Squeezing A Minimalist 6502 Retrocomputer Onto A Single Breadboard

January 4, 2023 by 11 Comments

Over the years, and especially lately, we’ve seen tons of single-board retrocomputer builds. That’s fine with us — the more, the merrier. But they all start to run together a bit, with little to distinguish between them. Not so this about-as-compact-as-possible 6502 computer that fits on a single breadboard.

Now, when you do the math, it seems like there’s no way that [Anders Nielsen] would have been able to fit even a minimal chipset onto a standard solderless breadboard. The 40-pin 6502 alone takes up nearly two-thirds of the connections available; add in equally large but necessary chips like the 6522 interface adapter, ROM and RAM chips, and some support ICs, and one breadboard isn’t going to cut it. Luckily, some frugal engineers at MOS back in the 70s came up with the 6507, a variant on the 6502 in a 28-pin DIP. The other key to this build is the 6532 RAM-I/O-timer chip or RIOT, which puts a tiny amount of RAM and some IO lines on a single 40-pin DIP. Along with a 28-pin ROM, a 14-pin hex inverter, and a little crystal oscillator, the entire chipset just barely fits on a single breadboard.

But what can this minimalist 6502 actually do? As you can see in the video below, anything a 555 timer can do, and maybe a little bit more. That’s not a dig, of course — [Anders] actually calls out his initial blinkenlight application as a little more than a glorified 555, and actually comes up with a marginally more complex application just to prove the point. The interesting part here is dealing with the constraints imposed by the limited resources available on this machine.

We’re looking forward to whatever comes next for this clever build. It’s hard to see how some of the plans [Anders] has for it will still fit on a single breadboard, though — these things tend to spread out as they go.

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Bypass Defective STDP9320 Video Controller On Wacom Cintiq Companion 2

January 4, 2023 by 8 Comments

Some products seem to have a part of two that’s pretty much guaranteed to end up dying on you. In the case of the 2015-vintage Wacom Cintiq Companion 2, this turns out to be the so-called Athena chip, which switches the display input between the HDMI port and internal display controller. This allows for use in both standalone mode (tablet), as well as companion mode, where it acts as a drawing tablet for a connected PC. When confronted with such a faulty device, [neutrino] found and applied a simple fix: bypassing the Athena chip altogether.

This fix is recommended by the Repair Preservation Group’s wiki page on the topic, noting that this will permanently disable its use as an external display without additional repairs to recreate the functionality of the removed chip. This STDP9320 (PDF) part by ST Microelectronics is described as a ‘Premium high resolution multimedia monitor controller with 3D video’ and contains a wide range of video scalers, a HDMI receiver, DisplayPort (including embedded DP) support. With this fix, the Cintiq Companion 2’s Intel CPU’s graphics core is directly connected to the display’s eDP input, along with a range of voltages and enable pins.

What the exact reason is for the STDP9320 dying after a few years with what appears to be some kind of internal power failure or short, but this bypass fix at least restores standalone functionality. Sourcing a replacement for this obsolete IC seems possible, but a big gamble. Sadly, it would seem that this Wacom device will no longer be a companion for much longer.

Near Field EMI Probes: Any Good?

January 3, 2023 by 17 Comments

[Learnelectronics] purchased some near-field EMI probes for his tiny spectrum analyzer for about $5 on sale. Could they be any good at that price? Watch the video below and find out.

The probes arrived as a kit with four probes: three circular ones for sensing the H field and a stubby probe for sensing E fields (although the video gets this backward, by the way). There’s not much to them, but for the price, it probably isn’t worth making them yourself if your concern is the cost. Now, if you just want to make your own, we get that, too, but don’t expect to save much money.

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Continuous Printing On LCD Resin Printer: No More Wasted Time On Peeling? Is It Possible?

January 3, 2023 by 20 Comments

Anyone who has done any amount of 3D printing with SLA printers is probably well aware of the peeling step with each layer. This involves the newly printed layer being pulled away from the FEP film that is attached to the bottom of the resin vat. Due to the forces involved, the retraction speed of the build plate on the Z-axis has to be carefully tuned to not have something terrible happen, like the object being pulled off the build plate. Ultimately this is what limits SLA print speed, yet [Jan Mrázek] postulates that replacing the FEP with an oxygen-rich layer can help here.

The principle is relatively simple: the presence of oxygen inhibits the curing of resin, which is why for fast curing of resin parts you want to do so in a low oxygen environment, such as when submerged in water. Commercial printers by Carbon use a patented method called “continuous liquid interface production” (CLIP), with resin printers by other companies using a variety of other (also patented) methods that reduce or remove the need for peeling. Theoretically by using an oxygen-permeating layer instead of the FEP film, even a consumer grade SLA printer can skip the peeling step.

The initial attempt by [Jan] to create an oxygen-permeating silicone film to replace the FEP film worked great for about 10 layers, until it seems the oxygen available to the resin ran out and the peeling force became too much. Next attempts involved trying to create an oxygen replenishment mechanism, but unfortunately without much success so far.

Regardless of these setbacks, it’s an interesting research direction that could make cheap consumer-level SLA printers that much more efficient.

(Thumbnail image: the silicone sheet prior to attaching. Heading image: the silicone sheet attached to a resin vat. Both images by [Jan Mrázek])

HP 33120A Repair: Shutting Down The Eye Of Sauron

January 3, 2023 by 22 Comments

When a friend of [Tom Verbeure] came into possession of two HP 33120A 15 MHz function/arbitrary waveform generators, he could not resist giving them a try. Although not exactly high-end units, the HP 33120A makes for a pretty nice unit for a home lab. During the first test run, however, [Tom] discovered that one of the units had a dead output, which made it rather useless. Undeterred, [Tom] set to work diagnosing it, helped by the repair manual and full schematics.

While the cause was quickly tracked down to the general area around an exploded MLCC, fixing the fried Zener diode that may have initiated the short on the -15V rail revealed an unpleasant surprise. To [Tom]’s horror, he saw a portal to Hell itself open when part of the PCB caught on fire due to an internal short. After making sure to capture a video of this event, he then proceeded to use a thermal camera to track down the hot spot and uses a drill to remove the short.

While one can argue with the use of a drill to remove shorts on inner layers of a PCB, ultimately the fix was effective. A look on the schematic and comparison with the functioning 33120A unit later, all it took was two bodge wires to restore functionality. After this event, [Tom]’s friend gave him the repaired unit as thanks, and definitely not because [Tom] had begun to refer to it as ‘his precious’.

The Crawlspace Crawler

January 3, 2023 by 35 Comments

This crawlspace crawler FPV robot is a fairly simple build. [Jeff G] bought a boxy chassis kit with frame, motors, and wheels, mounted lights and camera, and we get to see it in action (video, embedded below).

As always, the details are where it’s at, and his overview covers most of the high points. [Jeff] went for relatively slow 60 RPM motors so that he’d have plenty of grunt. The FPV setup is particularly simple – he bought a cheap Flysky i6 transmitter and receiver, and an Eachine TX05 all-in-one camera and transmitter. An interesting choice was a USB UVC video receiver so he can watch the footage on a computer, tablet, or a cell phone, which means he didn’t have to shell out for expensive FPV goggles. We also love the sticks-and-zip-ties used as feelers, letting him know when he’s about to get stuck, but that also serve as a visual frame for the camera.

The FPV Contest just came to an end, and we’ll be announcing the winners soon! If you find any inspiration there for your own project, [Jeff]’s simple basis here should get you started on the right track.

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Fool A Drone With A Fixed Battery

January 3, 2023 by 21 Comments

Lithium-ion and lithium-polymer rechargeable batteries have given us previously impossible heights of electronics power and miniaturization, but there’s a downside they have brought along with them. When a battery pack has to contain electronics for balancing cells, it’s very easy for a manufacturer to include extra functions such as locking down the battery. Repair a battery, replace cells, or use a third-party battery, and it won’t work. [Zolly] has this with a DJI Mavic Mini pack, and shares with us a method for bypassing it.

The pack talks to the multi-rotor with a serial line, and the hack involves interrupting that line at the opportune moment to stop it telling its host that things are amiss. Which is a good start — but we can’t help hacing some misgivings around the rest of the work. Disconnecting the balance line between the two cells and fooling the Battery Management System (BMS) with a resistive divider seems to us like a recipe of disaster, as does bypassing the protection MOSFETs with a piece of wire. It may work, and in theory the cells can be charged safely with an external balance charger, but we’re not sure we’d like to have a pack thus modified lying around the shop.

It does serve as a reminder that BMS boards can sometimes infuriatingly lock their owners out. We once encountered this with a second-generation iBook battery that came back to life after a BMS reset, but it’s still not something to go into unwarily. Read our guide to battery packs and BMS boards to know more.

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