A very cheap RGB LED controller

LED strips are nice, I like them a lot. Especially the (warm) white ones. We use them in the kitchen and behind the TV; in both cases as a replacement for light bulbs and/or fluorescent tubes. Looks very nice.

So when I could get my hands on some cheap white LED-strip, I didn’t hesitate and bought 10 meters. Those LED strips (which haven’t even arrived yet) come with a 12V adapter and a small ‘box’ with IR receiver and a small credit-card sized IR remote. That’s OK for RGB LED strips in the child bedrooms, but not when those LED strips are going to be used in the living room, entrance or anywhere else. So I needed a simple LED controller; not too expensive, and that has just the stuff I need – the controller and a way to send commands to control the strips individually. And last week I found the Conrad MS-35 RGB LED controller: cheap and no unneeded accessories. If you want you can even add buttons to the controller or an IR receiver (both connected to the controller by means of the headers on the PCB) but I don’t need all that – just this small controller for 15 euro, that’s all I need. Cheap and the user reviews weren’t bad either, so why not try it.

I added the P522J USB programming cable to the shopping basket and today those goodies arrived.

Time for some good-old serial port sniffing… The USB programming cable uses the Silicon Labs CP210x USB to UART Bridge driver (which is on the mini driver CD that comes with the cable). Now let’s see what happens when I try to program a so-called user sequence with the software that came with the controller:

User sequence programming

First only the red channel goes on, next only green and after that blue. And I added some variations to the time values, so it’s easier to find them back in the communication between the software and the controller. The software has a ‘Send program’ button for that so after I started a Serial port sniffer, I clicked that button and had a look at what was sent to the controller:

> 02 03 00 00 00 00 00 f3 23
< 61
> 03 00 ff 00 00 04 01 14 e4
< 61
> 03 01 00 ff 00 05 02 54 80
< 61
> 03 02 00 00 ff 06 03 73 41
< 61
> 0a 01 08 00 00 00 00 10 4a
< 61

OK; 61 must be the ACK.  The 02 on line 1 must be some ‘start programming’ id, the 03 is the number of colour transitions. Line 3 contains the first transition, line 5 the 2nd transition and line 7 the 3rd transition. And it’s obvious that the transition line contains a sequence id (pos 2), the R value (ff), G value (00), B value (00), cross-fade time (04) and the hold-time (01). And the last 2 bytes are the CRC16. Byte value 0a on line 9 must be some end programming id, followed by the User sequence id (01) ?? Don’t know what the 08 on line 9 is for…

Edit color dialog

Although this is nice, all I really need is a very simple command to set the R,G and B values – nothing more.

Lets see what more the MS-35 software has to offer.

There’s an Edit button in the User-sequence programming dialog; let’s see what happens there.. hey that’s a WYSIWYS (what you set is what you see) dialog with 3 sliders and some buttons to quickly select some colors. I changed 1 of the sliders and immediately the LED strip responded..

Let’s fire up the sniffer once more! With every change of either the R-, G- or B- value I saw the sniffer capturing a packet, so that should contain what I was looking for:

> 01 00 f6 6d 92 00 00 94 65
< 61
> 01 00 f6 6e 92 00 00 d0 65
< 61

Here, the G value was changed from 109 (decimal) to 110.


Done, I know what I need to know! 🙂

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4 Responses to A very cheap RGB LED controller

  1. J.J. Bakker says:

    Are this ledstrips from Quintezz?

  2. Pingback: Conrad MS-35 LED controller revisited - Digits Domotica Blog

  3. Pingback: Down from 4 to … - Digits Domotica Blog

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