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4. Software
4.1.
Short Description
The software is written entirely in C. It consists of a collection of standard C library
functions, a preemptive multitasking operating system (CMX) offering basic config-
uration and administration functions (including a command line terminal on a serial
port), and the application software itself, which assures the desired functionality of
the device.
4.2.
Tasks
Following tasks are currently implemented:
The system usually remains in sleep mode. Each 0.5 seconds, an interrupt is gener-
ated by the local 32.76 Khz crystal oscillator. This wakes up the processor and acti-
vates the CMX RTOS, which allows all active tasks to perform their functions. After
all the tasks have finished their jobs, CMX brings the system back to sleep. The 0.5
seconds interrupt routine is also used as time reference for the RTC task.
One of the main concerns of the software design is the power consumption of the
device. The software must ensure that all the peripherals are left in the correct state
in order to reduce their consumption to a minimum; all operations are executed in
the shortest possible time.
• Command Line Interpreter Task
• Radio Task
• Real Time Clock (RTC) Task
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