[Quinn Dunki] has brought yet another wayward import tool into her garage. This one, all covered in cosmoline and radiating formaldehyde fumes, is a horizontal bandsaw.
Now, many of us have all have some experience with this particular model of horizontal saw. It waits for us at our work’s machine shop, daring us to rely on it during crunch time. It lingers in the corner of our hackerspace’s metalworking area, permanently stuck in the vertical position; at least until someone finally removes that stripped screw. Either that or it’s been cannibalized for its motor, the castings moldering in a corner of the boneyard.
This article follows on the heels of [Quinn]’s other work, a treatise on the calibration of a drill press, and it outlines all the steps one has to take to bring one of these misunderstood tools into consistent and reliable operation. It starts with cultivating a healthy distrust of the factory’s assurances that this device is, “calibrated,” and needs, “no further attention.” It is not, and it does. Guides have to be percussively maintained out of the blade’s way. Screws have to be loosened and adjusted. It takes some effort to get the machine running right and compromises will have to be made.
In the end though, with a high quality blade on, the machine performs quite well. Producing clean and quality cuts in a variety of materials. A welcome addition to the shop.
Oh sure, the thought of owning a happy whirring drill press of your very own is exciting, but have you really thought about it? It’s a big responsibility to welcome any tool into the home, even seemingly simple ones like a drill press. Lubricants, spindle runout, chuck mounts, tramming, and more [Quinn Dunki], of no small fame, helps us understand what it needs for happy intergration into its new workshop.
[Quin] covers her own drill press adventure from the first moments it was borne into her garage from the back of a truck to its final installation. She chose one of the affordable models from Grizzly, a Washington based company that does minimal cursory quality control on import machinery before passing on the cost to the consumer.
The first step after inspection and unpacking was to remove all the mysterious lubricants and protectants from the mill and replace them with quality alternatives. After the press is set-up she covers some problems that may be experience and their workarounds. For example, the Morse taper on the chuck had a few rough spots resulting in an incomplete fit. The chuck would work itself loose during heavier drilling operations. She works through the discovery and repair of this defect.
Full of useful tips like tramming the drill press and recommended maintenance, this is one of the best guides on this workshop staple that we’ve read.
In case you haven’t been reading Hackaday for the last few weeks, we just had an amazing 10th anniversary party in Pasadena this weekend, full of workshops, talks, and a party that reportedly went until four in the morning. One of the amazing hackers we invited to give a talk was [Quinn Dunki], creator of Veronica, the modern 6502 computer stuffed inside an old radio.
We first saw Veronica a few years ago, but [Quinn] figures she’s been building her computer for about five years now. She’s a software developer by trade that decided one day to dip her toes into the murky seas of hardware development and build a computer from the ground up. She chose the 6502 as the brains of her contraption, laid out everything on single-sided boards etched in a kitchen, and connected everything with a backplane. Right now it has a USB keyboard, (technically a PS/2 keyboard with a USB plug), NES controllers, a VGA display, and a monitor and Pong in ROM. [Quinn]’s goal was to build a computer that could program itself, and after five years, she’s accomplished that goal.
[Quinn] admits her software background was responsible for a few of her admittedly bad design choices; the VGA is generated by an ATMega microcontroller, working under the theory that if she could clock the micro fast enough, she could do VGA. She now believes an FPGA would have been a better choice for video output, but now that the video circuit is done, she probably won’t revisit that problem.
There is one thing missing from Veronica, and something that [Quinn] will be working on in the future: mass storage. Right now every program Veronica can run is either stored in ROM or entered via the keyboard. A hard drive is the next problem to solve, either with an SD card, or a Compact Flash or IDE hard drive.
[Quinn Dunki]’s Veronica, a homebrew computer based on the 6502 CPU, is coming along quite nicely. She’s just finished the input board that gives Veronica inputs for a keyboard and two old Nintendo gamepads. [Quinn] is building this computer all by her lonesome, including etching all the PCBs. She’s gotten very, very good at etching her own boards, but this input board did inspire a few facepalming moments.
In an earlier post, [Quinn] went over her PCB etching capabilities. As demonstrated by the pic above, she’s able to print 16 mil traces with 5 mil separation. This is just about as good as you can get with homebrew PCBs, but it’s not without its problems.
[Quinn] is using a photographic process for her boards where two copies of a mask is printed on an acetate sheet, doubled up, and laid down on a pre-sensitized copper board. The requirement for two layers of toner was found by experience – with only one layer of toner blocking UV light, [Quinn] got some terrible pitting on her traces and ground planes.
Two photographic masks means the masks must be precisely aligned. This example shows what happens when the acetate sheets are ever so slightly misaligned. With a 5 mil gap between traces, [Quinn] needs to align the masks to within ±2.5 mils; difficult to do by eye, and very hard once you factor in flexing and clamping them down to the copper board.
Even when this process goes perfectly, [Quinn] is pushing the limits of a laser printer. When printing at 600 dpi, the pixels of the print are about 1.5 mils. While GIMP, printer drivers, and the printer itself have some fancy software to help with the interpolation, [Quinn] is still seeing ‘bumps’ on the edges of perfectly aligned parts. This is one of those things that really makes you step back and realize how amazing fabbing PCBs at home actually is.
With most of the hardware for Veronica out of the way, it’s just about time for [Quinn] to start programming her baby. We’re not expecting a full-blown operating system and compiler, but those NES gamepads are probably crying out for some use.
[Quinn Dunki]’s awesome 6502-based computer is coming right along, and she decided it’s time to add one of the most important features found in the 80s microcomputers she’s inspired by – gamepads.
There were two ways of implementing gamepads back in the 80s. The Apple II analog joysticks used a potentiometer for each joystick axis along with a 556 timer chip to convert the resistance of a pot into a digital value. Analog controls are awesome, but a lot of hardware is required. The other option is the Atari/Commodore joystick that uses buttons for each direction. Surprisingly, these joysticks are inordinately expensive on the vintage market but a similar hardware setup – NES gamepads – are common, dirt cheap, and extremely well documented.
[Quinn] wrote a few bits of 6502 assembly to read these Nintendo controllers with Veronica’s 6522 VIA with the help of an ATMega168, and then everything went to crap.
In testing her setup, she found that sometimes the data line from the controller would be out of sync with the clock line. For four months, [Quinn] struggled with this problem and came up with one of two possible problems: either her circuit was bad, or the 6522 chip in Veronica was bad. You can guess which option is correct, but you’ll probably be wrong.
The problem turned out to be the 6522. It turns out this chip has a bug when it’s used with an external clock. In 40 years of production this hasn’t been fixed, but luckily 6502 wizard [Garth Wilson] has a solution for this problem: just add a flip-flop and everything’s kosher. If only this bug were mentioned in the current datasheets…
Now Veronica has two NES controller inputs and the requisite circuitry to make everything work. Video evidence below.
Continue reading “Veronica Gets A Pair Of Gamepads And A Bugged Chip”
I’ve been a software developer for quite a while. When you spend long enough inside a particular world, it’s easy to wind up with an ever-narrowing perspective. You start seeing everything from a software point of view. As the saying goes, when your only tool is a hammer, you tend to treat every problem as NP-Complete. Or something. I forget how that goes.
Anyway, the point is, it’s always good to broaden one’s horizons, and solve as many different kinds of problems as possible. To that end, I started to get into hobby electronics recently. The journey has been very enlightening in a number of ways.
Continue reading “Guest Rant: From Bits To Atoms”
[Quinn Dunki] pulled together many months worth of work by interfacing her GPU with the CPU. This is one of the major points in her Veronica project which aims to build a computer from the ground up.
We’ve seen quite a number of posts from her regarding the AVR-powered GPU. So far the development of that component has been happening separately from the 6502 centered CPU. But putting them together is anything but trivial. The timing issues that were so important to consider when developing the GPU get even hairier when it comes writing to the VRAM from an external component. Her first thought was to share a portion of the external RAM between the CPU and GPU as a way to push rendering commands from one to the other. This proved troublesome both in timing and in the number of pins available on the AVR chip. She ended up using something of a virtual register on the AVR chip that can receive commands from the CPU asynchronously. Timing dictates that these commands be written only during vertical blanking so this virtual register also acts as a status register to let the CPU know when it can send the next command.
Her post is packed with the theory behind the design, timing tests on the oscilloscope, and a rather intimidating schematic. But the most important part is the video showing her success in the end.