Plip Tester - How to make a remote locking fob tester

If you have a Tip or Trick, some advice or you just want others to know something that is not specific to the fuel a Citroen C3 uses, please, post it here. Manual Gearbox, bodywork, interior, wheels and tyres are all welcome here.
Forum rules
Tips for any Citroen C3

Tips from forum members are encouraged and very welcome.

Questions are not to be posted in this section

No Engine tips

Think: Manual Gearbox, Bodywork, Lighting, Interior, Wheels, Steering, Brakes and Suspension
User avatar
My Name: Arfur Dent

Guru
Posts: 3407
Joined: Sat Jul 23, 2011 3:47 pm
Model: C3 2002-2005, Original shape model
Year: 2002 (52)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 100000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
Has thanked: 305 times
Been thanked: 119 times

Post

When the car doesn't unlock with a press of the button, the remote fob may be faulty, but how do you test it?

The project has 4 main goals;

1. Cheap - it has to be cheap to make as you can buy expensive remote fob testers already.
2. I wanted to get a level of signal to identify a weak performing remote (which has possibly cropped up in the forum previously).
3. I wanted to see the data that is sent from the key, something decodable will prove the fob is in good working order.
4. Software will have to run on the Lexia laptop (Windows XP with USB ports).

The solution costs less than £10 (including antenna) and will decode the key data and show a level of signal on the screen. I uses my lexia laptop and TV Dongle as the receiver. The added benefit is the USB Dongle will also play digital TV and radio programs but that is not covered here ;)

The fob tester consists of my lexia laptop running windows XP, a USB SDR TV Dongle, an aerial and some free software Microsoft .NET framework 3.5, SDR# and RTL-433-WIN32 (Thanks to Megavoid for the windows port of Benjamin Larssons (merbanan on github) rtl-433 software).


How its made :)

Disconnect the Actia/Lexia/Diagbox from the computer.

Buy one of these USB SDR dongle from eBay, which includes an aerial and drivers but DO NOT install the drivers from the CD. Other USB SDRs do work with the software and some don't.
The original SDR USB is difficult to get now, but the compatibility has improved.
I have tested this one and know it works for this job. Connect it to a windows XP laptop (now Diagbox runs on WIn7, so plug it into your windows 7 laptop), the one that runs lexia was Ideal for me. Let windows attempt and probably fail to install its own bulk drivers and do not use the ones on the CD. Attach the aerial to the USB.

USB SDR Dongle for C3 fob tester
USB SDR Dongle for C3 fob tester
This one works, other may not.


The laptop needs Microsoft .NET 3.5 to run SDR Sharp (SDR#) so download .NET 3.5 from microsoft.com and install it if you don't already have it.


Download and install SDR Sharp from sdrsharp.com.

Unzip the sdr-install.zip to a folder of your choice, but remember what your choice was.

In the folder you will find install.bat, run this and allow to install to complete.

You may get a warning from your antivirus about HTTPGET, do not act on this and allow HTTPGET to download the latest version of SD sharp.

Plug in the USB dongle without the supplied CD, use the windows bulk drivers.

Driver install
Driver install
Finish the wizard and ignore any error messages


With SDR# installed and the USB SDR dongle plugged in, run the file zadiag_xp.exe which is found in the newly created sdrsharp folder.

press 'Install Driver' when 'Bulk-in Interface' has been selected in the drop-down list.
(There are some very clear instructions on this step here) if you need them ;)


This will get SDR sharp working, you can test this now if you like by double clicking SDRSharp.exe (Blue square icon) found in the newly created sdr-install folder.

Ensure RTL-SDR / USB is selected in the Source list on the left.

Tune the software to 433.902.000 (433.902MHz) and press the triangle in the top left of the window.

The triangle icon starts the software running and it is then actively monitoring 433.902Mhz for signals. If you press your fob button within range of the aerial the screen will show a blue rise in the graph and the red/orange part will record the signal change as its scrolls. The height of the blue bar in the top screen is directly proportional to the amplitude of the signal (range).

SDR Sharp fob tester for Citroen C3 remote locking
SDR Sharp fob tester for Citroen C3 remote locking



The second part of the project is to detect the bits of data as data and decode them to further prove the remote fob is functioning correctly. To decode the signal I used a program written to decode weather station remote units that operate on 433Mhz, the software only captures part of the rolling code sent to the car from the fob, but you get to see the bits of data and the code rolling on each push. You can find out more about RTL433 here

To get decoding, download a 'not so easy to find' copy of RTL-433_win32 (this one thanks to randall-radf). RTL433 Mirror

Unzip to a folder and remember where you unzipped the files to because you will need to navigate to them later. If you can drop then in the root of C:/ it can save a bit of typing later.

Stop SDR# running when you want to use RTL433 decoding, but leave the USB dongle connected.


To run RTL433, open a command prompt and navigate to the place you unzipped it to (the root of C:/ save much typing)

Copy and paste this line into the command prompt to run RTL433

Code: Select all

rtl_433.exe -f 433902000 -a
my unzipped folder is in the root, so I open a command prompt and paste this:

Code: Select all

C:\rtl_433_win32\rtl_433.exe -f 433902000 -a
which runs RTL 433 and tunes the receiver to 433.903Mhz and waits for a signal (fob button press).

Pressing a fob button while in range of the receiver will prompt RTL443 to decode the signal and display the data in the window.
rtl 433 win 32 output for c3 fob tester
rtl 433 win 32 output for c3 fob tester
Each press of the fob will send data to the program which will then decode it, keep pressing and you should see a screen full like this
Key Fob tester for Citroen C3
Key Fob tester for Citroen C3
You can add an avatar to your account - Avatar or change your vehicle details - Car Bio or even add a signature to your posts - Signature. But this is not all you can do in the User Control Panel :)
User avatar
My Name: Arfur Dent

Guru
Posts: 3407
Joined: Sat Jul 23, 2011 3:47 pm
Model: C3 2002-2005, Original shape model
Year: 2002 (52)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 100000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
Has thanked: 305 times
Been thanked: 119 times

Post

Without tweaking any SDR# filters or gain and using any old unknown fob with an unknown battery, I get a peak shown in the picture below when I press the lock or unlock button. The fob is about 30 to 40 cm from the aerial when testing.
peak amplitude for used fob with unknown battery
peak amplitude for used fob with unknown battery

A video showing with each button press there is a peak on the blue graph centred around 433Mhz in SDR#

Citroen C3 homebrew plip tester
Citroen C3 homebrew plip tester
You can add an avatar to your account - Avatar or change your vehicle details - Car Bio or even add a signature to your posts - Signature. But this is not all you can do in the User Control Panel :)
My Name: Missing Lincs

Moderator
Posts: 844
Joined: Mon Mar 05, 2012 9:29 pm
Model: C3 2002-2005, Original shape model
Year: 2004 (04)
Engine Size: 1.1
Fuel Type: Petrol
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
Location: United Kingdom
Has thanked: 46 times
Been thanked: 35 times

Post

Brilliant solution Arfur. I don't have any problems with remotes at the moment but even so I think I'm going to add this to my 'toolbox'. I already have a spectrum analyser which I've used with a near-field probe to check RF output from keyfobs in the past but the decoding part really appeals.

What I'm thinking is to pre-empt any problems and store data including signal levels from all the remotes in the household so that in the event of problems I have reference data on file.
If at first you don't succeed, destroy all the evidence and pretend you never tried :lol:
User avatar
My Name: Arfur Dent

Guru
Posts: 3407
Joined: Sat Jul 23, 2011 3:47 pm
Model: C3 2002-2005, Original shape model
Year: 2002 (52)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 100000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
Has thanked: 305 times
Been thanked: 119 times

Post

Missing Lincs wrote:Brilliant solution Arfur.
Thanks :D
Missing Lincs wrote:I don't have any problems with remotes at the moment but even so I think I'm going to add this to my 'toolbox'. I already have a spectrum analyser which I've used with a near-field probe to check RF output from keyfobs in the past
Cool toy. It would probably be enough to test if the fob transmits anything or not.
Missing Lincs wrote:but the decoding part really appeals.
Yes, this is the most interesting bit. It still requires some work in the future, for example, I would like to detect the 'battery worn' flag and I am sure there are more than a few numbers and loads of zeros being sent. If you look at what RTL433 can do with the code from various wireless weather station transmitters, I think there is more to be read from the C3 fobs.
Missing Lincs wrote:What I'm thinking is to pre-empt any problems and store data including signal levels from all the remotes in the household so that in the event of problems I have reference data on file.
This is a good idea.

Hopefully the images above will be a good reference point for the C3 fob, but there is an unlimited number of 433Mhz remote controls out there just waiting to give problems.

If you are willing to share screen captures of SDRsharp and data reads from rtl433, feel free to add a topic of non C3 related fob readings. I have a garage door opener to play with and the signal levels may help others with failing fobs of a similar type in the future.
You can add an avatar to your account - Avatar or change your vehicle details - Car Bio or even add a signature to your posts - Signature. But this is not all you can do in the User Control Panel :)
My Name: Missing Lincs

Moderator
Posts: 844
Joined: Mon Mar 05, 2012 9:29 pm
Model: C3 2002-2005, Original shape model
Year: 2004 (04)
Engine Size: 1.1
Fuel Type: Petrol
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: TU3 (75 PS)
Location: United Kingdom
Has thanked: 46 times
Been thanked: 35 times

Post

If anyone does gather 'reference' data, it might be helpful to use a basic test configuration. For instance, aerial to remote distance, eg 1m. Orientation of remote transmitter, eg upright, back to receiving aerial and on a level plane - this can mean aerial and remote stood on the same table, 1m apart ;) )

Thinking about signal levels, each test system will have differences, so absolute comparison won't be on the cards but it should be possible to get some typical figures for reference if someone's having problems.
If at first you don't succeed, destroy all the evidence and pretend you never tried :lol:
  • Similar Topics
    Replies
    Views
    Last post