First CPU project, oscilloscope and more

[Goerofmuns]

Hello there!

I've been interested in electronics for a while, and I've done the whole Arduino and blinking LED things. I have decent programming background knowledge and I'm quite computer savvy. Electronics is great and all, but I wanted a more interesting project, then I came across the 6502 and the wonders it brings. I've been wanting to build a computer from scratch for a while now, and this seemed like the prefect thing. After reading quite a bit, I think I get the basics of memory, addressing, opcodes and assembly. I would like to get started as soon as possible, but I've came across a dilemma.

I have about 250 euros to spend on this, although I could do more. I have a good digital soldering Iron, and a small cheap Digital Multimeter, aaaannndddd thats about it. I see it looks like I will need an oscilloscope for this project, I've always wanted one and this seems like the perfect opportunity. However I don't know what to buy, there's analog and digital. I know the difference, but not whats best for me.

I live in a -reasonably- remote part of the world, I can get stuff shipped over, but there are no electronics shops over here. I know this is fine for components but for O-scopes I heard it would be good to buy local and get a warranty. I see many are going very cheap on ebay, is it a good Idea to buy a cheap old one and learn all the tricks of the trade on that? I've seen the Rigol 1102E recommended a lot but I've also heard that it's better to start analog, or have both. I've also seen those USB ones, although I personally would prefer an actual instrument.

Unfortunately it looks like I'll have to wait a few months until I can start on this project if I'm buying an O-scope. Oh well.

[GARTHWILSON]

Take a look at my 6502 primer on my website at http://wilsonminesco.com/6502primer/index.html, which has 22 chapters, one being on basic test equipment. At the moment the access seems to be extremely slow (whereas it should be around 100Mbps) but I'll have our son who does the technical part of maintaining it get right on it in the morning. I wish I had known half hour ago. He just went to bed.

[BigEd]

I thought there was a previous discussion somewhere here specifically about what order to buy equipment in, if you had a limited budget. But I can't find it. Archived version of Garth's page is here.

For sure there are people on this forum with very well-equipped labs, but also we've seen successful projects and successful diagnosis with little more than LEDs, critical thinking, and logical experimentation.

Ideally your multimeter has a frequency counting function. A logic probe is useful too (something which shows high, low, pulsing, oscillating states.)

If you don't have an oscilloscope, some types of problem will be harder to diagnose - but not impossible. Most problems are wiring trouble, power supply hookup, and noise on the power lines. So solid power wiring with appropriate decoupling gets a long way. You don't want high frequencies or over-fast edges, so don't go overboard on the fastest possible logic family.

A few previous discussions and debugging adventures:
- Beginner in digital circuitry
- Micro UK101 Build
- Recommended oscilloscope features?
- Cheap oscilloscope & other test equipment

Cheers
Ed

[Goerofmuns]

GARTHWILSON wrote:

Take a look at my 6502 primer on my website at http://wilsonminesco.com/6502primer/index.html, which has 22 chapters, one being on basic test equipment. At the moment the access seems to be extremely slow (whereas it should be around 100Mbps) but I'll have our son who does the technical part of maintaining it get right on it in the morning. I wish I had known half hour ago. He just went to bed.

Thanks! Access is too slow right now, what are you running? Linux server, or external hosting? I want to get an old desktop and make a file server with it, but I don't think my mum would be too happy with whirring fans constantly going under the stairs.....

[BigDumbDinosaur]

Goerofmuns wrote:

Hello there!

Welcome to our 6502 world.

Quote:

I live in a -reasonably- remote part of the world...

Where would that be?

[GARTHWILSON]

Goerofmuns wrote:

Thanks! Access is too slow right now, what are you running? Linux server, or external hosting? I want to get an old desktop and make a file server with it, but I don't think my mum would be too happy with whirring fans constantly going under the stairs.....

It's back up. He had to reboot the virtual server which is in NYC. The service costs only $5/month. He started out with an old PC (and we only run Linux) here in the garage which is a separate building, then went to a 1U rack-mount computer (which is pretty noisy) just for the purpose; but his own work was taking up more and more of the connection speed for VOIP and other things, and then my site was featured as "website of the day" by EEWeb last week so he moved it to a different service with connection speed over 100 times as fast as our upload speed. His own website and that of our professional-programmer daughter-in-law (wife of the other son), which get very little traffic, are still hosted in the garage. He has a great system of backups, so all the computers here get backed up to the server in the garage every night, and it has two 2TB hard discs and one gets backed up to the other, and then he has yet another backup for that in his room; and again the garage is a separate building, so it would be pretty hard for something like fire or theft to make us lose more than a day's work.

[Aslak3]

BigEd wrote:

For sure there are people on this forum with very well-equipped labs, but also we've seen successful projects and successful diagnosis with little more than LEDs, critical thinking, and logical experimentation.

Ideally your multimeter has a frequency counting function. A logic probe is useful too (something which shows high, low, pulsing, oscillating states.)

Seconded! My little 8 bit had life breathed into it with only a hacked up USB power supply, a cheap meter and a stack of data sheets. Skill, knowledge and rationale thinking can make up for many apiece of missing equipment. So don't let the lack of an oscilloscope deter you. The best tool you will ever have is your own intelegence.

Lawrence

[BigDumbDinosaur]

Aslak3 wrote:

BigEd wrote:

For sure there are people on this forum with very well-equipped labs, but also we've seen successful projects and successful diagnosis with little more than LEDs, critical thinking, and logical experimentation.

Ideally your multimeter has a frequency counting function. A logic probe is useful too (something which shows high, low, pulsing, oscillating states.)

Seconded! My little 8 bit had life breathed into it with only a hacked up USB power supply, a cheap meter and a stack of data sheets. Skill, knowledge and rationale thinking can make up for many apiece of missing equipment. So don't let the lack of an oscilloscope deter you. The best tool you will ever have is your own intelegence.

Lawrence

Yes, but a good logic probe sure eases the difficulty in troubleshooting a DOA circuit.

[Aslak3]

BigDumbDinosaur wrote:

Yes, but a good logic probe sure eases the difficulty in troubleshooting a DOA circuit.

Unless you mean something like a "super probe" (http://mondo-technology.com/super.html) I don't really see what a logic probe gets you that you can't find on a reasonably priced MM. Eg my VC97 was about 20UKP. It has pulse counting etc. the only thing missing is the sounder, but... Really? I will some day make my own one, of my own design, but more for fun then actual use.

[APL]

Goerofmuns wrote:

I've seen the Rigol 1102E recommended a lot bu

I picked up a Tektronix TDS 210 on ebay it's small and compact which serves my purposes perfectly well. A programmer is a must, I see some folk have built their own. I used to have a uv eraser for the old 27 series ROMs, but I'm currently using 28 series Amtel EEPROMS.

If you are comfortable with electronics, then it's very likely you can build your circuit and get it working with just a multimeter alone. I like a scope, 'cos you can see the waveforms and tell if a chip is being accessed. So long as you are cautious with the build, I don't think one is necessary.

Something as simple as an 8bit latch and eight leds or two til311 latched to the data bus, can give you a great deal of confidence that your basic system is working.

[GARTHWILSON]

I frequently use an oscilloscope for debugging software, for example pulsing an output pin every time the program counter reaches a particular place in the software, in realtime applications that cannot be slowed down or stopped for viewing something. With two inputs, you can have a pair of these and use one to sync to for example, to visually frame a set of pulses on the other. Old 20MHz analog 'scopes can often be found for free. One of mine was.

[BigDumbDinosaur]

Aslak3 wrote:

BigDumbDinosaur wrote:

Yes, but a good logic probe sure eases the difficulty in troubleshooting a DOA circuit.

Unless you mean something like a "super probe" (http://mondo-technology.com/super.html) I don't really see what a logic probe gets you that you can't find on a reasonably priced MM. Eg my VC97 was about 20UKP. It has pulse counting etc. the only thing missing is the sounder, but... Really? I will some day make my own one, of my own design, but more for fun then actual use.

I have a fairly basic BK Precision DP-21 logic probe that I purchased nearly 25 years ago that is convenient, easy to use, trustworthy up to 20 MHz, works with TTL and CMOS, and requires no programming like the aforementioned "super probe." All it needs is a source of power and a circuit to test. I've yet to see any multimeter that is as good as a logic probe in troubleshooting high speed digital circuits. The DP-21 was all I needed to debug POC V1.0 when it didn't work right at first try.

I also have an H-P 275 MHz 'scope that doesn't get as much use as the logic probe. Go figure!

[Goerofmuns]

Woah. So many replies in one night. I always love an active forum. So I think I'll put off the O-Scope for now, maybe when I move, but I'll probably add a logic analyzer to my mouser basket. I'm also making a Binary-to-Hexadecimal thing with the Atmega from my Arduino Uno, HexOut style. That should help with addresses and the like, also I need something to do while I wait for parts .

[GARTHWILSON]

Goerofmuns wrote:

Woah. So many replies in one night. I always love an active forum.

<thumbs up>

Quote:

So I think I'll put off the O-Scope for now, maybe when I move, but I'll probably add a logic analyzer to my mouser basket.

Errr... make that "logic probe." Here's a logic analyzer, the Agilent 16821A 34-Channel Portable Logic Analyzer, kind of a low-end one, at $26,000 starting price:

[Goerofmuns]

Quote:

Here's a logic analyzer, the Agilent 16821A 34-Channel Portable Logic Analyzer, kind of a low-end one, at $26,000 starting price:

AgilentLogicAnalyzer.jpg

Oops. I meant logic probe, thanks.