Smooth PWM Output

[vaishnavachath]

I have tried to fix these issues related to PWM,

• spikes occuring while writing zero duty cycle(proposed soln: disabled pwm while writing zero duty/freq)
• smooth pwm output while sweping pwm frequency(proposed soln: suggested implementation alongside current implementation)
• digitalWrite() on ANALOG_OUTPUT(proposed soln: write duty cycle according to value(0/1))

beagleboard#26
beagleboard#30
beagleboard#17

I have uploaded the test video here : https://youtu.be/_CiSsroef18

I couldn't figure out how to write test cases for these patches , that was why i included some non relevant tests,please excuse.

[coveralls]

Coverage increased (+0.06%) to 37.111% when pulling e5b6489 on vaishnav98:master into 61d2fa2 on jadonk:master.

[jadonk]

I want to figure out moving forward how to remove all synchronous reads and writes. For now, I think this is fine because the change will need to be wholesale.

Your video of the tests gives me the confidence to accept this code. Looks fairly clean and readable as well.

Thanks for the great work. This will make a number of people happy.

[vaishnavachath]

Glad to hear that :) , sure I will try to figure out a solution to the issue of removing sync read/write operations in future (didn't do it now for the patch since we need to make consistent changes everywhere).