BMW S1000R Accessory Light Flasher – First Prototype

I built this about a year ago.  I prototyped a circuit that used an ATTiny85 microcontroller to drive a p-channel (high side) mosfet.  The idea was to use the microcontroller to strobe the Clearwater Darla LED accessory lights.

The circuit worked as expected, but that click-click-click-click noise is bad. I thought the functionality of the led “instant-on” was via a 12v signal to the dc-dc circuit in the led light, but it is actually a mechanical relay. Strobing anything mechanical is no bueno.

I  completely changed my strategy after this test.  A little experimenting and I discovered that the accessory lights are controlled by a PWM signal which controls the light intensity (low to full power).

Rigol Oscilloscope i2c Bus Decoding

I built a weather station last year. Even though I sprayed a conformal coating on the PCB to help it resist humidity exposure, the temp/humidity/barometric pressure sensor flaked out from exposure to the elements.  While fixing it, I decided to “geek out” a bit and hook the oscilloscope up to decode the i2c bus messages.  My notes for reference.

High Level:

  1. Connect probes, make sure they are setup correctly (10:1, etc.). Then set vertical scale and time-base.
  2. Set the triggering conditions to match the signal encoding
  3. Set the decode conditions to match the signal encoding
  4. Optional – use the event table to capture and export the data

Channel 1 probe to SCL (Clock)
Channel 2 probe to SDA (Data)

Scope Config
Set to 2v/div, 100us
Trigger – i2c, SCL->Channel 1, SDA->Channel 2, When->Start, Sweep->Auto
Decode – i2c, BusStatus->On, SCLK->Channel 1, SDA->Channel 2, SCL Threshold->1.80v, SDAThreshold->1.80v, Format->Hex (whatever is appropriate)

Enable the event table if you want to capture data which allows you to also export the data to a usb drive.