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Monitor RS232 comms with millisecond resolution

It wasn't hard. I'm not certain anymore, but I believe I first heard about the information either in a magazine or through the materials received when purchasing. I do remember getting a price and part number to order from IBM, by phone, and then simply writing a check and mailing it off. It wasn't a lot of money, either. Especially considering that the IBM PC/AT, 6MHz and 20Mb hard drive, was priced at $5495, memory serving. If you could find a way to peal that much out of your wallet, the manuals weren't even on the radar scope.

My recollection is that the "lot of effort and money" amounted to about 1 day's effort (which I don't consider 'a lot') and the money wasn't even noticed. I didn't have to think longer than a few seconds, I believe. And when I received the material and the continuing supported updates to it, I only felt lucky that I'd taken the trouble. Never once thought about the expense of it. Must have been very small compared to the PC/AT cost, which itself was 'painful' enough to me. I am almost certain I might have not bothered, had the manual cost more than a couple hundred bucks. But I'm not sure, anymore. Just my 'sense' from memory.

When I wanted prototyping boards, the ONLY supplier ANYWHERE in the world that I could find was IBM. And I darned well knew I couldn't pony up the cost to hire a board house back then. Not then. They were WAY too expensive and my knowledge was near zero about ordering such a beast, anyway. I looked for alternatives, at the time, thinking that IBM had to be 'expensive' and that I might find less expensive alternatives. None existed that I could find. No one else had done it, yet. That came later.

And when they eventually did finally arrive (from Jameco?), they were obvious garbage. So I never looked back. There was no comparison.

I wasn't lucky, except for the fact that I was lucky that IBM cared enough to actually create something like this and sell it. There just wasn't anyone else around, so no choice and no luck. Anyone else actually looking and bothering to call IBM would have discovered the same thing I did, I think. They didn't hide the fact. They just didn't push it with advertising. You had to ask, that's all.

Anyone sensible should have been that diligent. I don't count myself special that way.

I've never hired out a single hour of time as an electronics engineer and don't believe I'd be competent enough to do so, either. Comprehensiveness is what is required for professional services and I can't deliver that. I know some things, but am terribly spotty elsewhere.

I started out as a hobbyist and that's what I imagine I am. 'Amateur' would work about as well as a word for it, though I'm not sure there is a difference that amounts to anything.

I'm a hobbyist. Honest.

This 'inaccessability' for even small professional companies is the center of my point. ISA is not only accessible to smaller professionals, but to hobbyists too. And wire-wrap _and_ sockets work nicely!!

Jon

Reply to
Jon Kirwan
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peel

... oh, well.

Jon

Reply to
Jon Kirwan

Active (must have been them, can't imagine where else I'd have got them then) sold boards with the appropriate edge connector and traces for typical interface chips -- then a huge wire-wrap area.

Personal Computer Technical Reference had full schematics for the PC side of the interface. Mine was off the shelf from a bookstore in Boston. Admitted, the farther from MIT, the harder they were to find. They were more scarce in Toronto.

And my first MIDI adaptor was a kit from a technically-aware hole in the wall called Computer Parts Galore.

Mel.

Reply to
Mel

I guess it is this more than anything else that puts ISA out of the range of hobbyists to my mind - you don't mess around with putting home-made cards into a $5500 computer unless you are happy to risk damaging it, or you are /very/ confident of your abilities. Either way, you are not a hobbyist.

Hobbyists who wanted to connect a card to a PC gave them an RS-232 interface or a parallel port connection - just like these days they give them a USB connection or an Ethernet port (or possibly a RS-232 connection).

Reply to
David Brown

That's a characteristic of those two particular boards. It's not a characteristic of ISA vs. PCI bus.

Replacing an SMT oscillator is really quite trivial. It's easier than replacing the non-socketed, through-hole parts on most ISA boards.

--
Grant Edwards               grant.b.edwards        Yow! ... the HIGHWAY is
                                  at               made out of LIME JELLO and
                              gmail.com            my HONDA is a barbequeued
                                                   OYSTER!  Yum!
Reply to
Grant Edwards

Which doesn't injur my point at all.

With good tools for SMT available. I recently _did_ after 30 years finally purchase my very first fine tip for attempting such work. But for 30 years, this would have been a disaster had I tried, while through hole is something I am quite long since used to handling.

Of course, none of this is about my earlier point regarding ISA vs PCI for hobbyists. Itself, of course, nothing about the earlier thread. So we are far out to field now.

Jon

Reply to
Jon Kirwan

Oh, cripes. I have nearly destroyed a _new_ $2,000 piece of equipment back around that time merely because I hadn't realized that the ground plug on one properly designed piece of test equipment I was using might cause a hot-side short to the IBM Model 85 electronic typewriter which didn't have such a plug and was plugged in reverse-wise. Nicely destroyed a power supply board, which I had to repair.

There is no question I was barely a hobbyist, if that, at the time. And yes, I was willing to take risks with my money because I wanted to learn, too. I did what I knew to do to avoid throwing money in the dumpster or killing myself, but I'm quite certain I didn't do as much as those smarter than me did. I made plenty of mistakes as I went. And I have had zero formal training here, by the way. Even to this day.

I don't know why you want to imagine I'm something I know I'm not. But there it is.

I used those, too. For example, in the above typewriter case I was scoping out the reed relay signals so that I could figure out how to turn it into a printer. I then designed and programmed by own 8031 board, with EPROM, and rat-nest wired the thing across the reed relays and brought out a ribbon cable to the tiny proto box I had. There, I used 1488 and 1489 level shifters with the 80C31 and a serial port to the PC for use as a printer. Worked first time (after fixing that power supply board in the electronic typewriter that I'd wrecked.) But this was almost around the same time when I also did my first proto board that plugged directly into that $5500 PC/AT. And I was barely any smarter at that point and nearly as likely to destroy something there, too.

You learn by screwing up and then reinforce the stuff you did learn well, by succeeding.

And I'm still a hobbyist.

Jon

Reply to
Jon Kirwan

It could if you're willing to change the crystal on the UART card...

Reply to
Fred

Yeah. I think that has been mentioned in this thread about... 20 times already?

And have you actually done this on a modern PC?

In any case, I haven't looked recently, but few PCs these days seem to sport RS-232 or RS-485 ports. For those that may, high integration on the board may not make it it so easy. I believe the ones old enough to actually have a south bridge probably use a super I/O chip or have it integrated into the south bridge along with the APIC and perhaps have some divider used to get the "pc standard" rates created. It all has to look like an ISA dohicky or old software won't work right. PCI boards also exist and they have drivers that are probably Windows-standard, too, but then that is a whole other thing to worry about and I'm not sure how the WinOldAp or NTVDM emulates the old chips into the DOS boxes.

It's been a long time since I looked, but unless I heard directly from someone who has achieved this with a new PC system, I'd be skeptical of a claim about it being easy to do.

Maybe someone has and can fill us in about it.

Jon

Reply to
Jon Kirwan

I only saw one other mention; somehow I missed the other 19.

Not on a PC motherboard, but I have done it on an expansion card.

Just the other day I bought a 2-port RS-232 PCI expansion card. Cost me $17 at a local retail store, but you can get the same card online for ~$12.

The card I just bought has a normal-looking, through-hole-mounted crystal on it. Even a software guy like me could swap it out.

Reply to
Fred

I believe I saw several different people mention the possibility and more still accepting the point and referring to it.

The comment of mine that you quoted was "I'm not sure an IBM PC uart can run at that rate." Note that I wasn't discussing expansion cards.

I wasn't discussing expansion cards.

I wasn't discussing expansion cards.

Jon

Reply to
Jon Kirwan

Yes, if you use the standard timer of MSDOS. But you can use an com1: read interrupt. To get 1ms resolution, all you need is a clock. I think, you could use com2: tx interrupt to increment a counter which could be used as a timer which is faster than 1/18,5 Hz.

Stefan

Reply to
Stefan Brröring

Why bother with the MSDOS clock ?

On most Pentium and later processors contained the 64 bit Time Stamp Counter register, which was incremented every clock cycle. You may have to find out what the actual CPU clock frequency was, but that should not be too hard.

Check availability of this counter and the availability of the RDTSC (ReaD Time Stamp Counter) instruction using the CPUID instruction.

Reply to
Paul Keinanen

Any PC since beginning till our days has 8253 (or compatible), clocked from 14.318MHz/12 ~ 1.193MHz. It can be used for the accurate time measurement. Leave channel#0 at the division ration of 65536 as it is, set channel#2 to 65535, don't touch channel#1 as it was used for memory refresh in the old times. You can measure time intervals up to an hour with the resolution of one tick of 1.193MHz. It works for any version of DOS up to Windows XP. Vista and Win7 won't let you into the ports.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

formatting link

Reply to
Vladimir Vassilevsky

Be warned: if you have a dual/multi-core machine, MS Windows does _not_ keep the TSC values of the cores synchronized. You have to lock to a single core the code that's reading the TSC if you want to get useful data.

--
Grant
Reply to
Grant Edwards

Sounds good. I am not so familiar with this type of programming on a pc. Its also a long time since i read technical documents about this. The trick with the com-tx int which was used as a timer, was about 25 years ago mentioned in an article in a german computer magazine (MC or C´t). There was also a description of the hardware components of a pc. I think, it was in May 1985 or so.

I only used the articles to write programs for the com-port under turbo-pascal at that times. Nowadays, i do microcontroller programming and a bit Delphi.

Best regards

Stefan

Reply to
Stefan Brröring

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