", like running the numbers on an 8202 DRAM controller driving 2116s and discovering that worst-case, your DRAM has to have a negative access time. Or wondering what idiot designed the 8275 CRTC.

If I wanted to work "from the chips", I'd take a relatively modern uC, such as an ATMega and work from there. All of the nasty stuff is out of the way for you to do some real experimenting--and the chip's cheap and very forgiving. If it's a matter of running vintage software, I suspect an ATMega 128 could easily emulate a 2MHz Z80 without breaking a sweat.

But that's me. :)
 
I totally get the desire behind it but, it seems wasted. The idea behind the homebrew computer scene has usually been about better or cheaper. In the best case better and cheaper. At the very least the same. The whole N8VEM thing seems worse and more expensive then just about everything else available. I mean if the N8VEM cost $20 complete then sure but, that just gets you an empty N8VEM circuit board. Seriously ?
 
No "stepping on toes" going on here! This is healthy debate and who knows where it might go. We have Chuck's comments, then leaknoil's link and that lead me to googling the ez80 and to this site http://www.ez80sbc.com/Download/eZ80SBC Installation Guide.pdf

That is one nifty board. And it appears it can run cp/m 2.2 and cp/m 3. I might check it out further.

I reckon I can make a N8VEM for about $50. I can make boards for $4, and indeed, to anyone who shows even just the mildest of interest on the N8VEM group, I've been giving them away for free. Or less than cost. Usually just with a request to contribute something in kind. I think one of the keys to this project has been Andrew Lynch's insistance on using standard DIP parts. This gives the board an "old fashioned" look and perhaps that is off-putting to some. I spent much of my youth building little boards to go in model planes where smaller=better. I've done my time soldering tiny components *grin*. What I have now realised is that there is plenty of space on the planet for a slightly bigger board. I've realised that allowing for mistakes, solder blobs, mysterious shorts, I can solder a DIP part faster than a surface mount part. And I have another motivation - in order to solder surface mount, I have to go off coffee and beer for several days...

Anyway, if you want something for high school kids, maybe look at Arduino or Picaxe. $4 chips, programmable in C or Basic and only a few minutes with a breadboard and you can have a led flashing. Then read a pot, display something and the kids will be unstoppable. There are a lot of educators and teachers over at the Picaxe forum for instance and they talk about the practicalities of teaching microcontrollers, like whether the school budget can afford a set of batteries for every student, let alone a micro. Breadboards are cheap nowadays, and a small picaxe solderable board can be made for under $2. So nothing lost if the kids turn out not to be interested.

I'm having fun fun fun today. Using input from many people, we have managed to create a system where you can write a big (10k-30k) program, hit a "compile" button and have it running on a board in only 5 seconds. That is quicker than anything the Picaxe and Arduino can do, and may even be quicker than the propeller. For me, fast compiles = fun, because you can test things quickly.

Sing out if you want to brainstorm boards etc.
 
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scorch said:
... "well alrighty then". Frankly, I'm a little surprised ....
Click to expand...

All that is said here is right on the topic, and all that I heard is
appropriate and justifiable. As I said, the same kind of argument
and brainstorming had been going on for a long time on various forums,
and each one of the argumenters had a good point about what
should be on an SBC. They were all right!!!

There is no saying "which is the best SBC to build" , it is a
matter of "build the &^%$#*(!@ thing, no matter what!"
Andrew was one of those who just decided to start building what
he thought was the best design for its purpose. Now that he has
started building an S-100 board, there are people who are criticizing
him as to "why he even dared to think about building one, while
there are so many old S-100 boards still around"!!!

What I would very much like to see here personally is a critical
review of the harware/software capabilities of the N8VEM and any
modifications/peripherals/software enhancement that they think can
improve its performance. I am talking real physical work, that
I can compare and see the results, not just verbal suggestions.

I think the starting point is to "actually build an N8VEM and test its
performance" and start making changes as found necessary.

ziloo
 
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scorch said:
..... I have an MSEE and 20+ years experience at a Sr Engineering level).
I did have hopes that less experienced members would
find it appealing and challenging....
Click to expand...

Now that we know about your passion and expertise, we would not
let go of you that easily! We have been waiting for a long time to
have more hardware oriented people among our VC forum members.
Although we have a wealth of VC enthusiasts that truely go out of
their way to help others, and they know a lot about various aspects of
hardware/software troubleshooting, we also need more people at the
solder level!

If you can start a column/thread about "How to Troubleshoot a
Dead Computer" (just an example), you would be a star! Things like
the fundamentals of O-scope and how to use it, how to use a voltmeter,
where to start, and some step by step guidelines; there would be more
people who would join in, and it would be a blast. These are just a few
suggestions and you can apply your own interests. Give it a try, and
check out the number of hits/viewers that would be reading your thread!!!!

ziloo
 
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leaknoil said:
I totally get the desire behind it but, it seems wasted. The idea behind the homebrew computer scene has usually been about better or cheaper. In the best case better and cheaper. At the very least the same. The whole N8VEM thing seems worse and more expensive then just about everything else available. I mean if the N8VEM cost $20 complete then sure but, that just gets you an empty N8VEM circuit board. Seriously ?
Click to expand...
I think you're missing the main point, that it's about having FUN!, and cost is relatively unimportant. You might as well just pick up a used complete CP/M system on eBay for $50 if that's what you're looking for, or even a PC MoBo from a curbside box..

m
 
MikeS said:
I think you're missing the main point, that it's about having FUN!,
Click to expand...

Actually that's why I specifically wrote that I understood the desire to build something like this. I just don't know that the world really needs yet another z80 based SBC. By all means go for it though. It just seems maybe the effort could be better spent on something there aren't already so many of out there.
 
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