This is a reference design for a Local Interconnect Network (LIN) enabled, steering wheel keypad module with light emitting diode (LED) backlighting. The design is based on the MC68HC908QY4 microcontroller and MC33689 LIN system basis chip (SBC). The system consists of the keypad module, which is a slave on a LIN network, a satellite board which contains more buttons and backlighting LEDs for the right side of the steering wheel, and a LIN master node (emulated).
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Features
- Monitoring of 13 buttons for cruise control, HVAC, and radio controls on an automotive steering wheel
- LIN connectivity using LIN 1.3 standard messaging
- Low-cost 16 pin MC68HC908QY4 microcontroller
- Autobauding to any LIN bus speed from 1-20kbps
- LED backlighting with 16 network controlled brightness levels using PWM
- 3 wire connection to clock-spring, independent of button count (LIN, Vbatt, ground)
- LIN communications and PWM backlighting achieved using single timer module
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