Design a wind direction measurement instrument using the 8-bit ADC. You are given a transducer with a resistance that is linearly related to the wind direction. As the wind direction varies from 0 to 360 degrees, the transducer resistance varies from 0 to 1000 Ω. The frequencies of interest are 0 to 0.5 Hz, and the sampling rate will be 1 Hz. (See Exercise 6.5.)
a) Show the analog interface between the transducer and the ADC port channel 7. Only the +5 V supply can be used. Show how the analog components are powered. Give chip numbers, but not pin numbers. Specify the type and tolerance of resistors and capacitors.
b) Write the ritual and gadfly function/subroutine that measures the wind direction and returns a 16-bit unsigned result with units of degrees. That is, the value varies from 0 to 359. (You do not have to write software that samples at 1 Hz, simply a function that measures wind direction once.)
Exercise 6.5
Design a wind direction measurement instrument using the input capture technique. Again, you are given a transducer that has a resistance that is linearly related to the wind direction. As the wind direction varies from 0 to 360 degrees, the transducer resistance varies from 0 to 1000. The frequencies of interest are 0 to 0.5 Hz, and the sampling rate will be 1 Hz. One way to interface the transducer to the computer is to use an astable multivibrator like the 555. The period of a 555 timer is 0.693⋅CT⋅(RA+2RB). The 555 output could be connected to the Input Capture Port Channel 7.
a) Show the hardware interface.
b) Write the ritual and gadfly function/subroutine that measures the wind direction and returns a 16-bit unsigned result with units of degrees (i.e., the value varies from 0 to 359). (You do not have to write software that samples at 1 Hz, simply a function that measures wind direction once.)