Added routines for SPI communication.
Added initialization of ADS1248 ADC that is used for Pt1000 measurements.
Added a start conversion function for the ADS1248 ADCs and set the data direction of the start and ready signal pins in the init function.
Added a function to read the ADC result data from the ADC1248.
Added interrupt handling of the ready signal from the ADS1248 ADCs, however the ADC data is not yet read after the interrupt.
Added code for the use of the 7-segment display driver chip MAX7221 to
display temperature and humidity.
Added the display of the temperature and humidity as a scheduled task.
Added distinction of clock phases in SPI protocol for different chips.
Using the Makefile to define the CPU frequency that is passed to GCC.
Integrated the measurement of the temperature with the ADS1248 ADC into
the process. Made the interface such that the two ADS1248 chips appear
as one.