May 012014

Since I wrote the posts on 'Home Automation RF Protocols for simple devices' back in 2012, I have received some questions and feedback, which I find very enjoyable. Unfortunately I have had to turn off the comment options, as I have also received a lot of spam. Still people who really want to, have managed to find my email address (in the 'About Me' page). Some of the questions was on devices which I haven't made the decoding of myself. This made me quite curious, so I went and bought some of these devices.

Now I have three different makers of simple devices, namely Proove from 'Kjell & Company', Anslut from 'Jula', and Nexa which is a wellknown brand not belonging to a special franchise but can be found almost anywhere.

Starting with the 'Anslut' devices, it is really similar to the Proove one when just looking at them. Here is a picture of the transmitters, with Proove to the left and Anslut to the right.



Opening the Anslut transmitter the PCB is also identical to Proove, but checking the IC, it was not the same as in my Proove transmitter.
This one was labeled,
But after some searching on the internet it seems to be made by Holtek too.
I would imagine it is just another version of their '8-Bit OTP MCU with RF Transmitter' line-up of IC:s.
The Xtal is marked 13.560 MHz, which is 1/32nd of 433.92 MHz.

The pin-out of the IC is identical to the one on the Proove device

 Vcc  9-|       |-8 Vcc
     10-|       |-7
     11-|       |-6
 Vcc 12-|       |-5 SW4
 SW8 13-|       |-4 SW3
 SW7 14-|       |-3 SW2
 SW6 15-|       |-2 SW1
 SW5 16-|      o|-1 Dout

As everything is so similar between these devices, I strongly suspect the decoded data to also be very similar.
This time around I have a digital logic analyzer to decode the data transmitted on the Dout pin.

To my surprise I see a packet burst consisting of SIX packets, and not four as I saw last time. Of course this is most likely due to measurement tool limitations, as I used a USB oscilloscope last time, and it might not have had the bandwidth/capacity to capture all of the data. Anyway, this is what it looks like with the logic analyzer.



Zooming in a bit on the packet burst.


Zooming in on one packet to decode bits.


Defining the pulses.
High 250 us, low about 2750 us  -> Sync
High 250 us, low about 1500 us. -> Zero (0)
High 250 us, low 250 us. -> One (1)
Last bit.
High 250 us, low 10500 us. -> Pause
A packet consist of, Sync + Data + Pause.

Decoding 'Data part' of a packet.

0        10        20        30        40        50           60
1234567890123456789012345678901234567890123456789012 34 56 7890 1234

Bits #01-52 -> TxCode (T)
Bits #53-54 -> Group (G)
Bits #55-56 -> On/Off (O)
Bits #57-60 -> ? Dimming/Channel ? (D)
Bits #61-64 -> Device Nbr (N)

As every other bit sent over the air is redundant, it is the inverse of the previous bit, the packet consist of 32 logical bits

Going back to my Proove tranmitter, and hooking it up to the digital logic analyzer, it also shows a packet burst consisting of six packets. All of the decoding is the same as for the Anslut device.
Defining the pulses.
High 250 us, low about 2500 us  -> Sync
High 250 us, low about 1250 us. -> Zero (0)
High 250 us, low 250 us. -> One (1)
High 250 us, low 10000 us. -> Pause

Time to check the Nexa device. Note this is the simple version, and cheap, of their devices.

First I open up the transmitter, and can immediately see that it is completely different to the other ones.


This is how the other side of the pcb looks like.


The component on the frontside marked 'H R4334' at position SAW101, is a SAW filter with three pins.
1 - Input
2 - Output
3 - GND

Debuging the IC, which has no markings on it, on the backside gives.

 5 -|        |- 4 
 6 -|        |- 3 
 7 -|        |- 2 
 8 -|       o|- 1

Using the oscilloscope to have a look at the signals.	 
1 - 3.8 V
2 - Dout, Pulse train when pressing button
3 - 
4 - 3.8 V noisy
5 - < 1 V rippled
6 - same as 5
7 - same as 5
8 - GND

So, we seem to have a Dout pin here too. Time to hook up that analyzer again.

This is what a packet burst looks like. Note, only five packets in the burst.

Zooming in a bit on that burst.


Finally here is how a packet looks like.


Data part time decoded:
High 250 us, low 2750 us -> Sync
High 250 us, low 250 us -> one
High 250 us, low 1250 us -> zero
High 250 us, low 10000 us -> Pause

This is exactly the same as the Proove device timing, and as expected the data part of the packet is also the same as the Anslut and Proove devices.

With this new knowledge, I have decided to update/change my 'Home Automation, RF Protocols' page to reflect my new findings, and to only have device data which I have decoded myself.

I have also updated the Arduino library that I made some years ago. Since there are some differencies between Proove/Anslut and Nexa, such as the channel code and the way to number unit 1 to 3, I made two librabries: Proove/Anslut and Nexa.

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