Zero Ordered ++

A project log for sdramThingZero - 133MS/s 32-bit Logic Analyzer

Add an old SDRAM DIMM to your SBC for a 133MS/s 32-bit Logic Analyzer, add ADCs for a Scope...

Eric HertzEric Hertz 10/01/2016 at 13:246 Comments

UPDATE 10-9-16: OMG There's a composite output! Whew, none of that ridonculous HDMI hacking necessary in the near future. And where the heck did my SD-card reader/writer go...?


Alright! I've placed an order for My Very First Single-Board-Computer, only $9.42 total, with the cheapest shipping option and "shipping may be delayed due to quantities" as well as "limit: 1" while the "quantity available" *counter* says "in stock" so... yahknow... whatever.

Also placed an order a couple weeks ago that just came for some microSD cards, 4GB should be enough, right...? And, fergodsakes, it's about time I have a Nibbler Tool, again... I used my old one to death (quite literally its death, beyond my hacking-abilities to keep usable) over several years, and have been kicking myself for not having another, for years now. $10.

Also just received an order with some 74AC574's as well as some 74AC multiplexers, and a few other things... Three orders total, so far, <$100, including a few toys, as well. (seriously: check out this alphanumeric display: it's WEIRD! How could any respectable blinky-lover resist that? It's got weird-shaped *dots* in two corners! Some vague ideas of something along the lines of "Snake" or the "Game Of Life"...)

Oh, and I couldn't resist a couple 40107's, seeing as how that's my user-number...

One realization re: PiZero: Yeahp, I don't have a screen with DVI/HDMI input... I think I can hack something together, but it'll definitely be a hack. At one point a couple years back I did a DVI -> FPD-Link converter, it should probably work, but then I need some adapters from Micro-HDMI->DVI, or something... And the micro->HDMI converters were cheap at that place, but not in stock (figures). We'll see where this goes. Oh, and I finally managed to dig out the fluorescent-tube used in #my very first binary-clock (and many other projects, prior)... turns out the ground-wire got ripped from the tube, but luckily the tube is in-tact as well as the solder-point. FHWEW! So, DVI->FPD-Link may be "the path." Alternatively, I have another LCD display to which I once attached an old Plasma's TV-Tuner board... (which also happens to have HDMI inputs). #Ridiculous [LCD] Display Hacks It's a bit hokey (some of the color-bits are misaligned), but pseudo-functional, and maybe worth fixing-right. Oh, and I might be acquiring a "new" PowerBook G4, from a generous (and extremely patient) donor, to replace the old one, whose motherboard died... which means I'll be needing the Single-Pixel-to-Dual-Pixel converter I'd repurposed for the Plasma->LCD converter, to install that 1400x1050 display back in the new PBG4 (1024x768 is painful!)... So, maybe I'll be needing another of those converters. Those chips ain't cheap. Oy. Oh yeah, and I'd need to redesign it slightly to remap those color-bits... if I wanted to do it right for the Plasma->LCD converter. Weee!

no... dagnabbit... if I'm already building a new circuit, rather'n just soldering up a prebuilt PCB... then the logical-conclusion would be to work it for the *other* LCD display, which just happens to have speakers. So, I'd need... Well, that display is dual-pixel, as well, but dual-pixel *parallel*... the TV-tuner board is single-pixel LVDS-output, with, again, a weird color-bit-mapping. So... I gotsta get an LVDS->Parallel converter (which, actually, I think I have a few, just not the ones the *other* board was designed for, savings: $8). But, then, I need to convert the single-pixel parallel-data into dual-pixel *parallel* data... which would need... a couple 8-bit D-Q latches... No, wait... a couple *for each color* (so six) (and I just happened to invest in a bunch of 574's), and... Hmm, something to divide the pixel-clock in half... another D-Q latch should do... Maybe an inverter or some other glue-logic... I might actually already own all the parts I need, only major problem is the tiny pin-spacing of the LVDS-receivers... Don't *really* feel like designing a PCB for this one-off ridonculosity. (we'll call it "art"). Oh, maybe I can get away with only 3 8-bit DQ latches... Why didn't I invest in some 50+pin TSSOP breakouts...? Ah, but there's a TQFP-100 breakout I could cut in half, and only have a few pins hanging on each side to be dead-bugged... Only thing is, how do I assure that it always picks up the *first* pixel on the latch...? (how many pixel-clocks does the receiver take to sync its PLL?). Guess I could throw in a button to inject a pixel-clock (or a few dozen, with bouncing and all) if it's not synced properly...

So, if I've got this straight, I should be able to take an old 15in VGA-input LCD monitor with built-in speakers, and cludge-together a converter to connect an old (dead) plasma-TV's TV-Tuner board... 15in 1024x768 with two HDMI inputs, TV-tuner, VGA (via RCA-jacks!), a couple composite inputs, and a few other doodads. And... then I'll have something I can connect to the $5 PiZero.

So, how do I determine the color-bit mapping...? I *know* it's non-standard, as I spent quite a bit of effort fiddling with the brightness-settings (really low) to get it working with a standard FPD-Link display... So those high-bits are mis-located, is the logical conclusion. I suppose I could drive it with an HDMI source, 'scope the outputs of the LVDS->Parallel chip when driving it with, say, specific RGB-values (plausibly via GIMP?)... But, then, do I need to worry about whether there's color-correction going on via the OS...? Oh, and... I don't actually have a video-card with DVI/HDMI... Though, the "new" PBG4 does... so, hmmm.... But, then, the TV-Tuner has its own color-"correction" via brightness/contrast, as well as temperature, and more... so, realistically, quite unlikely I'll find a 1:1 mapping from in to out...

mwahahahahahaha... D'yah see why that project-page is called #Ridiculous [LCD] Display Hacks...?


So, again, a Tremendous Thank You to HaD, its judges, and many other folk, for awarding this project some moolah! First things first, had to pay off a dangerously-high utility-bill, which sucked up the majority of the winnings. Wasn't sure how I was gonna catch up on that, and this was impeccable timing. So again, Much Thanks To You! After that, there's a little bit left for project-stuff...


Still have a Digikey order in the works... need some high-speed 74x00's (NANDs) and some other things that weren't available at the other suppliers. But, was still planning on going the route of DIP-packaged parts for now... PCB-stuff is definitely in the plans, but I figure there's still some prototyping to be done. (e.g., see the last log).

Interestingly, @Ted Yapo commented in a previous log about the 74AC series, and it would seem that series is *still* amongst the fastest-available in DIP form. So, I'll probably still be fighting the AC's quirks (ground-bounce, etc., again mentioned in that log, and a good link in there somewhere, as well), despite the series' being produced well over two decades ago. (Thanks, Ted, for giving me the heads-up on that stuff!).

Don't be mistaken, faster and maybe-less-ground-bounce-prone series seem to exist in TSSOP-form... Oh, and I ordered a bunch of TSSOP-breakout-boards at something like $0.60-apiece... I ordered 10, but maybe shoulda sprung for more and avoided the AC-series altogether... hmm... Well, that order's here, so nothing to be done now... Still, maybe I should rethink that Digikey order and maybe even develop my own TSSOP breakouts and order PCBs from the cheapo-fabs...?


DIMM sockets... EXPENSIVE at the regular sources... ($17 apiece at one place!) if not obsolete and no longer carried... That means ebay or maybe ali-express...? These options are the sort I like to avoid... What're the odds the DIMM sockets I order for uber-cheap and with darn-near no documentation nor reputable part-numbers will actually have the notches in the right places? Maybe they're so cheap because no one wants sockets for Registered DIMMs, yahknow...? And will those supplie[r]s still be around should I decide to place another order later down the road...? Will others match the pad-layout? So strange, considering how common they once were, in darn-near every desktop computer for nearly a decade. Maybe I should just run down to the PC-recycling place and buy up all their old PC66-133 MoBos and whip out the heat-gun.

Or, maybe better-yet, keep this project as not a *product* but write up decent instructions for the DIYers willing to scrap/crop their own motherboards...

(Those edges would've turned out *much straighter* with my new nibbler tool, rather'n tin-snips!)


Nah... If we're trying to bump this up to 133MHz (and beyond...? Didja realize there was a PC166?!) hand-routing like that, especially with the traces already onboard, and the need to jump *off-board* is probably not conducive...

Anyways, PiZero allegedly shipped, should probably be here *long* before I'm ready to power it up... and yahknow, long long before I have the bus-system running to connect sTZero. OTOH, I do have all those '574's now... hmm...


Ted Yapo wrote 10/05/2016 at 12:33 point

You will have to post a picture of the Zero when it arrives.  I still doubt that they exist :-)  I've built Pi's into two projects, and have another one doing some DNS things on my home network, but I've never actually connected one to a monitor - only used ssh.  Sometimes, I forget they even have the port...

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Eric Hertz wrote 10/05/2016 at 12:53 point

Interesting point... Does the Zero (allegedly) have ethernet? erm... doesn't look like it. 

So, then serial-port... 

Console-based logic-analysis? I'm OK with that, not too familiar with GUI-programming, anyhow... then again, not familiar at all with ncurses. And webserver doesn't make sense without ethernet/wifi... OTOH, Sigrok is already well-developed, why reinvent the wheel?

Erm, crud, I forgot that its USB ports are weird, too... would need an adapter (and hub) to hook up a KB/Mouse... Now we're nearing the cost and size of a regular-pi. Bah!

I suppose I could drop the Zero altogether, and just wire sTZ to an FT2232H and use it with my regular-ol' computer which already has monitors and a keyboard and a mouse ;)

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Ted Yapo wrote 10/05/2016 at 13:14 point

I would be slightly disappointed if at least one version of your analyzer didn't output ASCII waveforms in the style of your schematics :-)

But that's probably impractical in the long run. Using a display with the Pi may be your best bet.

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Craig Hissett wrote 10/05/2016 at 15:14 point

The Pi Zero (and also the A+) can be configured to use Linux Gadget modes, such as the serial/ethernet gadget. This way you can SSH into your Zero via USB, and only need the one USB cable to access it:

Definitely worth having a look at!

It can also be done with the A+ model too.

Hope this helps :)

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Eric Hertz wrote 10/05/2016 at 23:39 point

@Craig Hissett

Of course! Why didn't I see it before?!

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Eric Hertz wrote 10/05/2016 at 14:19 point

Haha, I was contemplating when I wrote that what those timing-diagrams would look like in ASCII, what with zooming and scrolling through literally millions of samples. Maybe they'd be drawn vertically instead of horizontally ;)

I have an old KayPro logic analyzer... Been meaning to boot that thing up and see what its timing-diagrams look like. (nevermind figure out how to copy its diskette before it's too late).

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