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Exercise 11.3 CPU selection
Given the following application, describe the desired functionalities of a microprocessor, in terms of peripheral modules and CPU speed, for automobile heating, ventilation and air conditioning control.
The automatic HVAC controller should have
a fan with 5 fan speeds that can be turned on and off (5 ouput port bits)
an air compressor that can be turned on/off (another output bit)
3 temperature sensors (3 A/D inputs or one multiplexed A/D input)
- ambient, engine coolant, and engine compartment temperatures
an spi serial port to connect to the display penal
a CAN communication channel for communication to the main vehicle controller
Obviously we want to use a microcontroller – not a DSP or GPP chip. Temperature and display panel are slow so the CAN communication port determines the required CPU speed.