This node will handle the dashboard switches for lighting and demister. Lighting includes brake light and parking brake lights as well as interior passenger compartment light(s).
NOT included are switches, etc for the HVAC (Heating, Ventilation and Air Conditioning) system. They attach to the node for that side of the dashboard.
Summary of I/O
|Main Light Switch (E1 E20 L9)||30↑ logic high
X power/logic high
58e analog power
31 tied to battery
|58↑ and 56
|Fog Light Switch (E23 K13 L40)||58b Dash illum.
83 power/logic high
|83a and 83b|
|Demister Switch (E15 L39)||58b Dash illum.
+ power/logic high
31 tied to battery
|Brake Light Switches (F F9)||F/1↑ F9/2 logic high||F9/2↑ F/2|
|Brake Warning Light (K7)||None||15 power|
|Dashtop Light Level||Analog power||Analog|
|Dashfront Light Level||Analog power||Analog|
|Dome Light||PWM Power (10W)|
Inputs marked ↑ must remain high, even when the node goes to sleep to conserve the battery. Outputs marked ↑ will cause the node to wake up from sleep mode, in addition to other events.
The node will go to sleep when told to do so by the LINbus master.
The node controller will need one (1) switched output as a logic input for switch sensing and two (3) switched power outputs for driving the indicator lamps as a proxy for the unloading (X) circuit and the same high-side side source can be used to drive the brake warning indicator to proxy ignition (15). A dashboard illumination (58b) proxy is also generated (using PWM) to illuminate switches. The high-side power requirement is small, driving only indicator lamps.
Faults in the devices controlled by the switches can be advised by a slow blinking of the respective switch illumination lamps L9, L39 and L40.
Replacement of the lamps with LEDs would obviate the need to generate a proper supply to drive the existing filament bulbs.
One analog input is required to measure the resistance at the dashboard illumination potentiometer. The other side of the pot is connected to the voltage reference. Seven (7) digital inputs determine switch states.
A small number of I/O isn’t a bad thing. The node’s software remains simple and therefore less prone to undesirable behaviour.