We’re starting to make a serious push at the sound programming for the Modular Music Box.

The audio hardware is a Rev. 1 Fluxamasynth, a bare-bones Arduino board hosting an Atmel ATSAM2195 General MIDI chip with rudimentary onboard effects. The chip interfaces to the Arduino via the standard serial-port library, which makes communication between the board and a host computer a bit of a problem: loading up Arduino sketches works fine, but the serial link is then used for MIDI. (The example code even brings up the link at the MIDI speed of 31.25 Kbaud, which might just be an in-joke; I very much doubt that the synth chip is opto-isolated!)

While it’s probably possible to get USB serial and MIDI serial communications running independently, that seemed like too much fiddling around. Since the Music Box relies on I2C for communication between its components, it made sense to bring up an I2C link between the Fluxamasynth and an Arduino Mega which I happened to have lying around. This was pretty much just a case of loading the Fluxamasynth with a basic sketch which passes all I2C bytes verbatim to the synth chip (I2C is 8-bit clean, so no armouring or wrapping is needed). The Mega uses a modified version of the Fluxamasynth “library” – in reality just a collection of MIDI message formatters – to put completed MIDI messages onto the I2C bus rather than serial. The breadboarding looks rather like this:

Yes, the power, ground and I2C lines to the Fluxamasynth are held in place by miniature G-clamps since I’m in no mood to try and solder up pin strips right now. (more…)

While the Auduino project provides plenty of code tweaks and hardware hacks to make an easy to use but versatile monophonic synth the Modular Music Box requires polyphony…

So I’ve been on a mission to try and find a suitable solution…

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I wanted to test the hall effect sensors I’d bought to see if they could be used for my idea of a rotary magnetic sequencer for the Modular Music Box.

There’s a link to the data sheet and a handy Hall_ Applications_Guide.PDF as well as some useful advice on the Sparkfun Hall Effect Sensor page and in the comments… and the Arduino:Playground provided a bit of code to test the sensor in action…

“You’ve got 3 pins from the front (the triangle edge). Left to right, power, ground, output.
Stick a 10k pull up between 5v and output. Then it’ll latch on/off depending on the poll you use.”

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The ‘Winder’ in the MMB has a ‘clock face’ of 12 orange LEDs in a circle used to give visual feedback on which way and how much to wind the key… as well as display the ‘winding down’ of the mechanism.

While I could have managed this by using an LED per digital output on the Arduino Duemilanove clone – I thought I’d use it as an opportunity to work with and learn more about LED drivers.

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The Rotary Encoder page at SparkFun has a datasheet, tutorials and additional info and advice in the comments:

• though medecau’s QuadEncoder Arduino library doesn’t compile…
• tronixstuff’s Chapter 11 section on the rotary encoder – and the code works well enough – though there’s a fair amount of ‘bouncing’…
• but with a little additional research I managed to get the Reading rotary encoder on Arduino example code to work – and it does seem to provide the most consistent and ultimately useful response to encoder input for my needs.

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While for testing purposes the Polymer Lithium Ion Battery – 2000mAh sku: PRT-08483 and LiPoly Charger – Single Cell 3.7-7V Input sku: PRT-00726 may do… further reading of Comments and datasheets suggests they may not be a final choice.

Cons

• ~6hrs charging a 2000mAh battery at 280mA max
• JST connectors can be *extremely* difficult to remove!

Pros:

• Battery includes built-in protection against over voltage, over current, and minimum voltage.
• useful 3 connectors – one to battery, one to circuit, third for 5V that powers the charger – so can charge the battery and power device at the same time.
• through holes in the PCB for remote LED

So looks like we’ll need something more like:

• LiPoly Fast Charger – 5-12V Input – sku: PRT-08293 – $19.95
• Polymer Lithium Ion Battery – 6Ah – sku: PRT-08484 – $39.95
• Wall Adapter Power Supply – 5VDC 1A – $5.95 – a 5V regulated power supply – although it has a US plug.
• Jumper Wire – JST Black Red – $0.95

which seems a bit expensive all in… particularly since we’ll require two battery packs – one in use and one on charge… (more…)

While worth buying to test the Adafruit Motor/Stepper/Servo shield and get some hands-on experiments done I suspected the Solarbotics GM17 might not be the best motor for the job(s) in the Modular Music Box – requiring +9V, having little torque at low speed and being quite noisy – though it is quite compact and did just manage to fit centrally in the monome size casing alongside an Arduino Duemilanove clone…

Further research suggested that a stepper motor would be the best choice to drive the sequencer and animation turntables. In the interim I tested a stepper motor from Fab Lab Manchester – the six wire PF35T-48L4 – a 7V (though it will supposedly run as low as 5V) 20ohms UNIPOLAR, S/A 3.6deg stepper motor. The makingthings.com Stepper Motor How-tos helped me identify the yellow and orange as one pair, the black and brown as the other and the red and green wires as the center taps.

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Before I emailed Pablo Gian Villamil and he sent me on a link to his class notes (yay!) for Generating polyphonic sound with Arduino I tried to work out his circuitry from his various blog posts and component listings…

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I bought a small 3-4.5V DC motor to start testing for the rotary magnetic sequencer I’m planning as part of the Modular Music Box for the Analogue is the new Digital exhibition as part of AND Festival…

Todbot’s Bionic Arduino: Introduction to Microcontrollers with Arduino: Class 3 has a section on Controlling a Motor using a 1N4001 ‘kickback’ diode and TIP120 transistor to “control speed of motor with analogWrite() just like controlling brightness of LED” which I still need to try out.

Then there’s a fairly thorough post at Lucky Larry’s ARDUINO, MAINLY ARDUINO PROJECTS, TUTORIALS… AND A FEW OTHER THINGS blog – Control a DC motor with Arduino and L293D chip… but (sigh)… I think I’ll just buy a shield kit.
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1. Visit the Leeds City Museum and discuss technicalities with Tom Pace, Senior AV Technician
2. Meet with Sue Ball from MAAP
3. Visit Leeds Parish Church for a practice bell ringing session and meet with Steve Ollerton, Tower Captain and the group
4. Visit other possible churches – time permitting…

Resulting in the following notes (they’re quite extensive – sorry):

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In setting up the Monomatic Flickr account I came across this existing  and unintentionally hilarious Monomatic listing on Flickr (part of the fantastic ‘Old Airport’ set in Mirsasha’s photostream)… look at the name badge – “Push to Flush” just has to be the name of our first album 😉

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