Reading from a large number of inputs, like this piano keyboard, can be tedious. Even when multiplexing there’s a lot to keep track of. But if you choose the right microcontroller, you may have hardware assistance. Here’s an ATmega640 is using it’s external memory interface to read the key matrix.

You may remember the Open Music Labs article about reading from a shift register using just one pin of a microcontroller. This time around a shift register is still used, but instead of pulling in a long line of parallel inputs, the switches are multiplexed to reduce the number of I/O pins used to read them.

A 74HC573 is used to facilitate the multiplexing. We won’t go into how that part is accomplished; there’s a separate post that explains the process. What’s unique here is that the XMEM peripheral of the AVR microcontroller is used to grab the data. This is intended for external memory chips, but if you get the timing just right, it greatly simplifies reading in a matrix of up to 128 inputs.

Here’s an interesting article about reading data from shift registers using less than three pins. 74HC165 shift registers are a popular choice for adding inputs to a microcontroller. They have a parallel input register which can be read using the latch, then shifted into a microcontroller via the data and clock pins. For those counting, that’s the three pins normally associated with driving these devices.

This hack first does away with the latch pin. The addition of a carefully trimmed RC circuit (capacitor is charged by the clock pin, then the resistor lets that cap slowly discharge) means that the device will not latch until after the clock stops toggling. This technique drops the control down to just two pins (data and clock). You can still use hardware SPI to read the data using this method. It’s the same as using SPI to drive 595 shift registers except the microcontroller reads data instead of writing it.

But wait, there’s more! The diagram above actually shows a way of reading this shift register with just one pin. Notice that the clock and data pins are now connected to just one of the microcontroller pins. The data pin has an added resistor, which keeps the current low enough that it will not compete with the clock signal coming from the microcontroller. In between clock pulses, the microcontroller switches from output to input to read the data pin on each cycle. Give it a try, it’s a fun experiment!

Workshop 88 member [Jim] got his hands on a couple of SanDisk Sansa Clip+ MP3 recorder/players from Woot, and was anxious to see what he could do with them.

The first order of business was to install RockBox, an open source hardware package built for a wide range of MP3 players. He was impressed with how robust the firmware was, though he thought the Sansa’s built-in microphone could use a bit of upgrading. Acting on a tip from a fellow square dance enthusiast, he disassembled one to see how he might add an external audio input.

He pried the existing mic apart, and desoldered it from the motherboard, installing a small capacitor and resistor in its place. He extended some wires through the case, then powered up the unit to make sure it was still alive and well. Since things still looked good, [Jim] put some audio on the Sansa’s new inputs and sure enough it recorded the audio without a hitch.

He says that his initial guesses for the capacitor and resistor values were pretty decent, though with a bit of tweaking he should be able to get exactly the recording levels he was looking for. Not bad for a $20 audio recorder!

[Kalin] loved the picture from his new Samsung HMX-T10 camcorder, but the sound quality didn’t match up. Since it records video that can be directly imported to his editing suite of choice he didn’t want to just buy a different model, so he cracked it open and added an external mic input.

As with most consumer electronics these days, the hardest part of the hack is getting the thing apart and assembling it without any damage. [Kalin] had to get down to the bare circuit board to get to the audio input connections. He soldered up some shielded extension wire to an audio jack, then made some space in the case by cutting a bit of the plastic structure before finally gluing it in place. Details are a bit scarce, but it looks like he wired up the jack along with a couple of switches. We’d wager this still lets him use the stock microphone if he doesn’t feel like hauling around extra gear.

You can buy nice audio breakout equipment for your iPod if you don’t mind breaking the bank. This is partly because the demand is not incredibly high so commercial breakout hardware doesn’t benefit from volume discounts. But it’s also because Apple charges licensing fees for third-party accessories (often referred to as the “Apple Tax”). [Reed Ghazala] decided to side-step the whole situation by building his own accessory which he calls the iPad Audio Desk.

It all starts with a breakout board. The PodBreakout Mini provides an easy to solder interface for the iPad, and ensures that the repetitive act of plugging and unplugging the connection doesn’t break a solder connection. From there [Reed's] enclosure finishing skills take over. The shape and curve of the aluminum sheet give the look befitting an expensive tablet device. Along the back you can see the jacks for line-in, line-out, video, mic/guitar, and headphones that make the dock useful. It wouldn’t be hard to make one… but it might be hard to make one look this great. See for yourself after the break.

Needing to test the display interface for a multitude of different sensors [Fileark] built himself this analog and digital input/output simulator. Along the bottom is a double row of trimpots that adjust analog voltages. Each voltage is measured by the Arduino inside and its value is displayed on the graphic LCD screen to confirm that the hardware you’re testing is making correct measurements. There’s also digital I/O in two different forms. To the upper left are momentary push buttons but the DIP switch bank below that allows the same connections to be toggled on and off. It’s not an automated test bed, but if you’ve got a lot of I/O, or a lot of hardware to test this will save you some real time.

Don’t miss the demonstration video after the break.

[Nali] is fixing up a 1966 Rambler Ambassador and decided to give the audio a bit of an upgrade. Instead of replacing the head unit he added a connector for audio input. The method he used is simple, inexpensive, and allows the original unit to continue functioning as a radio. He cut the feed wires going to the volume knob and patched in a headphone jack. The jack he used has an internal switch that is meant to switch off a pair of speakers when headphones are plugged in. The jack will allow the original signal from the radio tuner to pass through whenever there isn’t a connector plugged in. It seems like this is easier on older hardware than it is on modern equipment.

This isn’t where his entertainment enhancements stop. [Nali's] working on a 7″ in-dash Linux machine so keep your eye on his thread to see what he comes up with.

[Thanks Joel383]

Tape decks in cars? Yes, that used to be quite common before optical media took over road. [Nirav Patel's] 2004 Toyota Corolla had a deck that he used with a tape adapter in order to listen to music from his iPhone. But one day something happened and, although the adapter still worked, the cassette player started making distracting noises. [Nirav] set out to quiet the noise and install an auxiliary audio input for the sound system. There were some tripping points along the way, like breaking everything and starting a small fire, but perseverance got him to his goal. Because these units are built with compatibility for things like CD changers they have a communications bus called AVC-Lan. This protocol has been sniffed out and documented, and [Nirav] even found an existing audio-input hack that he based his design around. Now he’s able to plug directly into the dash and ditch the cassette adapter.

We’ve seen [Nirav's] work a few times before. He’s shown us a first person shooter controller and his site was a resource in our Launchpad programming with Linux post.

[via Make]

This two handed glove input setup, by [Sean Chen] and [Evan Levine], is one step closer to achieving that [Tony Stark] like workstation; IE, interacting with software in 3D with simple hand gestures. Dubbed the Mister Gloves, the system incorporates accelerometer, push button, and flex sensor data over RF where an MCU converts it to a standard USB device, meaning no drivers are needed and a windows PC can recognize it as a standard keyboard and mouse. Catch a video of Mister Gloves playing portal after the jump.

While amazing, we’re left wondering if gesture setups are really viable options considering one’s arm(s) surly would get tired?

This one could be a game changer. [Chris Harrison] and a team of researchers are showing off a method of using your arm as an input device. An arm band worn by the user picks up acoustic signatures created by tapping on your arm with the other hand, or taping your fingers and thumb together on the same hand. They’re achieving accuracies in the 82-97% range but it gets even better. Take a look at the video after the break and see what they’ve done by adding a pico-projector to the arm band in order to use your arm or hand as a touch display.

We liked seeing the concept mice from October, but the future of input devices might already be attached at the elbow.

[Thanks Wilfite via BBC News]

USB is convenient and that makes it desirable in many many projects. [Simon Inns] has the process down and is sharing it with his recent PIC based USB tutorial. Prompted by requests for help on the matter after having published a post about his Commodore 64 interface, he set out to detail the particulars when it comes to using the PIC 18F family as USB input devices. This example uses a PIC 18F4550 with the circuit built on a breadboard. There’s not much required here, an oscillator, a few passives, and a USB B connector. The magic really happens in the code. Take a look at this well-written guide and give it a try with your next project.

Don’t need USB? [Simon's] game hack, the Ultimate Simon is always worth another look too.

This new video about [Pranav Mistry's] SixthSense project doesn’t bring us much that we haven’t seen before. At least, not on that project. What really caught our eye was the device he shows off at the beginning of the video. Using two old ball mice, he constructed a grip style input device. It is simple and elegant and we can definitely see using this in future hacks. Not only is it cheap and apparently effective, it seems as though it could be constructed in a very short amount of time. all you need are the wheels that spin when the ball moves, 4 springs and some string. Why didn’t we think of that?

[thanks Sean]

What happens when you combine an IR tracking PS3 Eyetoy, and a high-resolution projector? If you answered multi-touch display, you’re on the right track. Add a Wii Nunchuck controlled robot, a pinch of Community Core Vision tracking software combined with Processing, and the piece de resistance, a modified Memo TUIO particle system and you get the mesmerizing video above.

Check out this combination of crazy robotics and more with SparkFun’s free robot hobby builders meet-up on Saturday.

[Thanks Anon]

We’re not sure why [Roteno] prefers to have his TV and cable boxes not face him when he’s sitting on the couch, but to each their own. You may already see many problems with this setup: discoloration from LCD viewing angle, difficulty playing Wii, oh and most importantly – not being able to change the channel with his IR remote. [Roteno] was lucky enough, however, to have an IR remote input on the back of his cable box. All it took was a 3.5mm jack and a spare IR receiver and he was back in business. Sure it’s not as technical as some of our cable or IR hacks and we would like to see someone try this who doesn’t have as easily accessible IR input on the back of their cable box. But either way, here’s one more step to never having to leave that couch.

[Judyofthewoods] has hacked together this rollerbar mouse. We’ve heard people talk about these in a positive way, going on about how comfortable they are. We haven’t really experimented with one much to verify. This one looks surprisingly nice considering it is made from scrap. The image above is showing it without the cover that hides the hot glue and optical sensor. There isn’t much of a writeup, but as you can see from the picture, there isn’t much necessity for one either.  She seems to have done a great job stating that it is fairly smooth with only minor jittering.