AN2264

Freescale Semiconductor, Inc. Application Note AN2264/D Rev. 0, 3/2002 LIN Node Temperature Display by Freescale Semiconductor, Inc... Peter Topping 8/16 Bit Applications Engineering Motorola, East Kilbride Introduction Many of the problems of excessive wiring within a car can be resolved by using a serial multiplex bus like CAN or LIN. The LIN (Local Interconnect Network, reference 1) bus is lower in cost and ideally suited to use within a door or in other areas in the car where its limited data rate of 20,000 baud is adequate. The display of external temperature is an application which falls into this category. As a common location for the outside temperature sensor is in a wing mirror, the data often originates from the door. The actual display is, however, within the car some distance away and the LIN bus is eminently suitable to facilitate the connection. A LIN node requires only 3 wires; there is one LIN data line, the other two connections being the positive and negative supplies. This application note presents the design of a temperature display LIN slave node. It was developed as part of a complete door project which also included the keypad module described in application note AN2205. The messaging scheme for the door incorporated a byte for temperature in the mirror response field as shown in table 1. The LIN master is, in this case, the body controller. On a regular basis, say every 100ms, the master sends a frame header with the mirror’s ID and it responds wi...