edgar-bonet / eRCaGuy_TimerCounter

An Arduino micros()-like function (encapsulated in a library) with 0.5us precision (since the built-in Arduino micros() function has only 4us precision)

THIS LIBRARY IS IN THE PROCESS OF BEING UPGRADED. IT MAY NOT CURRENTLY BE IN A WORKING CONDITION, THOUGH THE ONE AT THE GUMROAD LINK BELOW IS.

Readme for eRCaGuy_TimerCounter

My Gabriel Staples
Readme last updated: 4 Aug. 2015

License: GPLv3 or later (ignore whatever the files say; it is GPLv3)

-I'll correct the license in the files later.

Readme Update History (newest on top)
-20150804 - updated links & formatting
-20140517 - readme written

Click Here to Donate & Download (via Gumroad)

Instructions

Donate and download above. Install the library into the Arduino IDE (using Sketch --> Include Library --> Add .ZIP Library), then run the examples to see how to use the library. You may view the examples in the IDE under File --> Examples --> eRCaGuy_TimerCounter.

Basic Summary

I wrote a libary to get 0.5us precision on a "micros()" replacement function, so that I can get repeatable results reading a PWM or PPM signal, to within 1us. I searched all around the internet and could not find something comparable (or that was easy to use, and maintained the Arduino's ability to write PWM signals via the Servo Libary (which uses the ATmega328's only 16-bit timer/counter, Timer1), so I think this is my first real contribution to the world of Arduino and Radio Control.

Description

• This Timer2_Counter code is a very generic timer tool to be used in Arduino boards in conjunction with, or in replacement of the built-in Arduino micros() function. I decided to write this code because I needed a really precise timer to be able to measure Radio Control pulse width signals using external interrupts and pin change interrupts, and the built-in Arduino micros() function only has 4 microsecond precision, which allows for a lot of variability, or "noise" in the readings. To avoid this variability, while keeping the Atmel 16-bit Timer1 free to continue powering the Servo library, I wrote this code to utilize the 8-bit Timer2. This created a significant challenge, however, in carefully counting timer overflows while ensuring that no overflow count is missed. Through some careful coding I now have it functioning perfectly, counting all overflow interrupts. It works well.
• I'll be adding the ability to use other timers instead of Timer2 next, for more versatility and compatibility with other libraries. This way, you can ensure you're not trying to use the same timer that another library uses.

For more information on this code see here: http://electricrcaircraftguy.com/2014/02/Timer2Counter-more-precise-Arduino-micros-function.html and here: http://www.instructables.com/id/How-to-get-an-Arduino-micros-function-with-05us-pr/

Be sure to check out the links above. I hope you find this useful.
Sincerely,
Gabriel Staples
http://www.ElectricRCAircraftGuy.com