New homebrew repair/troubleshooting tools

DogP

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So... after years of plans, but lack of motivation, I've finally gotten around to building and programming some (hopefully useful) tools for myself. First of all, I've had a portable 32 channel USB logic analyzer (Bugblat X34 - http://www.bugblat.com/products/x34.html ) for a while, which claimed to have a programming API, but no real documentation on using it. So I finally decided to sit down and figure it out.

Once I figured out how to use it, I decided to make a 32 channel logic probe. This allows me to connect it to an IC clip, then see the activity of all pins on the chip at once. Much quicker and easier than probing each pin with a normal logic probe.
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The next logical step was to add some intelligence... actually verifying that the pins are valid for the type of chip being probed. Essentially, a simple logic comparator (though it only works for chips without memory or states).
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Mostly because I'm lazy, these apps are all simple console apps. Maybe someday I'll actually make something better... but I really just wanted something quick that works.


And then I had another project idea... after blowing lots of fuses working on stuff (especially monitors), I thought it'd be nice to just use circuit breakers. But finding circuit breakers for every size fuse would be tough, and expensive... so I drew up schematics for a programmable one. I realized that it wouldn't really be that tough, so I went ahead and built it.
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Basically, it's got a current sensor, ADC, and relay connected to a microcontroller with controls/display. Just connect it in place of the fuse, set the desired current, enable it, then see what happens. It shows the current draw in real time (basically an ammeter)... and I put a fuse holder in line, so you can fuse it with the proper fuse, in case something fails. But the "breaker" should save the fuse.

And while I had the microcontroller in a convenient portable enclosure, there was very little effort needed to also create a monitor signal generator. So, I used a 3-way switch to either run in circuit breaker mode, or monitor mode. As a signal generator, it can create CGA, EGA, or VGA signals with seperate or composite sync. It'll soon be able to do positive or negative sync, once I tweak the code.
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I'm also working on adding XY to the monitor tester... hopefully my chips will arrive soon. :) The whole thing runs off a 9V battery. I'll probably work to optimize the battery consumption once I get everything finalized.

Anyway, there's a quick rundown of my new tools. They're not completely finished... I mostly have some testing to make sure they all work as well as I want them to... as well as more coding, and refining things a bit. But I just thought I'd share what I've been up to lately... hopefully some of you find it interesting.

DogP
 

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I would be very interested in the selectable fuse / pattern generator if you think about producing some.

If you were to lean one way or the other and drop one of the functions I for one would love to have a neat and clean pattern generator in a small form factor case....especially if you add XY.
 
That logic probe is great, it's more along the lines of what I'd hoped for when I bought my HP. The HP works, it's just that there is so much hassle switching everything between chip types.
 
Thanks for the compliments!

I would be very interested in the selectable fuse / pattern generator if you think about producing some.

If you were to lean one way or the other and drop one of the functions I for one would love to have a neat and clean pattern generator in a small form factor case....especially if you add XY.
Yeah, I don't imagine that too many people are itching to get a programmable fuse. I wasn't even able to find any mention of anything like it (for sale or otherwise) on the internet... but I guess the ability to make stuff when you can't or don't want to buy stuff is part of what makes engineering fun! And a pattern generator/programmable fuse doesn't exactly go together... for me it was just a convenience thing of not having to make another handheld box with very similar hardware.

I haven't really given much consideration to making them in any sort of quantities... I guess if I get a stable design and polish the software, I'd consider it. Right now, it's just a quick and dirty tool to get the job done.

That logic probe is great, it's more along the lines of what I'd hoped for when I bought my HP. The HP works, it's just that there is so much hassle switching everything between chip types.
Totally agreed... I've got an HP logic comparator as well, but that universal thing is annoying, and I can't see making an individual board for every chip... plus it's only limited to 16 pins (so no testing 245s and stuff). I really wanted to make an FPGA implementation of the logic comparator (so I could compare chips with states/memory)... but that'd take more effort than I want to put in right now.

DogP
 
First of all, I've had a portable 32 channel USB logic analyzer (Bugblat X34 - http://www.bugblat.com/products/x34.html ) for a while, which claimed to have a programming API, but no real documentation on using it. So I finally decided to sit down and figure it out.

Once I figured out how to use it, I decided to make a 32 channel logic probe. This allows me to connect it to an IC clip, then see the activity of all pins on the chip at once. Much quicker and easier than probing each pin with a normal logic probe.
Out of curiousity, why not just use the logic analyzer software to look at the state of each pin simultaneously (since you have the chip clips now to connect the channels up quickly)? I'm guessing your program is simpler to load and check at a glance (as with a real logic probe), just wondering.

Hurrah for homebrew!

LeChuck
 
That fuse replacement, signal generator thing, once you add XY, are you going to build and sell 'm ? Very cool device, esp. because it even does all resolutions !

I've been toying with the idea to build a simple XY generator for some time. It's such a hassle to need to hook the monitors up to a game all the time (esp. SW cockpits ;)).
 
Out of curiousity, why not just use the logic analyzer software to look at the state of each pin simultaneously (since you have the chip clips now to connect the channels up quickly)? I'm guessing your program is simpler to load and check at a glance (as with a real logic probe), just wondering.

Hurrah for homebrew!

LeChuck
I did it my way for a couple reasons... one - I like being able to just glance at a chip drawing, rather than a bunch of signals (and this makes it convenient by automatically masking off the unused pins once I specify how many pins the chip is). Also, I can't view all 32 lines at once in the regular software on my laptop screen.

My method also catches transitions better for the purpose of a logic probe. In the normal logic analyzer mode, the device responds with a stream of data from each trigger point. The way I'm using it for the logic probe, I query the device with the status since the last query... and I query it about 60 times per second. If you look at the screenshot, you'll notice there's 0, 1, and *. 0 means it's 0 now, and has been 0 since the last query. 1 means 1 now and 1 last time. * means there has been a transistion between the last query and now. This is great, because it'll catch short infrequent activity (similar to the beep/blinking light on a logic probe). In regular analyzer mode, unless I was lucky, I may have thought that pin was stuck (since it just gives me high resolution snapshots of short periods of time).

On the other hand, for the TTL checking program, I use the normal logic analyzer mode and get the high speed snapshots.

That fuse replacement, signal generator thing, once you add XY, are you going to build and sell 'm ? Very cool device, esp. because it even does all resolutions !

I've been toying with the idea to build a simple XY generator for some time. It's such a hassle to need to hook the monitors up to a game all the time (esp. SW cockpits ;)).
It's a possibility that I'd sell them... but I'd definitely have to put some effort into polishing it a little more. I also haven't really paid much attention to how much it all costs... should be much cheaper than any commercial solutions, but I really don't know how much.

DogP
 
I'd love to have this tool, polished or not. I could always burn new versions as you add polish. :) Very nice!
 
Very cool stuff.

The programmable fuse is a great idea. I bought some curcuit breakers from Bob Roberts, but they are all the same value (I think 1 amp). I bought them when I had a G-05 that was constantly blowing fuses on startup.

The "full chip" logic probe is very cool, too!

Nice job.
 
Nice. I've been considering getting a USB logic analyzers. Was mostly looking at the ~$150 price range, but the one you linked has some impressive specs.

I can't say I'd likely use a programmable circuit breaker (a fixed 5A pretty much does does the trick for me), but it's cool nonetheless.

The microcontroller pattern generator is cool. I've got a couple of Arduino's laying around... but I doubt that's what you used (based on the size of your box... same as the Blue ESR meter). If anyone has code to generate a few standard res test patterns with an arduino... hook me up.
 
The microcontroller pattern generator is cool. I've got a couple of Arduino's laying around... but I doubt that's what you used (based on the size of your box... same as the Blue ESR meter). If anyone has code to generate a few standard res test patterns with an arduino... hook me up.


No doubt. The modified LP is cool (already posted on it, I want one :)) but a reasonably priced pattern generator would be a big hit.
 
Thanks for the compliments! I put some of them to the test today during the repair party. Luckily, nothing was blowing fuses, so that part stayed unused. :) I did use the pattern generator, which sorta helped, though it definitely needs some work still. The logic probe and TTL checker got quite a bit of use on an Asteroids PCB... I think it saved a lot of time, though I can't call it a success, since we haven't fixed the board yet. :(

I'd love to have this tool, polished or not. I could always burn new versions as you add polish. :) Very nice!
Yeah, true... I'd most likely add a USB interface to the board for programming and stuff, so the firmware would be upgradable.

Nice. I've been considering getting a USB logic analyzers. Was mostly looking at the ~$150 price range, but the one you linked has some impressive specs.

I can't say I'd likely use a programmable circuit breaker (a fixed 5A pretty much does does the trick for me), but it's cool nonetheless.

The microcontroller pattern generator is cool. I've got a couple of Arduino's laying around... but I doubt that's what you used (based on the size of your box... same as the Blue ESR meter). If anyone has code to generate a few standard res test patterns with an arduino... hook me up.
An Arduino may be able to generate CGA, though I've never tried. I'm personally using a Parallax Propeller (http://www.parallax.com/propeller - 8 core microcontroller), which has a bunch of libraries for generating video (I modified the VGA one to generate CGA and EGA as well). It can also generate TV signals. I just modified a standard proto board to fit in the blue Hammond box, though if I make a real PCB for this, I could definitely make it smaller (probably put it in the smaller blue Hammond box).

No doubt. The modified LP is cool (already posted on it, I want one :)) but a reasonably priced pattern generator would be a big hit.
I've seen quite a few USB logic analyzers out there... at the time I bought this, it was on sale, and the software seemed pretty comparable to what was out there. Unfortunately, they're not on sale anymore, and it seems that they haven't updated the software in several years. :( A few more protocol analyzers would be a nice addition, though not that they really matter for most arcade stuff. Now that I've figured out the API, I'll definitely be able to do a LOT more with it.

DogP
 
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