Highly Liquid Forums

Selecting LEDs & wiring them to the MIDI CPU

John — Fri, 03 Sep 2010 20:33:15 GMT

The MIDI CPU can drive just about any type of LED. But there are some things to think about...

Finding an LED that we like

There's obviously a huge variety of LEDs available. For LED indication, we want to look for the lower-brightness, lower-current types. There are more powerful LEDs used for things like flashlights, etc--not necessarily what's needed for indicator lights.

Indicator LEDs (or numerical 7-segment displays) typically work nicely at around 10-20mA of current or less.

Search for "LED" at Digikey and you'll get this page:

http://search.digikey.com/scripts/Dk...ds=LED&x=0&y=0

Under the "Optoelectronics" heading, click on "LEDs - <75mA, Discrete" and you get a nice parametric search:

http://search.digikey.com/scripts/Dk...t=524729&k=LED

Let's pick color=red, and mounting type = through hole. This narrows things down a bit.

We still have 40+pages of results to filter...so let's choose a Lens Type and Lens Style that we like.

"Lens style" round / 5mm / T 1 3/4 is the familiar, inexpensive plain LED. We'll choose that, and also "diffused red" for "lens type". Clear-lensed LEDs tend to have poor viewing angles.

Only six pages of results now. :) Check the "in stock" box, and we have only 2 pages, which we can browse by clicking the "View page" button.

Here's an inexpensive option with decent light output rating:

http://search.digikey.com/scripts/Dk...me=160-1705-ND

I'll use the above (LTL-307E) for the sake of example. But just about any regular (Vf = 2V +/- 0.5V) LED will work. Choose a color/size/shape that you like. :)

Determining how much current the LED will draw

Let's forget about the MIDI CPU and consider a single LED. An LED requires a series resistor to limit the current thru the LED.

Check out "Calculating an LED resistor value" here:

http://www.kpsec.freeuk.com/componen....htm#calculate

As stated in the link above, most non-super-bright, non-blue/white LEDs have a forward voltage of about 2V. Every LED datasheet will include a "forward voltage" rating.

Looking at the datasheet for our selection, we can confirm that Vf is 2V. The maximum forward current is 30mA, which is plenty. We'll probably operate the LED at 10mA or less, which is usually enough for a nice bright output.

The MIDI CPU can supply a 5V signal for driving LEDs. So, if our LED "drops" 2V (Vf = 2V), that leaves 3V across the current limiting resistor. If we choose a resistor value of 1kohm, the current thru the resistor (and thus, thru the LED) is 3V / 1kohm = roughly 3 mA.

Ok--3mA per LED. Let's take a look at how the LEDs are connected to the MIDI CPU. Here's an example from this thread:

Note that, instead of placing a resistor in series with every single LED, we can just place a resistor in each "LED Data" output line.

The MIDI CPU drives each "LED common" output in sequence, never more than one at the same time. Each LED Common output can drive up to 8 LEDs (as shown in the diagram above). If we have an LED matrix that includes a row of 8 LTL-307E LEDs with a 1kohm resistor on each LED Data output, then the MIDI CPU will be supplying up to ~24mA of current (3mA x 8) at any time.

This is within the 70mA that the Rev K MIDI CPU can supply. It is also within the 25mA per-control-terminal limit--this is important because a single "LED common output" control terminal will potentially drive 8 LEDs at once.

If our LED matrix had fewer LEDs per LED common output (in other words--fewer than 8 LED data outputs in use), then we could also use a slightly smaller resistor value and still be below the 25mA per-control-terminal limit.

More below...

Moose: MSA Configuration Utility for Mac & Windows

John — Fri, 03 Sep 2010 10:00:44 GMT

Blog Entry

The Moose Is Loose

wabbitguy — Thu, 02 Sep 2010 18:53:24 GMT

If you find it difficult or time consuming trying to work out the SYSEX for the MSA-P/R/T series decoders, this is to let you know that MSA Object Orientated Sysex Environment or "Moose" for short, is available for download from:

Wabbit Wanch Design

Moose will allow you to select your MIDI interface IN/OUT and channel and then show each of your MSA outputs so you can program each one individually.

Once you finish setting up how you want your MSA to work, you click the SYSEX SEND button, and your MSA is programmed. You can then use the Test button in MOOSE to make sure that your MSA works the way you told it to (which may or may not be the way you wanted it to).

You can also enter in values for the time lapse in ms or seconds to make timing issues a little easier to figure out. I.e. click in the edit field, wait til it highlights, type in the number of ms/secs you want. Send the Sysex.

Moose also remembers what the last SYSEX was that you sent to the MSA so the next time you run Moose it will display it to give you a starting point. Call it Moose Memory if you will...

There is an included Help file with the application that explains Moose's basic functionality but it's actually quite simple to use.

Moose is released as freeware from Wabbit Wanch Design for both Macintosh and Windows platforms.

Mel
Chief Executive Wabbit
Wabbit Wanch Design

Controlling MOTU audio interface and other rack hardware

ioplex — Tue, 31 Aug 2010 03:26:07 GMT

MIDI CPU a very cool product. Nice work.

I have an idea for a project but after just reading the hardware and firmware manuals it's not crystal clear that I can do everything that I want.

I will soon have a few 1U rack mount audio devices:

http://www.motu.com/products/motuaudio/traveler-mk3
http://www.lexiconpro.com/product.php?id=12

Many of the functions of these devices can be controlled using MIDI. The Lexicon reverb has a wonderful panel design but the MOTU audio interface has so much functionality (it's basically a digital mixer with lots of I/Os with filters and effects for each) that it requires digging around in menus or using MOTU's "CueMix FX" software. That's great but it really ruins the mood when your just trying to get into a jam on the guitar and then you have to navigate through a small LCD or reach for the computer.

So I would like to put one or perhaps a few MIDI CPUs into a 1U enclosure and use that to more easily access some of the more frequently traveled functions of these devices (the MOTU in particular).

First and foremost, I need a master volume knob / mute button that controls *all* outputs of the MOTU audio interface. The MOTU has a "master volume" knob but it only controls the primary outs (such as analog 1-2). I intend to have 5 studio monitors and a woofer (analog 1-5) for watching media with surround sound and thus that "master volume" knob will have no effect on the other 4 speakers (center, woofer, rear left and rear right). So if you get a phone call while you're watching a movie you basically have to stop it.

I don't have the MOTU manual in hand so I'm not sure yet if all analog out faders can be controlled by MIDI. But assuming they can, it seems I could connect one pot to 6 analog control terminals on the MIDI CPU and configure them to send the required CC to control all 6 analog out faders together. That would give me a proper "master volume" control. If it was also the push-toggle type, that could double as a mute switch.

However, from reading the firmware manual I anticipate a few possible problems. If the fader values required by the device are not in the rage 0-127, I need a way to scale the CC values. I could use CC number remapping but this means I could not use that MIDI CPU for any other CC controls.

Also, regarding the mute feature, I could use 6 CC toggle mode logic inputs but it is not clear to me how I can restore the volume level when the mute button is un-toggled (although I suppose simply moving the volume pot slightly will restore it). The manuals elude to using Multipurpose Data when emitting MIDI events but after one pass through the documentation it's not crystal clear to me how to use it.

Secondarily, if I'm going to use 1U of space for this project, I might as well have a few extra controls aside from one big master volume / mute knob. In particular, I would love to copy the "PROCESSOR 1/2" part of the Lexicon MX200 panel design. Here's a big graphic of the front panel:

http://www.lexiconpro.com/images/pro...2/large/30.jpg

Each of the two processors on the MX200 have an Effect Select switch, a Bypass switch and three pots which control parameters that depend on the selected effect.

It would be fabulous if I could switch between multiple independent MIDI CPU configurations. Then the pots will send three different CC events depending on the selected configuration. One could be used to control eq on one of the preamp inputs of the MOTU audio interface. Another might control compression settings. Etc. I realize layers cannot be used for this but the concept of layers is close enough that it makes me wonder if the desired functionality could be added in a firmware update.

Mike

PS: I'm a C programmer, compute my taxes in hexidecimal and I have piles of EE gear in the basement so feel free to shoot straight.

a question about analog inputs

technician4 — Mon, 30 Aug 2010 19:00:06 GMT

hi,

i have a quesiton regarding just what i can attach as an analog input. my midi cpu install will include 3 encoders with integrated push button switches, the grayhill 25LB22-H for channel selection, and i was hoping to include inputs for a clock output from a grendel drone commander as well as the gate and CV output from a x0xb0x.

the grendel clock signal is a square wave signal which ramps from 0 to 8-9V at its slowest oscillation, and ramps from 0V to as low as 1-2V at its quickest. i'm no electronics wizard, but i've been able to clamp the signal to 4V at its peak with a small zener diode circuit, so it won't exceed the maximum Vreg (which will be 5V if the box will be running off a 9V battery?). the three questions i have about this particular input are: is it acceptable as an input to begin with? given that the signal can drop below 3.3V does this pose a problem? i haven't poured over the firmware manual all that well yet, but, given the peak voltage is not consistent can the midi cpu be configured to listen for a certain minimum, somewhere between the 0V and 4V it will receive on that channel?

with respect to the x0xb0x, i realize it already has midi integrated, but if i wanted to use the CV out to map to another parameter within a program like pure data, could the midi cpu accept the signal without any modification before the terminal input?

the x0x clock out is quite high and would need to be clamped like that of the grendel, would its configuration be much different from the previous one given the signal here is consistently the same peak voltage?

i've rattled this off quickly and hope i've been clear, thanks very much!

transpose

rhaley — Sat, 28 Aug 2010 17:52:48 GMT

HI John,

Can you confirm for me...can I put a 12 way rotary switch on the midi CPU to transpose up a semitone (+6) and down semitones (-5)

and of course, what sys ex message would this be?
Thanks

Firmware 1.3 Features Discussion

John — Fri, 27 Aug 2010 16:35:12 GMT

Firmware 1.2 is now the "current" version and is shipping on each newly purchased MIDI CPU. The firmware update sysex & manual are available on the product page.

Here's a few things that I'd like to add to version 1.3. This is preliminary and I'm not guaranteeing that anything will be included.

- Some basic "MIDI filtering" functionality. In other words, the option of taking MIDI input and changing it before sending it thru as output. Things like note transposition, transforming notes to CC commands, clock division, etc.

- Allowing configurable matrix polarity. Some key matrices have "diodes pointing the wrong direction". Although there are already ways to accommodate this (with note remapping)--it would be more efficient in some cases to have "high" select pulses rather than "low" ones.

- Allowing multiple config layers for matrix select outputs. This would allow more efficient use of control terminals. It would also be useful for a project like this: http://forum.highlyliquid.com/showthread.php?t=315

- User configurable maximum value for register increment modes. A finer point for use in things like foot switch controllers.

- A "note hold" function for continuous note generation.

There are lots of other items on the "wish list"...when I start working on things, I'll get a better feel for what exactly should go in.

MIDI CPU Firmware Version 1.2

John — Fri, 27 Aug 2010 09:35:08 GMT

Blog Entry

Piezo Trigger Wiring Strategies

John — Wed, 25 Aug 2010 21:53:16 GMT

Each MIDI CPU control terminal can accept input from a piezo trigger. Several wiring methods can be used.

The easiest method involves a simple NPN transistor circuit:

Here are the specific parts I have used:

Piezo Element: http://search.digikey.com/scripts/Dk...127-nd&x=0&y=0
Rb = 220kohm
Q1 = KSP13 (Darlington)

The above circuit works pretty well. However, there are some drawbacks. Sometimes, a gentle strike to the piezo element generates a pulse which is too short to be detected by the MIDI CPU.

Also, if the piezo element is subject to a different kind of pressure--say, a slow, gentle finger press instead of a "staccato" strike, multiple on/off pulses can be generated, with corresponding MIDI messages.

To avoid "missed hits" and "double hits", we can groom the trigger signal with a 555 timer circuit as shown below:

The 555 timer is operating in "monostable" mode, which means that it generates a fixed-length pulse whenever the trigger input goes from high to low. The values of C1 and R1 determine the pulse length. There is tons of 555 timer info on the web if you want more information about how that works.

I used the values C1 = 2.2uF and R1 = 220kohm for a pulse length of roughly half a second.

This means any strike, even a soft one, will result in a 0.5s pulse from the 555 timer (and to the MIDI CPU control terminal). If the piezo generates "multple hits" within 0.5s, they will not result in additional MIDI messages.

Adjustment of R1 (say, by replacing it with a potentiometer) will allow us to adjust the pulse length.

Any pulse longer than a few ms should give the MIDI CPU plenty of time to "notice" the input activity. The triggering works very well with a ~4ms pulse from the 555 timer. (C1 = 2.2uF; R1 = 1.5kohm)

Controller building advice. (Encoders & LED Indication)

The19thbear — Mon, 23 Aug 2010 17:57:12 GMT

Hi. I am thinking about building a controller for a specific plugin i Use alot.

It needs to have midi in/out. If i make a change to the gui on the plugin it has to be show on the controller via encoders with LED rings and buttons with LED's - just like a normal controller (like the behringer bcf2000 for instance)

Here are the specs of what i need:

-30 encoders/pots with led rings (about 16 LEDS per pot would do)
-19 buttons with 3 states (should function like a normal analog switch with 3 modes - up/middle/down) and 3 LEDS per button. - each time the button is pressed it goes down a level ( goes from up to middle to down per button click)

-Anybody made anything remotly similar to this?
-can it be done with the MIDI decoder and MIDI incoder? - im guessing i have to use 3x encoders and decoders because of all the buttons/pots.
-will the whole - send plugin info to controller via LED rings, work? and does it need any special diy board?

- im planning on butchering a bcr2000 and using the encoders with led rings.

Thanks alot people!

basic midi controller with pots

meech — Sun, 22 Aug 2010 16:45:17 GMT

Hi
I have some basic questions before i buy the pots.

1.Reading the hardware manual i see that the suggested pots should be between 1k and 10k. Is one better than the other for this ?

2. the control wiring page on the manual shows that 14 pots can be added to the cpu. ... correct ?

:cool:

i just plan to put it in an aluminum project box with as many shiny aluminum knobs as i can fit on it to control the filters and pitch on my emu e6400 sampler.
thank you.
d

Output modes request

GroovingNoise — Sun, 22 Aug 2010 13:49:02 GMT

Hi, John.

Great products!:)
Your products will bring us great experience of MIDI.
To get even more controllabilities, I strongly suggest some output modes.

These modes are "common" behavior of the MIDI equipments.
Since there are many MIDI Controllers which have the ability to send only PC and CC,
these modes will be very useful.(Maybe desired by many)
__________________________________________________

1. Controller (CC) Latch mode [ ss : Controller number (hex) ]
Output is "off" for Corresponding CC Value 0 - 63
Output is "on" for Corresponding CC Value 64 - 127

2. Controller (CC) Inverted Latch mode [ ss : Controller number (hex) ]
Output is "on" for Corresponding CC Value 0 - 63
Output is "off" for Corresponding CC Value 64 - 127

3. Controller (CC) Toggle - Initial state "OFF" mode [ ss : Controller number (hex) ]
Corresponding CC toggles the switch.
CC Value will be ignored.(Any CC Value will toggle the switch)
The initial switch state is OFF(open).

4. Controller (CC) Toggle - Initial state "ON" mode [ ss : Controller number (hex) ]
Corresponding CC toggles the switch.
CC Value will be ignored.(Any CC Value will toggle the switch)
The initial switch state is ON(close).
One of the usage of this mode is using together with "initially OFF toggle mode",
to achieve linking different state switch.

5. Controller (CC) Group switch mode [ ss : Controller number (hex) ]
The overall behavior will be like the toggle mode.
(Corresponding CC toggles the switch, CC Value will be ignored.)
But this mode will allow grouping more than 3 switches.
Only one switch within a group can be ON at a time.
By turning a switch ON, all other switches in a same group will turn OFF.
It also can be all OFF by sending the CC which corresponds to the switch currently ON.
The mm value will mean a group.
Maybe 2 groups are enough because this mode is worth when grouping more than 3 switches.

6. Controller (CC) Fixed Length ON pulse mode [ ss : Controller number (hex) ]
Corresponding CC triggers a fixed-length "on" pulse.
CC Value will be ignored.(Any CC Value will trigger the pulse)
Pulse length is specified by ph and pl.

7. Controller (CC) Fixed Length OFF pulse mode [ ss : Controller number (hex) ]
Corresponding CC triggers a fixed-length "off" pulse.
CC Value will be ignored.(Any CC Value will trigger the pulse)
Pulse length is specified by ph and pl.

8. Controller (CC) Fixed CC# mode [ ss : Responding Bit (0-7) ]
Responds CC# & CC Value.
The CC# act as Bit0, the CC Value act as Bit1-7.
So, we can toggle all 8 switches with 1 CC message.

CC# must be factory-defined two numbers.
Other CC# will be ignored.
For example, 80 & 81 at this time.
(Needless to say it's great if you can offer user the capability to program these 2 numbers.
But it may require new message format. So, I think it's not easy to add...)

The ss "Responding Bit" is just an option.
Usually, they will be the switch numbers.
But will bring something when cascading some MSAs especially.
Or for some tricky usages.

For example:

Configuration: Responding Bit = sw# (each)
( sw0 -> bit0, sw1 -> bit1 ... sw7 -> bit7 )

CC#: 80, Value: 0 -> 00000000 = all OFF
CC#: 80, Value: 1 -> 00000001 = all OFF, except sw7 is ON

... (An omission) ...

CC#: 80, Value: 126 -> 01111110 = sw1-6 are ON, sw0,7 are OFF
CC#: 80, Value: 127 -> 01111111 = all ON, except sw0 is OFF
CC#: 81, Value: 0 -> 10000000 = all OFF, except sw0 is ON
CC#: 81, Value: 1 -> 10000001 = sw1-6 are OFF, sw0,7 are ON

... (An omission) ...

CC#: 81, Value: 126 -> 11111110 = all ON, except sw7 is OFF
CC#: 81, Value: 127 -> 11111111 = all ON

CC#: 82, Value: 0 -> NOT RESPOND

9. Program Change (PC) Fixed PC# mode
Responds PC# with defined behavior.
This mode is not 1 switch setting but "GLOBAL" setting.

For example:

PC 0 -> sw0 ON
PC 1 -> sw0 OFF
PC 2 -> sw1 ON
PC 3 -> sw1 OFF

... (An omission) ...

PC 14 -> sw7 ON
PC 15 -> sw7 OFF
PC 16 -> sw0 toggle ON/OFF
PC 17 -> sw1 toggle ON/OFF

... (An omission) ...

PC 23 -> sw7 toggle ON/OFF
PC 24 -> sw0 ON Pulse

... (An omission) ...

PC 31 -> sw7 ON Pulse
PC 32 -> sw0 OFF Pulse

... (An omission) ...

PC 39 -> sw7 OFF Pulse
PC 40 -> sw0 ON/OFF Pulse

... (An omission) ...

PC 47 -> sw7 ON/OFF Pulse

The ON Pulse will require the "OFF" state. Or the PC command will be ignored.
The OFF Pulse will require the "ON" state. Or the PC command will be ignored.

The ON/OFF Pulse will trigger the pulse that is opposite to the current switch state.
i.e.
When the switch state is "OFF", it will trigger the ON Pulse.
When the switch state is "ON", it will trigger the OFF Pulse.

10. preset mode
Maybe needless to explain;) The preset will be called by PC command.
__________________________________________________

I'm sorry for the LOOOOONG post.
I hope you will get some inspiration from this.

MIDI CPU Activity?

Tye P — Sun, 22 Aug 2010 11:38:15 GMT

Hi,

I am building a MIDI controller using the MIDI CPU and some SPDT switches. Later down the line it will be connected to the MSA-R converting my MIDI signal back to voltage. (Basically voltage to MIDI back to voltage).

Anyway, I have built the MIDI controller, but my hope was that when my switch was pushed in (i.e. closed switch) the MIDI signal would be constant (not just a single closed switch message). Is this the case?

The only reason I am guessing that it is a single message is by the Activity LED. If it were a constant message, would not the Act LED stay constantly lit while my button is down, and when the button is released (open switch), the light would turn off?

Or is there anyway to wire the MIDI CPU so that when the switch is closed, it is constantly sending MIDI messages? (Only because when it is finally connected to the MSA-R, I want it so that when the switch is pushed in, the relay stays open, and when the switch is released, the relay closes).

Sorry if this doesn't make sense, that's why I'm asking for help.

Thank you,

Tye

what i'm hearing...

technician4 — Thu, 19 Aug 2010 02:46:07 GMT

hi,

just finished assembling and installing the midispeak kit, and was hoping to get a little clarification. first off, i apologize in advance for not having fully, properly tested the installation, but i'm too curious for the answers and haven't had time to get back into the workshop.

i installed for rom mode operation, and when i send note ons (and corresponding offs) it really sounds like i'm hearing more than one fragment at once. is it possible that without sending the CC message i'm actually hearing more than one bank at once?

the other more broad question is, does rom mode give me access the individual, programmed allophones, or to larger fragments than that?

thanks for looking

Software Beta Testers Wanted

wabbitguy — Wed, 18 Aug 2010 23:01:29 GMT

I've written a Macintosh application to aid in programming the MSA-R, T and P series decoders. So I'm looking for anyone who is interested in testing out the software on an R, T, or P unit.

I only need four or five people maximum to help with testing.

if you're interested, send me a private message with a valid email address you can be reached at, I'll email you all the additional information at which point you can decide if you're at all interested.

I'll also mention that at the end of the testing cycle, the software will be posted on my web site and free to all Mac users. Thus it's not like you'll be saving any money by becoming a beta tester.

For the skeptical who think I'm trolling for email addresses, I've already discussed this with John, who okayed it so I'm not spamming or trolling. You can check with him if you have any doubts.

We now return you to your regular bit twiddling SYSEX program...:D

Mel
Wabbit Wanch Design