Students Set Sights on DIY Eye Exams

What if you could give yourself a standard eye exam at home? That’s the idea behind [Joel, Margot, and Yuchen]’s final project for [Bruce Land]’s ECE 4760—simulating the standard Snellen eye chart that tests visual acuity from an actual or simulated distance of 20 feet.

This test is a bit different, though. Letters are presented one by one on a TFT display, and the user must identify each letter by speaking into a microphone. As long as the user guesses correctly, the system shows smaller and smaller letters until the size equivalent to the 20/20 line of the Snellen chart is reached.

Since the project relies on speech recognition, the group had to consider things like background noise and the differences in human voices. They use a bandpass filter to screen out frequencies that fall outside the human vocal range. In order to determine the letter spoken, the PIC32 collects the first 256 and last 256 samples, stores them in two arrays, and performs FFT on the first set. The second set of samples undergoe Mel transformation, which helps the PIC assess the sample logarithmically. Finally, the system determines whether it should show a new letter at the same size, a new letter at a smaller size, or end the exam.

While this is not meant to replace eye exams done by certified professionals, it is an interesting project that is true to the principles of the Snellen eye chart. The only thing that might make this better is an e-ink display to make the letters crisp. We’d like to see Snellen’s tumbling E chart implemented as well for children who don’t yet know the alphabet, although that would probably require a vastly different input method. Be sure to check out the demonstration video after the break.

Don’t know who [Bruce Land] is? Of course he’s an esteemed Senior Lecturer at Cornell University. But he’s also extremely active on, has many great embedded engineering lectures you can watch free-of-charge, and every year we look forward to seeing the projects — like this one — dreamed and realized by his students. Do you have final projects of your own to show off? Don’t be shy about sending in a tip!

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Microcontroller Lectures by Bruce Land

[Bruce Land] is no stranger to Hackaday as you can see from his profile, if you aren’t familiar with his work [Bruce Land] is a Senior Lecturer at Cornell University. One of the courses he teaches: Digital Systems Design Using Microcontrollers (ECE4760) was recorded in 2012 and again in 2015 and the videos are available on YouTube.

AVR to PIC32

[Bruce Land]s previous set of ECE4760 lectures (2012) used an Atmel ATmega1284 AVR Microcontroller for the laboratory portion of the course. This means the lectures are also based on the AVR and if you haven’t watched them through a few times you should do. The recently updated set of lectures is based on the Microchip PIC32, more specifically the Microstick II.

Open Curriculum

You can follow the ECE4760 rabbit hole as far as you want with all the available content provided by [Bruce Land] on his ECE4760 course webpage. You can watch the ECE4760 lectures on YouTube, try your hand at the homework assignments, and work through the labs at your own pace.

New Lectures = New Shirts

One area that [Bruce Land] is unmatched and arguably uncontested is his shirt collection, we are continuously impressed with these original works and wish they were available for purchase (wink/hint c’mon [Bruce] throw us a bone!). If you don’t know why the rest of us aren’t able to obtain the wonderful shirts [Bruce Land] wears you clearly aren’t subscribed to [Bruce Land]s YouTube channel, you should rectify that wrong and log some ECE4760 lecture hours starting with the video after the break.

Touch Piano Hits All the Right Notes

We love a good musical build, and this one is no exception. For their ECE4760 final project, [Wendian Jiang], [Hanchen Jin], and [Lin Wang] of Cornell built the nicest-looking touch piano we’ve seen in a while. It has five 4051 multiplexers that take input from 37 capacitive touch keys fashioned from aluminium foil and copper tape. Thanks to good debounce code, the sounds are clean even though the keyboard is capable of four-note polyphony.

A PIC32 and a Charge Time Measurement Unit (CTMU) module generate a small, steady current that charges up the keys. The PIC scans the pins continuously waiting for touch input. When human capacitance is detected, the value is compared with the base capacitance using the ADC and the sound is generated with the Karplus-Strong algorithm.

The group’s original plans for the project included a TFT screen to show the notes on a staff as they are played. While that would have been awesome, there was just too much going on already to be able to accurately capture the notes as well as their duration. Check it out after the break.

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Hardware Virtualization in Microcontrollers

Look at any sufficiently advanced CNC machine or robot, and you’ll notice something peculiar. On one hand, you have a computer running a true operating system for higher-level processing, be it vision or speech recognition, or just connecting to the Internet. On the other hand, you have another computer responsible only for semi-real-time tasks, like moving motors, servos, and reading sensors and switches. You won’t be doing the heavy-lifting tasks with a microcontroller, and the Raspberry Pi is proof enough that real-time functions aren’t meant for a chip running Linux. There are many builds that would be best served with two processors, but that may be changing soon.

Microchip recently announced an addition to the PIC32 family of microcontrollers that will support hardware virtualization. This addition comes thanks to the MIPS M5150 Warrior-M processor, the first microcontroller to support hardware visualization.

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Unix On Your Breadboard

As smartphones continue to get bigger and bigger, the race to have the smallest chip running Unix (or Linux, as the case may be) is still on. A new contender in this arena is [Serge] who has crammed RetroBSD on a Fubarino microcontroller for a powerful breadboard-friendly device.

The device uses a PIC32MX795 processor to run version 2.11BSD Unix for microcontrollers. It uses only 128 kbytes of RAM which is great for the limited space available, but it doesn’t skimp on software. It has a C compiler, assembler, and a whole host of other utilities that you’d expect to find in something much more powerful. All of this comes in a package that has breadboard-compatible pins so you can interface your Unix with the real world.

There’s a video below that shows the device in action, and a whole host of instructions that’ll get you up and running in no time if you have the hardware available. [Serge] mentioned that this would run on other architectures but is looking for others to join the project to port it to those processors. This isn’t the first time we’ve seen *nix installed on a microcontroller, but it is one of the more useful ones!

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Hackaday Prize Entry: A Pic32 Game Console

The official theme of the 2015 Hackaday Prize is to build something that matters. Solving the challenges facing the world is hard, and retro video games, despite what you read on Hackaday, do not matter.

That doesn’t mean there’s not space for the weird, esoteric builds out there; we have a best product prize that will dump $100k, a six month residency in the Hackaday Design Lab, and contacts with a lot of engineers with expertise in manufacturing. [Alex]’s extremely ow cost game console on a Pic32 is exactly what this prize category is looking for.

[Alex]’s project – XORYA – is based on the Pic32MX170F256, a chip that runs up to 50MHz, has 256kB of flash, and a full 64k of RAM. This is far beyond what the guys at Atari imagined back in the 70s, allowing the XORYA to have some amazing graphics.

Right now most of the build is dedicated to fleshing out the video system, and [Alex] has a great demo: rendering the Mandelbrot set in real time in 16 colors on an NTSC display with a resolution of 160×100. That’s a single-chip game console that’s right up there with the Uzebox, and a great example of the potential of the best product category for this year’s Hackaday Prize.

The 2015 Hackaday Prize is sponsored by:

3D Spectrum Analyzer uses 1280 LEDs

One of [Dooievriend]’s friends recently pressed him into service to write software for a 3d spectrum analyzer/VU that he made. The VU is a fairly complex build: it’s made up of 1280 LEDs in a 16x16x5 matrix controlled by a PIC32 clocked at 80MHz. [Dooievriend] wrote some firmware for the PIC that uses a variation on a discrete Fourier transform to create a 3D VU effect.

j6v2i When [Dooievriend] set out to design the audio analyzing portion of the firmware, his mind jumped to the discrete Fourier transform. This transform calculates the amplitude in a series of frequency bins in the audio—seemingly perfect for a VU. However, after some more research, [Dooievriend] decided to implement a constant Q transform. This transform is very similar to a Fourier transform, but it takes into account the logarithmic way that the human ear interprets sound.

[Dooievriend] started implementing the constant Q transform using an interrupt-based sampler, but he quickly ran into issues with slow floating-point math on his PIC32 (which doesn’t have a hardware floating-point unit). Thankfully he rewrote his code using fixed-point math, and the transform runs nearly real-time. Check out the video after the break to see the VU in action, and a second video that gives some details on the hardware build.

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