Replacing the stock BMW R1100RT radio & remote controls with a Pioneer head unit – Part 1

Testing BMW remote on Pioneer radio

Due to a change in French law, people will no longer be allowed to drive – or ride – with headphones or in-ear hands free or navigation kit as from July 1st 2015. As my BMW R1100RT was pre-equipped with a radio and speakers, but the old Clarion radio was shot, I decided to reinstall a radio, and have some fun reconnecting the OEM remote radio controls with a Pioneer MVH-X370BT head unit.

This head unit is a half-length digital radio (no cassette, no CD), AM/FM radio, MP3 support, aux input support, bluetooth with hands free phone with an external wired microphone, with 4×50 watt output plus RCA connectors to go to an optional amplifier.

This unit also supports a wired remote control, that after a short internet search, is a very simple, 3 wire, 3.5 millimetre jack plug that executes radio functions according to a resistor array. This is  normally supplied in an adapter box, that is sold for 80 or so euros in car centres, that interfaces between OEM steering wheel remote controls, and the wired remote plug on the back of the radio.

After a quick internet search, this little adapter box contains no smart electronics, it just contains a basic set of resistors that are connected to the wheel functions, and from there, the head unit detects the resistance on the line and executes the corresponding radio function.

The BMW R1100RT default remote controls only have 5 functions : Operating LED, Channel up, channel down, volume up and volume down. For any other functions, you have to grope around in the glovebox by hand on the radio console.

OEM Wired Remote male plug pin out

OEM wired remote male connector pinout

OEM Wired Remote male plug pin out

On the radio end of the remote control, you have an 8 pin DIN plug that plugged into the back of the stock unit. This will have to be taken apart, trace what button commands what wire, then check that on this head unit, the resistance values needed for the functionnality that we will add back.

I have not reconnected the LED on the remote control, but I want to reactivate the 4 controls, and if possible, add 2 extra: “Mute” and “Change Source/Turn off”, but these will be on a seperate switch.

The OEM plug is pinned out as follows:

Pin Function Wire colour
1 Common main signal wire Orange
2 Channel up Red
3 Unused Not connected (no wire)
4 Channel down Green
5 Unused Yellow
6 Unused Grey
7 Volume up Purple
8 Volume down Blue

These wires will be connected to a small project box, through a series of resistors for each function, that will feed back into the radio.

To identify what value resistors are needed for the project, a some starting values for people who wanted to hack their Pioneer head unit remote without paying a fortune for a commercial adapter, but before blindly following the values, I wanted to test them on my head unit with a variable resistor test rig, but first I needed to wire up the radio to the current radio and ignition wires.

Connecting the radio

R1100RT radio power wiring

R1100RT radio power wiring

Connecting the radio was not too difficult, though you have to cut out some wires and splice the back of the ISO plugs into the existing cabling.

The Pioneer radio needs always-on mains power for memory when off, and it also will use this power for general use as the line is a direct power line from the battery through the F3 fuse (red and white wire).

The head unit also uses the ignition switch as an activation signal to switch from standby (and displaying the time on the interface) , to activating all radio functions (purple and white wire), and the brown wire is connected to ground.

These wires need to be spliced to the power part of the ISO connectors on the back of the radio (check the manual for the correct colours)

For the audio part, the blue and blue-black wire will be spliced to the wires for the right hand speaker, and the yellow and yellow-black to the wires for the left hand speaker.

If you are feeling adventurous, you could wire the rear left/right connectors to in-helmet speakers and then play with the front-rear balance to avoid blowing your ears out with 50 watts of sound… Maybe not recommended but it has been mentionned in other BMW forums!

Connect the antenna to the back of the radio, and then turn on and make sure you have sound! Once you can confirm that the radio works, you can then start checking the resistor values needed to rewire the wired remote, with a variable resistor test rig and a multimeter.

Resistor value to remote radio function test rig

Variable resistor test circuit

Variable resistor test circuit

I made up a test rig with the following:

  • A prototyping bread board
  • 1 x 100kΩ potentiometer  (variable resistor)
  • A big Lego wheel,
  • A digital multimeter with 200 to 200 000 ohm range
  • One male-male 3.5 mm standard stereo jack (3 connectors on the male plug, called “Tip-Ring-Sleeve” or TRS)
  • One corresponding 3.5 mm “TRS” female socket
  • A microswitch.
  • Assorted wiring

Fit and stick the big Lego wheel on the shaft of the potentiometer ( as it’s easier to fine tune to within a couple of ohms with a 10cm dial than with the 5 mm shaft ) set up power input into left and centre connectors of the pot, send the output to the microswitch, and wire the input to both the tip of the jack to the radio wired remote jack, and the output of the microswitch to both the negative multimeter and the ring of the wired remote jack.

From there, and a known set of Pioneer values to start from, I set the potentiometer to each value that was needed, then checked it against the radio.

The “known” values were taken from the JVDE blog ( http://jvde.net/node/7 ) , who I thank for publishing the base values and extra information and who gave me the idea to build a test rig to double check the values first.

I disconnected the wired control plug from the radio and turned it off before connecting the multimeter to set and check resistance values, and then disconnected the multimeter from the circuit before reconnecting and turning the radio back on to check what the value actually did.

This way, you avoid cross talk between the multimeter and the radio. Adding a microswitch (an leftover in my parts bin) allowed an easier value test on the radio rather than the quicker and uglier way of touching 2 pieces of wire together!

This radio has the following remote functions that will be hooked up, with the corresponding confirmed resistor values:

Operation Resistance in ohms
Short press: Frequency up / next track. Long press: Frequency scan up / fast forward 8.2kΩ
Short press: Frequency down / previous track. Long press: Frequency scan down / rewind 12kΩ
Volume up 15kΩ
Volume down 22kΩ
Short press: Change source. Long press: Turn off 1.2kΩ
Mute 3.3kΩ

Once the basic values I wanted from the remote features were confirmed with my head unit, time to start soldering the interface.

Building the interface

Remote control resistor array circuit

Remote control resistor array circuit

There is nothing complex here, everything is plain and simple passive components, added to a small project box. Using some sealant to keep moisture out of the box around the wire holes, it could be mounted onto the outside of the glovebox, but given that the radio is half hight, it would not be a problem to fix to the bottom of the box….

  • 1 small waterproof project box
  • 6 resistors, one for each needed value
  • 1 prototyping copper striped pre-drilled bakerlite project board
  • 1 female stereo 3.5 mm jack plug (TRS – ideally a chassis mounted socket to attach to the side of the box)
  • 1 male-male 3.5 mm jack stereo cable
  • Assorted wiring
  • RTV silicone to seal the project box (but hot glue would work just as well)

Using some imagination, it could even be possible to fit the radio under the space at the rear of the bike behind the passenger saddle if you could add on/off, mute, and a few other functions to the remote controls to free up space in the glovebox.

Finished resistor array

Finished resistor array

The main annoyance about glovebox mounting is that I also use the glovebox when driving long distances to keep a bottle of water, a litre of engine oil and my GPS when parked for a pitstop at roadside services… Maybe I need to add a secure tank bag…

 

 

 

 

 

 

Part 2 will deal with connecting the remote control interface to the radio, and installing the radio on the bike.

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