Sending LED colors to APC-MINI MK2 using System Exclusive (SysEx)

Hi. This maybe of interest to this thread. According to this guide (p9) the pad colours can be customised by RGB values using sysex.…/APC%20mini%20mk2%20…

‘RGB pad colors can be customized using SysEx commands. This message is sent to the device to set one or several of the unit’s RGB LEDs to a specific color. The color is created by sending three 8-bit color values for each color component (Red, Blue and Green). Standard MIDI only supports 7-bit messages, so each color in the RGB Color Lighting message will be expressed using MSB/LSB.’

What that all means in practice is way above my head but I am thinking of creating a translation where I take the usual ch/note/velocity info and change what colour it outputs using sysex. Basically customising the colours to my own liking. I just don’t know how to intepret the sysex documentation into practice.

Yes, I saw that in the manual. In reality this is probably over most people’s heads and I’m not really sure how good the color resolution is of the LED’s. Total of 16383 of each red, green and blue values would be a lot to ask for for a low cost LED. My guess is that the LSB’s are not going to show much difference and maybe just 2-4 high order bits of the MSB’s will.

I can show an example if you really want to explore this further.

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

I am interested. I wonder if it would be complicated to do a test project where Akai faders simply change all the rgb values to test how the pads LEDs actually render colours. That could also help me unpack what the sysex would actually look like too. But I confess it is way over my head as to where to start and how complicated it could be. I’ve never actually created a sysex message though I’ve been using MIDI since the 80s.
Obviously accept it won’t be the full resolution of 8bits, but rounded to match values, but hey, we do 128 midi values to 255 DMX all the time, don’t we? :slight_smile:

My ultimate goal will be to convert DMX RGB to pad LEDs RGB.

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Hi, please show the below example.

I use the first 6 faders to designate MSB and LSB values for red, green and blue.

Faders 1 and 2 hold red MSB and LSB
Faders 3 and 4 hold green MSB and LSB
Faders 5 and 6 hold blue MSB and LSB
I use global variable gb to hold the value of red, gc to hold the value of green and gd holds the value of blue.

In Preset 0 (Init) translator 2 (0.2). I set the initial values. I also set the target note (LED) number.

Translator 1.1 handles all of the fader manipulation and note values. I determine by fader which color to manipulate within the rules. Warning… they are likely too
complex for most users to understand at first but essentially I have to only update a portion of gb, gc, or gd since faders handle only 128 values and as I said earlier using MSB and LSB values together you get 16384.

As it turns out, it appears that only bit 0 of the MSB is used by the APC-MINI MK2 so essentially it recognizes only values of 0-255 with the MSB only being a 0 or 1. I didn’t find this out until after I completed and tested the project.

Translator 1.0 output is ‘Perform’ with the parameters of:

  • Note Number
  • Red Value
  • Green Value
  • Blue Value

Translator 1.1 takes these values and the splits them of to send a raw MIDI message using System Exclusive (SysEx)

I use aliases as in my case I’m using named virtual ports instead of the actual device but I did test it with the actual device. You will need to point them to your actual controller.


You can learn more about aliases from this tutorial.

Also I set up my device management at the preset level.

For more information about device selection, see this tutorial.

If you open the MT Pro log window, you can see more information on what is happening.

apc-mini-mk2-color-control.bmtp (4.0 KB)

Happy learning!

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

Hi Steve,
Wow. Thanks. This is very interesting and helpful and pretty dang cool.

This is how it seems on application as well. The MSB is essentially toggling the LSB between the lower range and upper ranges of brightness. Even values=lower - Odd values=upper. I’m going to attempt to put each colour on a single fader, albeit with lower resolution. If I can do that, then it will be fairly straight forward to control the pad colours via DMX over ArtNet.
I’m attempting to deconstruct your maths and in doing so, learning lots.
Thanks Steve.

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Hi Steve,

I tried to modify to use just one CC(fader) per color. Using this basic math.

If CC value (qq) =<63
MSB = 0
LSB = qq*2
(ie lower range 0-126)

If qq >63
MSB = 1
LSB = pp*2-127
(ie upper range 1-127)

My math is good but the execution in the preset is terible :(. I realise, as I expected, I’m in way over my head.
apc-mini-mk2-RGBcolor-control_singlefader.bmtp (3.8 KB)

Though I will persist. Any advice is appreciated though.

You cannot send a MIDI value out more than 127 which is why they break it up in 2 bytes. Anything higher than 127 indicates a control byte. Best to just deal with MSB always 1 and use values 0-127 for the color values. Of course since DMX allows for 8 bits (value up to 256) so there will need to be some way to convert to 8 bits on your DMX lighting system.

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

I change the project as follows

MSB and LSB are always the same value. We put them both based on the value of incoming LSB

Since even numbered LSB always turn the LED off, I made the output always put out odd numbers except for 0 when we truly want that color off

The above were handled in the rules and output of translator 1.1

New Rules:

// fix red
if pp==0 then skip next rule
if tt==0 then pp=pp+1
// fix green
if qq==0 then skip next rule
if tt==0 then qq=qq+1
// fix blue
if rr==0 then skip next rule
if tt==0 then rr=rr+1

On output I put out LSB value for both MSB and LSB

Output Sysex

// Header
F0 47 7f 4f 24
// Number of bytes MSB
// Number of bytes LSB
// Start Pad
// end pad
//red msb
//red lsb
// green msb
// green lsb
// blue msb
// blue lsb
// Footer

On the input of 1.0, I mapped the faders so that the first 3 faders would handle the color mapping. This is a kludge so that I didn’t have to modify the rules below which were hardcoded to certain incoming fader values.


if pp<48 then exit rules, skip Outgoing Action
if pp>50 then exit rules, skip Outgoing Action
// Kludge added So that consecutive faders work
// First 3 faders to match rules below
if pp==49 then rr=50
if pp==50 then rr=52

The rest of the rules below that, I didn’t touch.

Now the first fader handles red intensity, the second fader green intensity and the third fader blue intensity.

apc-mini-mk2–single fader-color-control.bmtp (4.2 KB)

In reality we could simplify by changing the whole translators to follow similar logic and remove a lot of rules that are no longer applicable. I just don’t want to go there right now. :wink:

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

And then I decide to just create a more simplified version.

It still baffles me why even numbered values turn the LED color off and I have to use only odd numbered values. To me it looks like the manual is not 100% accurate.

apc-mini-mk2–single fader-color-control-simplified.bmtp (2.9 KB)

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

This one is even better. I basically double the value of the incoming message.
Since the max value is 254, I add 1 to that to get the full scale. This is done in translator 1.0

if pp<48 then exit rules, skip Outgoing Action
if pp>50 then exit rules, skip Outgoing Action

// scale it
if qq==254 then qq=qq+1
Log "Scaled value is %qq% Original value is %tt%"

if pp==48 then gb=qq
if pp==49 then gc=qq
if pp==50 then gd=qq

Label "done"

// perform paramters
// ww is note number
// gb is red value
// gc is green value
// gd is blue value

Then I break apart into MSB LSB in translator 1.1

// from page 9 of the APC MINI MK2 Communications Protocol
if zz!=0 then Log "Log note %oo% red=%pp% green=%qq% blue=%rr%"
// fix red

// fix green

// fix blue

The document is accurate, it was just my brain that was off :wink:

apc-mini-mk2–single fader-color-control-simplified-better.bmtp (2.9 KB)

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:


I’m just catching up on these and away from my system to load this up but keen to do so.

My thoughts on next step are to map running CC#s to running Note Numbers (Akai Pad)/R, G & B. (with initial offsets)

|CC#1 | ww (note) 1 | Red (0)
|CC#2 | ww (note) 1 | Green (1)
|CC#3 | ww (note) 1 | Blue (2)

|CC#4 | ww (note) 2 | Red (0)
|CC#5 | ww (note) 2 | Green (1)
|CC#6 | ww (note) 2 | Blue (2)


the math for the numeric base would be

pp (CC#)

ww= 'ceil(pp/3)` (note number)

Colour= **pp mod 3** (0=gb(red), 1=gc(green), 0=gd(blue)

where ceil is the ceiling function that rounds up to the nearest integer.
where mod is the modulus operator that finds the remainder after division.

Is that type of math possible in BOME?

I have various means of converting DMX (ArtNet/SACN) Channels to MIDI CC, so if the above could be achieved in a single pass-through it would be straightforward to control all of the LEDs from a lighting controller or software. Each pad=1 Fixture (Generic RGB). That would open up a world possibility for keeping the pad colours in sync with the console… any console.

Well you only have 9 faders on the APC-MINI so you would only be able to handle 3 LED’s. Maybe use an outer button to switch layers so that the faders can be re-used for a different purpose for each layer.

Bome MIDI Translator only uses unsigned integers. There is no floating point so you would need to do integer math. There is a mod operation (%), however, and so with that it would be possible to do a combination of integer match with the MOD operator. First we should figure out exactly how you want to control each LED and/or manage layers.

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

Oh and if you are controlling with your lighting console instead of your faders, you have 64 notes in the matrix so would need 192 CC’s so you still would need to bank using different MIDI channels or similar to control all 64 notes. There are only 128 CC’s available per channel and I wouldn’t recommend using those that are designed by MIDI standards that are intended usually for other purposes.

Maybe each row of LED’s you use a different MIDI channel to control.

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

This should help with your calculations. Press lower left button on your APC-MINI (Note 0) and view the log window.

Look at the rules on how things get calculated. May not be perfect but should help you along.

APC-MINI-LED-Color-Strategy.bmtp (1.7 KB)

Steve Caldwell
Bome Customer Care

Also available for paid consulting services:

Thanks so much Steve.
I think I see how this math is done. I’ll not get a chance to have a crack at actually applying this to a working project for a few days but will keep you posted.
All this and I’m not entirely sure how I would implement it in a full operational workflow but I do have ideas.


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