I have a nice Alfa 147 instrument cluster, which comes with an 18pin connector.
According to the wiring diagram on AutoData.com the pins are as below, and unlike the simpler models the 147 uses a serial differential VAN-H/VAN-L pair of wires to send all data.
The problem I now have is the VAN BUS Protocol ( not CAN BUS but VAN BUS - Vehicle Area Network ), its not well documented and tends to be per-manufacturer. I would like to reuse this very beautiful instrument cluster in my full sim dash but without the car (ECU and Multipurposes IO cabling rig and sensor inputs ) to go with it I cant work out what the protocols are.
Anyone have a dash they have in parts that can hook up some oscilloscope, or VAN BUS monitor to find out what the protocol is? ( I am happy to help with the decoding part )
Pinout for Alfa 147 according AutoData:
Pin 6 - Lights +v12 - "Headlamp low beam relay" ( Switched 12V )
Pin 5 - Lights GND or Headlight Adj Motor?
Pin 10 - Feed from "Engine control module (ECM)"
Pin 15 - Driver Seatbelt -V/GND
Pin 1 - +v 12 ( according to socket pinout picture ) - ( Unswitched 12V )
Pin 2 - +v 12 ( according to socket pinout picture ) - ( Switched 12V )
Pin 3 - Feed from "Multifunction control module" ( VAN Bus )
Pin 4 - Feed from Multifunction control module" ( VAN Bus )
Pin 7 - GND or -V
Pin 11 - Feed from "Headlamp adjustment switch" ( Trip computer control switch assembly ) - Probably analogue levels
Pin 9 - Feed from "Headlamp adjustment switch" ( Trip computer control switch assembly ) - Probably analogue levels
Pin 16 - Feed from "Headlamp adjustment switch" ( Trip computer control switch assembly ) - Probably analogue levels
Pin 14 - Feed from "Supplementary restraint system (SRS) control module"
Pin 13 - Feed from "Supplementary restraint system (SRS) control module"
Pin 12 - Feed from "Inertia fuel shut-off (IFS) switch" from GND/-V
( From my post on the Simulation Forum: Alfa Romeo 147 Cluster Pin's
Also information on VAN bus:
VAN Bus Interfacing
"VAN uses a differential bus to remove the effect of common mode noise, the electrical signals are the same as CAN. .... VAN nodes all have their own clocks hence have to perform some level of clock recovery ... Manchester coding is a popular solution to this problem ... VAN data is broadcast on the bus in discreete frames of data encoded using E-Manchester that include an Identifier to allow recievers to filter the data they are interested in. Frame marking is made through the use of E-Manchester violations
This coding of every 4 bits by 5 bits makes length information a little ambiguous unless you remark on the codin (CAN is even more of a pain through the use of data dependant bitstuffing to enable clock recovery). For this reason I like to refer to Time Slices at this level, a Time Slice (TS) is the time taken to transmit a dominant or recessive bit on the bus in real time. Hence 4 bits take 5TS to transmit due to the E-Manchester bit being appended. A 125kbps VAN bus results in 1TS=8uS.
Circuit for monitoring your VAN bus
VAN Bus Interfacing