Nerdy Texts of Analog and Embedded Systems Wizardry

More new media art binnis for Cory.
This is basically an installation specific version of that little SBC/datalogger thingy I made. This one hangs out on a silly putting practice stand and plays back controller keypresses on a PS1 when you whack the ball.

To do this, first (well, first you design a weird SBC for new media artists, but) you replace the controller’s MCU (in this case some proprietary TQFP guy) and figure out where his data lines are. I happened to already know that the PS1 basically talks SPI. Some low temp solder and a rework station was used to perform said brain surgery.

The datalines and switch lines are then brought out to my baby, where it handles communication with the PS1. You can then record the game into it, put it on your PC, and do whatever mess you need to with the data.

That golf tee had a set of optical photointerrupters inside it which were originally used to keep track of how hard you hit the ball and how badly you shanked it. I wired one of them to just give me a clean square wave when the ball moved appreciably, since that’s all we needed to know for our game. The code on the “TiVo” had to get changed to account for this, which was no biggie.

Eventually, these things had to get re-built cause Cory got worried that art students would have a few too many PBRs at the openings and eventually whiff and take out one of the external PCBs. I ended up ultimately shock mounting them inside the stand itself. That’s also why Cory is a good client, because he is almost certainly correct. There is a good chance that would have happened before leaving Narrat1ve labs :-)

At the end of January I drove back to the city of heavenly taquerias and got jiggy with installing new brains in Remoc, just the cutesy wootsiest Elder God you could ever hope to meet!

Our boy assumed this position for many hours. Quoth the security ladies at the front desk, “Your Monster is all Drunked over!”

Here’s what the sensors look like in vivo. The little wire goes to a sheet of copper tape which is adhered to the inside of one of Remoc’s surfaces where he’ll be sensing touch (for instance, his finger — you’ll never guess what happens if you pull it). These plates are all of different sizes and shapes, and of accordingly make for different signal strengths on the output. They are also pretty close to one another sometimes and it certainly seems from looking at the ADC readings like there are some irritiating interactions between some sensors. If I did this again, they would each have an enable line and be polled sequentially. But.

The little boards get stuck down somewhere convenient and close to the tape, and then the more-or-less DC sensor signal is shuttled back through a cable.

Finally, the guy who sculpted Remoc managed to set his entire body cavity on fire shortly after all the copper tape and wiring was installed. This adds a real “wild card” element to the sensor system which keeps it fun!

Anyhoo, after a long install, he was back up and gibbering, and there was much rejoicing!

[Ed note: since this time, word has again arisen from the West that the cultists are stirring. It is likely this is not the last time we will sojourn to the Comer, dear reader, or as I like to call it, “Baby Boo Miskatonic”]

So sometime at the beginning of 2010 the sick children of Chicago set up a fuss looking for their monster again. You could hear them all the way from Brooklyn. Again, my guilt was heavy. Again, I made some stuff.

An introduction of what Remoc does is in order I guess. He’s basically a bigass toy that senses when little kids touch him in different spots and plays various games with them. He laughs, he cries. He may or may not be better than Cats. He also goes to sleep at night, sings songs, and has a weird interactive thermometer. He farts a lot. When he behaves, he’s kind of fun.

His memory and play pattern live on an SBC designed by my buddy Todd Squires which we used at the old toy company and affectionately call the toybrain (version 4). The TB4 was fine.

There was no real way to salvage most of the rest of Remoc’s old brain. There was a crappy class AB audio amp I put in which got way too hot, his touchsensor circuits were noise prone and also temperature sensitive, and his LED supply tended to go out of regulation when too many lights in the thermometer stayed on, and he got confused easily about time-of-day stuff if you turned his supply off. His eyeballs were light bulbs which burnt out (that was a committee decision, but). None of this was good.

His new brain boards (above) dealt with all this stuff. 2010 saw Remoc get new MOSFETs to run all his lights, a new audio amp, and a proper RTC with a ginormous battery for backup. More importantly, he got a bunch of precision opamps and a multichannel ADC to handle input from the touchsensors.

The touchsensors were actually fun to make. They’re an AVR which generates a crystal derived square wave (laziness on my part, and tunability. The generator could have been a logic gate or any crystal clock circuit really, although the programmable chip provided fudge room which I didn’t [and hopefully won’t] need) and drives it through a resistor to whatever gnarly sensor plate you have, and then filters and rectifies what’s left. They use hand capacitance to form a variable RC filter; the output of this device is a voltage which is inversely proportional to the capacitance at the sensing node. Not perfect, but pretty good. These sensors also use 1/8″ cables to carry power, ground, and signal, cause 1/8″ cables are cheap and promised to make wiring the beast a lot easier.

The thermometer. Some SMT LEDs on a stick. Yaaaawn.

All this stuff got packed up to schelp to Chicago.

So over the last couple years I’ve been building different variations on this thing for my client/buddy Cory. It’s had many names but the one we tended to call it the most often was the “Video Game TiVo”. It’s basically an AVR with a ton of Atmel Dataflash as well as some Vregs, level translators, and RS-232 chips.

The idea with these guys is that they sit around on a video game controller and log what the user is doing, and then spit that biz back out when you tell them to. The original ones simply hung out watching or asserting the actual switch lines using WPUs and the like, and as time went by they began to actually replace the controller interface entirely and deal exclusively with serial. Depending on the game system, they can sometimes play a game back deterministically, but mostly not because of RNG and/or timing issues. Either way, they’ll record MONTHS of game and can loop arbitrarily, etc etc. They also have a fancy terminal built in for communicating with a PC and recognizing different video game consoles.

Cory wanted them so he could throw infinite gutterballs in Playstation Bowling games. They do that just fine :-)

This one was tested on a PS1 and the canonical bowling.
This January I had geared up to finally make a TON of them so Cory could just have them handy and not need to call me when he needed one, and this was the final test run before we went into production.

This labor of love and money was also for Cory. Basically, there are these two weird Chinese merchandise stands that get sold at places like Spencer’s, and Cory was like, make one go a few percent slower than the other one. I think originally he was thinking stepper motors or something which is why I got involved, but it was a lot more low-level (in a wedge-screw-pulley-inclined-plane kind of way and not so much an assembly language kind of way) than that.

Inside one of these things is a reversible synchronous AC motor with a toothed belt linkage. A quick test with the Variac proved that, yes, their speed was independent of input voltage. Turned out the easiest way to get the speed differential was to pull the original transmission parts and replace them with XL drive pulleys and belts. The OG stands use a 3mm (I think) Chinese pitch system which is kinda hard to find around these parts. McMaster saved the day as usual but now I get my goodies from my pulley people at B&B Manufacturing who have likely forgotten more about power transmission than I ever hope to know. One thing about McMaster, they aren’t shy about leaving other peoples’ labels on their parts :-)

Doing this meant a lot of cutting and tapping, which is fun for me because I rarely get to do it professionally. To wit:

I had to drill out the pulleys (they’re made for 0.250″ shafts and the shafts in the stands are 7mm) and got all noided about leaving tap magic on them because I was worried about the belts not liking it. This was part of the washing/drying process and won me zero points with my housemates.