Suitcase Computer Reborn With Raspberry Pi Inside

May 17, 2018 by 48 Comments

Fun fact, the Osborne 1 debuted with a price tag equivalent to about $5,000 in today’s value. With a gigantic 9″ screen and twin floppy drives (for making mix tapes, right?) the real miracle of the machine was its portability, something unheard of at the time. The retrocomputing trend is to lovingly and carefully restore these old machines to their former glory, regardless of how clunky or underpowered they are by modern standards. But sometimes they can’t be saved yet it’s still possible to gut and rebuild the machine with modern hardware, like with this Raspberry Pi used to revive an Osborne 1.

Purists will turn their nose up at this one, and we admit that this one feels a little like “restoring” radios from the 30s by chucking out the original chassis and throwing in a streaming player. But [koff1979] went to a lot of effort to keep the original Osborne look and feel in the final product. We imagine that with the original guts replaced by a Pi and a small LCD display taking the place of the 80 character by 24 line CRT, the machine is less strain on the shoulder when carrying it around. (We hear the original Osborne 1 was portable in the same way that an anvil is technically portable.) The Pi runs an emulator to get the original CP/M experience; it even runs Wordstar. The tricky part about this build was making the original keyboard talk to the Pi, which was accomplished with an Arduino that translates key presses to USB.

As an aside, if reading this has given you a twinge of nostalgia and you’re on the Eastern seaboard you may want to check out more vintage gear at the VCF East this weekend. If you hail from Europe, get your hack on with CP/M and a retrocomputing badge at Hackaday Belgrade one wee from now.

We’ve seen the Raspberry Pi pressed into retrocomputing duty before, of course. Here’s one used to emulate a Commodore 1541 disk drive, and another in the laptop Clive Sinclair never built.

Continue reading “Suitcase Computer Reborn With Raspberry Pi Inside” →

No-Battery HD Video Streaming Does It With Backscatter

May 17, 2018 by 49 Comments

What if Google Glass didn’t have a battery? That’s not too far fetched. This battery-free HD video streaming camera could be built into a pair of eyeglass frames to stream HD video to a nearby phone or other receiver using no bulky batteries or external power source. Researchers at the University of Washington are using backscatter to pull this off.

The problem is that a camera which streams HD video wirelessly to a receiver consumes over 1 watt due to the need for a digital processor and transmitter. The researchers have separated the processing hardware into the receiving unit. They then send the analog pixels from the camera sensor directly to backscatter hardware. Backscatter involves reflecting received waves back to where they came from. By adding the video signal to those reflected waves, they eliminated the need for the power-hungry transmitter. The full details are in their paper (PDF), but here are the highlights.

Battery-free camera design approach

On the camera side, the pixel voltages (CAM Out) are an analog signal which is fed into a comparator along with a triangular waveform. Wherever the triangle wave’s voltage is lower than the pixel voltage, the comparator outputs a 0, otherwise, it outputs a 1. In this way, the pixel voltage is converted to different pulse widths. The triangular waveform’s minimum and maximum voltages are selected such that they cover the full possible range of the camera voltages.

The sub-carrier modulation with the XOR gate in the diagram is there to address the problem of self-interference. This is unwanted interference from the transmitter of the same frequency as the carrier. And so the PWM output is converted to a different frequency using a sub-carrier. The receiver can then filter out the interference. The XOR gate is actually part of an FPGA which also inserts frame and line synchronization patterns.

They tested two different implementations with this circuit design, a 112 x 112 grayscale one at up to 13 frames per second (fps) and an HD one. Unfortunately, no HD camera on the market gives access to the raw analog pixel outputs so they took HD video from a laptop using USB and ran that through a DAC and then into their PWM converter. The USB limited it to 10 fps.

The result is that video streaming at 720p and 10 fps uses as low as 250 μW and can be backscattered up to sixteen feet. They also simulated an ASIC which achieved 720p and 1080p at 60 fps using 321 μW and 806 μW respectively. See the video below for an animated explanation and a demonstration. The resulting video is quite impressive for passive power only.

If the University of Washington seems familiar in the context of backscatter, that’s because we’ve previously covered their battery-free (almost) cell phone. Though they’re not the only ones experimenting with it. Here’s where backscatter is being used for a soil network. All of this involves power harvesting, and now’s a great time to start brushing up on these concepts and building your own prototypes. The Hackaday Prize includes a Power Harvesting Challenge this year.

Continue reading “No-Battery HD Video Streaming Does It With Backscatter” →

The Solid State Weather Station

May 17, 2018 by 60 Comments

Building personal weather stations has become easier now than ever before, thanks to all the improvements in sensors, electronics, and prototyping techniques. The availability of cheap networking modules allows us to make sure these IoT devices can transmit their information to public databases, thereby providing local communities with relevant weather data about their immediate surroundings.

[Manolis Nikiforakis] is attempting to build the Weather Pyramid — a completely solid-state, maintenance free, energy and communications autonomous weather sensing device, designed for mass scale deployment. Typically, a weather station has sensors for measuring temperature, pressure, humidity, wind speed and rainfall. While most of these parameters can be measured using solid-state sensors, getting wind speed, wind direction and rainfall numbers usually require some form of electro-mechanical devices.

The construction of such sensors is tricky and non-trivial. When planning to deploy in large numbers, you also need to ensure they are low-cost, easy to install and don’t require frequent maintenance. Eliminating all of these problems could result in more reliable, low-cost weather stations to be built, which can then be installed in large numbers at remote locations.

[Manolis] has some ideas on how he can solve these problems. For wind speed and direction, he plans to obtain readings from the accelerometer, gyroscope, and compass in an inertial sensor (IMU), possibly the MPU-9150. The plan is to track the motion of the IMU sensor as it swings freely from a tether like a pendulum. He has done some paper-napkin calculations and he seems confident that it will provide the desired results when he tests his prototype. Rainfall measurement will be done via capacitive sensing, using either a dedicated sensor such as the MPR121 or the built-in touch capability in the ESP32. The design and arrangement of the electrode tracks will be important to measure the rainfall correctly by sensing the drops. The size, shape and weight distribution of the enclosure where the sensors will be installed is going to be critical too since it will impact the range, resolution, and accuracy of the instrument. [Manolis] is working on several design ideas that he intends to try out before deciding if the whole weather station will be inside the swinging enclosure, or just the sensors.

If you have any feedback to offer before he proceeds further, let him know via the comments below.

The HackadayPrize2018 is Sponsored by:

Circuit VR: Current Mirrors

May 17, 2018 by 18 Comments

Last time we looked at Spice models of a current sink. We didn’t look at some of the problems involved with a simple sink, and for many practical applications, they are perfectly adequate. However, you’ll often see more devices used to improve the characteristics of the current sink or source. In particular, a common design is a current mirror which copies a current from one device to another. Usually, the device that sets the current is in a configuration that makes it very stable while the other device handles the load current.

For example, some transistor parameters vary based on the output voltage which causes small nonlinearities in the output. But if the setting transistor has a fixed voltage across it, that won’t be a problem. The only problem with mirror schemes is that the transistors involved all have to match in key characteristics. For that reason, mirrors are usually better on ICs where the transistors are all more or less the same. You can get discrete transistors that have multiple devices built on a single substrate, but these are not very common.

Continue reading “Circuit VR: Current Mirrors” →

The Pros And Cons Of Microcontrollers For Boost Converters

May 17, 2018 by 37 Comments

It never fails — we post a somewhat simple project using a microcontroller and someone points out that it could have been accomplished better with a 555 timer or discrete transistors or even a couple of vacuum tubes. We welcome the critiques, of course; after all, thoughtful feedback is the point of the comment section. Sometimes the anti-Arduino crowd has a point, but as [Great Scott!] demonstrates with this microcontroller-less boost converter, other times it just makes sense to code your way out of a problem.

Built mainly as a comeback to naysayers on his original boost-converter circuit, which relied on an ATtiny85, [Great Scott!] had to go to considerable lengths to recreate what he did with ease using a microcontroller. He started with a quick demo using a MOSFET driver and a PWM signal from a function generator, which does the job of boosting the voltage, but lacks the feedback needed to control for varying loads.

Ironically relying on a block diagram for a commercial boost controller chip, which is probably the “right” tool for the job he put together the final circuit from a largish handful of components. Two op amps form the oscillator, another is used as a differential amp to monitor the output voltage, and the last one is a used as a comparator to create the PWM signal to control the MOSFET. It works, to be sure, but at the cost of a lot of effort, expense, and perf board real estate. What’s worse, there’s no simple path to adding functionality, like there would be for a microcontroller-based design.

Of course there are circuits where microcontrollers make no sense, but [Great Scott!] makes a good case for boost converters not being one of them if you insist on DIYing. If you’re behind on the basics of DC-DC converters, fear not — we’ve covered that before.

Continue reading “The Pros And Cons Of Microcontrollers For Boost Converters” →

Review: FG-100 DDS Function Generator

May 17, 2018 by 44 Comments

I don’t have a signal generator, or more specifically I don’t have a low frequency signal generator or a function generator. Recently this fact collided with my innocent pleasure in buying cheap stuff of sometimes questionable quality. A quick search of your favourite e-commerce site and vendor of voice-controlled internet appliances turned up an FG-100 low frequency 1Hz to 500kHz DDS function generator for only £15 ($21), what was not to like? I was sold, so placed my order and eagerly awaited the instrument’s arrival.

The missing function generator is a gap in the array of electronic test instruments on my bench, and it’s one that maybe isn’t as common a device as it once might have been. My RF needs are served by a venerable Advance signal generator from the 1960s, a lucky find years ago in the back room of Stewart of Reading, but at the bottom end of the spectrum my capabilities are meagre. So why do I need another bench tool?

It’s worth explaining what these devices are, and what their capabilities should be. In simple terms they create a variety of waveforms at a frequency and amplitude defined by their user. In general something described as a signal generator will only produce one waveform such as a sine or a square wave, while a function generator will produce a variety such as sine, square, and sawtooth waves. More accomplished function generators will also allow the production of arbitrary waveforms defined by the user. It is important that these instruments have some level of calibration both in terms of their frequency and the amplitude of their output. It is normal for the output to range from a small fraction of a volt to several volts. How would the FG-100 meet these requirements? Onward to my review of this curiously inexpensive offering.

Continue reading “Review: FG-100 DDS Function Generator” →

Open Gaming To Everyone With A Controller Meant To Be Hacked

May 17, 2018 by 35 Comments

Gaming controllers have come a long way from an Atari 2600’s single button and digital joystick. As games grew more sophisticated, so did the controllers. This development had a dark side – controllers’ growing complexity have made it increasingly difficult for different-abled bodies to join in the fun. Microsoft has extended an invitation to this audience with their upcoming Xbox Adaptive Controller.

Creative minds have been working on this problem for a while, building an ecosystem of controller hacks to get more people into gaming. These projects require solving problems in two broad categories: the first is to interface with input devices that match a specific user’s needs, the second is then integration into target game device’s control infrastructure.

The value of XAC is eliminating the second category of work and making it reliable: it takes care of all the housekeeping overhead of creating a custom Xbox controller, from power management to wireless communication. As for input device interface, every control needed to play on a Xbox is individually mapped to a standard 3.5 mm jack. Some are pure digital ports, others can transfer an analog value. A 3.5mm plug is a proven consumer-friendly interface that’s easy to work on by anyone who wants to pick up a soldering iron, making this array of jacks a wide-open gateway to limitless possibilities. The 3.5 mm jacks make it easy to build specific configurations, and make it easy for less-technical people to reconfigure for a different player or different game.

We love to see our hacker creativeness applied to help people live normal lives. Making it easy to hack up a custom gaming controller may not be earth shattering, but don’t underestimate the importance of letting people feel included. It does transform lives, one at a time. Plus, it looks like fun to play with.

Continue reading “Open Gaming To Everyone With A Controller Meant To Be Hacked” →