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Updated to version 0.2.1, for Win *and* Linux
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‎GS_timing.py

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"""
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timing.py
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-create some low-level Arduino-like millis() (milliseconds) and micros()
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(microseconds) timing functions for Python
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By Gabriel Staples
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http://www.ElectricRCAircraftGuy.com
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-click "Contact me" at the top of my website to find my email address
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Started: 11 July 2016
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Updated: 7 Sept 2016
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History (newest on top):
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* 20160907 - v0.2.1 created - updated delay functions to use modulus operator to guarantee proper C uint32_t-like underflow subtraction behavior when the timer rolls over
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* 20160813 - v0.2.0 created - added Linux capability
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* 20160711 - v0.1.0 created - functions for Windows *only* (via the QPC timer)
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References:
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WINDOWS:
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-personal (C++ code): GS_PCArduino.h
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1) Acquiring high-resolution time stamps (Windows)
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-https://msdn.microsoft.com/en-us/library/windows/desktop/dn553408(v=vs.85).aspx
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2) QueryPerformanceCounter function (Windows)
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-https://msdn.microsoft.com/en-us/library/windows/desktop/ms644904(v=vs.85).aspx
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3) QueryPerformanceFrequency function (Windows)
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-https://msdn.microsoft.com/en-us/library/windows/desktop/ms644905(v=vs.85).aspx
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4) LARGE_INTEGER union (Windows)
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-https://msdn.microsoft.com/en-us/library/windows/desktop/aa383713(v=vs.85).aspx
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-*****http://stackoverflow.com/questions/4430227/python-on-win32-how-to-get-
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absolute-timing-cpu-cycle-count
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LINUX:
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-http://stackoverflow.com/questions/1205722/how-do-i-get-monotonic-time-durations-in-python
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PYTHON (general):
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-https://docs.python.org/3.5/library/ctypes.html - ctypes referene page
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"""
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import ctypes, os
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#Constants:
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VERSION = '0.2.1'
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#-------------------------------------------------------------------
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#MODULE FUNCTIONS:
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#-------------------------------------------------------------------
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#OS-specific low-level timing functions:
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if (os.name=='nt'): #for Windows:
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def micros():
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"return a timestamp in microseconds (us)"
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tics = ctypes.c_int64() #use *signed* 64-bit variables; see the "QuadPart" variable here: https://msdn.microsoft.com/en-us/library/windows/desktop/aa383713(v=vs.85).aspx
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freq = ctypes.c_int64()
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#get ticks on the internal ~2MHz QPC clock
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ctypes.windll.Kernel32.QueryPerformanceCounter(ctypes.byref(tics))
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#get the actual freq. of the internal ~2MHz QPC clock
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ctypes.windll.Kernel32.QueryPerformanceFrequency(ctypes.byref(freq))
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t_us = tics.value*1e6/freq.value
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return t_us
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def millis():
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"return a timestamp in milliseconds (ms)"
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tics = ctypes.c_int64() #use *signed* 64-bit variables; see the "QuadPart" variable here: https://msdn.microsoft.com/en-us/library/windows/desktop/aa383713(v=vs.85).aspx
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freq = ctypes.c_int64()
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#get ticks on the internal ~2MHz QPC clock
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ctypes.windll.Kernel32.QueryPerformanceCounter(ctypes.byref(tics))
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#get the actual freq. of the internal ~2MHz QPC clock
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ctypes.windll.Kernel32.QueryPerformanceFrequency(ctypes.byref(freq))
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t_ms = tics.value*1e3/freq.value
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return t_ms
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elif (os.name=='posix'): #for Linux:
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#Constants:
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CLOCK_MONOTONIC_RAW = 4 # see <linux/time.h> here: https://github.com/torvalds/linux/blob/master/include/uapi/linux/time.h
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#prepare ctype timespec structure of {long, long}
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#-NB: use c_long (generally signed 32-bit) variables within the timespec C struct, per the definition here: https://github.com/torvalds/linux/blob/master/include/uapi/linux/time.h
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class timespec(ctypes.Structure):
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_fields_ =\
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[
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('tv_sec', ctypes.c_long),
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('tv_nsec', ctypes.c_long)
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]
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#Configure Python access to the clock_gettime C library, via ctypes:
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#Documentation:
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#-ctypes.CDLL: https://docs.python.org/3.2/library/ctypes.html
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#-librt.so.1 with clock_gettime: https://docs.oracle.com/cd/E36784_01/html/E36873/librt-3lib.html #-
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#-Linux clock_gettime(): http://linux.die.net/man/3/clock_gettime
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librt = ctypes.CDLL('librt.so.1', use_errno=True)
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clock_gettime = librt.clock_gettime
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#specify input arguments and types to the C clock_gettime() function
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# (int clock_ID, timespec* t)
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clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
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def monotonic_time():
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"return a timestamp in seconds (sec)"
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t = timespec()
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#(Note that clock_gettime() returns 0 for success, or -1 for failure, in
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# which case errno is set appropriately)
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#-see here: http://linux.die.net/man/3/clock_gettime
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if clock_gettime(CLOCK_MONOTONIC_RAW , ctypes.pointer(t)) != 0:
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#if clock_gettime() returns an error
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errno_ = ctypes.get_errno()
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raise OSError(errno_, os.strerror(errno_))
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return t.tv_sec + t.tv_nsec*1e-9 #sec
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def micros():
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"return a timestamp in microseconds (us)"
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return monotonic_time()*1e6 #us
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def millis():
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"return a timestamp in milliseconds (ms)"
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return monotonic_time()*1e3 #ms
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#Private module function
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#-see here for use of underscore to make "module private": http://stackoverflow.com/questions/1547145/defining-private-module-functions-in-python/1547160#1547160
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#-see here for example of constrain function: http://stackoverflow.com/questions/34837677/a-pythonic-way-to-write-a-constrain-function/34837691
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def _constrain(val, min_val, max_val):
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"constrain a number to be >= min_val and <= max_val"
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if (val < min_val):
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val = min_val
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elif (val > max_val):
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val = max_val
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return val
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#Other timing functions:
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def delay(delay_ms):
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"delay for delay_ms milliseconds (ms)"
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#constrain the commanded delay time to be within valid C type uint32_t limits
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delay_ms = _constrain(delay_ms, 0, (1<<32)-1)
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t_start = millis()
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while ((millis() - t_start)%(1<<32) < delay_ms): #use modulus to force C uint32_t-like underflow behavior
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pass #do nothing
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return
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def delayMicroseconds(delay_us):
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"delay for delay_us microseconds (us)"
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#constrain the commanded delay time to be within valid C type uint32_t limits
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delay_us = _constrain(delay_us, 0, (1<<32)-1)
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t_start = micros()
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while ((micros() - t_start)%(1<<32) < delay_us): #use modulus to force C uint32_t-like underflow behavior
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pass #do nothing
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return
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#-------------------------------------------------------------------
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#EXAMPLES:
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#-------------------------------------------------------------------
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#Only executute this block of code if running this module directly,
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#*not* if importing it
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#-see here: http://effbot.org/pyfaq/tutor-what-is-if-name-main-for.htm
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if __name__ == "__main__": #if running this module as a stand-alone program
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#print loop execution time 100 times, using micros()
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tStart = micros() #us
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for x in range(0, 100):
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tNow = micros() #us
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dt = tNow - tStart #us; delta time
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tStart = tNow #us; update
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print("dt(us) = " + str(dt))
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#print loop execution time 100 times, using millis()
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print("\n")
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tStart = millis() #ms
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for x in range(0, 100):
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tNow = millis() #ms
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dt = tNow - tStart #ms; delta time
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tStart = tNow #ms; update
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print("dt(ms) = " + str(dt))
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#print a counter once per second, for 5 seconds, using delay
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print("\nstart")
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for i in range(1,6):
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delay(1000)
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print(i)
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#print a counter once per second, for 5 seconds, using delayMicroseconds
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print("\nstart")
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for i in range(1,6):
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delayMicroseconds(1000000)
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print(i)
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‎LICENSE renamed to ‎LICENSE.txt

File renamed without changes.

‎README.md

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# PyTiming
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## Description:
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Create some low-level Arduino-like millis() &amp; delay() (for milliseconds) and micros() and delayMicroseconds() (for microseconds) timing functions for Python
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Create some low-level Arduino-like millis() & delay() (for milliseconds) and micros() and delayMicroseconds() (for microseconds) timing functions for Python.
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Compatible with Python in both Windows *and* Linux. Has ultra-great resolution timestamps (sub-microsecond), even in older versions of Python 3 which don't natively support (in the [time](https://docs.python.org/2.7/library/time.html) module, for instance) high resolutions like this.
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## Website:
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http://www.electricrcaircraftguy.com/2016/07/arduino-like-millisecond-and-microsecond-timestamps-in-python.html
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## Comments:
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* 22 July 2016: This module works for Python in Windows only so far. If anyone would like to expand it to support Linux too, please do.
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Thanks,
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## History:
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(newest on top)
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* 20160907 - v0.2.1 created - updated delay functions to use modulus operator to guarantee proper C uint32_t-like underflow subtraction behavior when the timer rolls over
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* 20160813 - v0.2.0 created - added Linux capability
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* 20160711 - v0.1.0 created - functions for Windows *only* (via the QPC timer)
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## Author:
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Gabriel Staples
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www.ElectricRCAircraftGuy.com
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www.ElectricRCAircraftGuy.com
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-click "Contact me" at the top of my website to find my email address

‎sleep_test.py

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"""
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sleep_test.py
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-see what the resolution of the time.sleep() function is
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By Gabriel Staples
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http://www.ElectricRCAircraftGuy.com
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-click "Contact me" at the top of my website to find my email address
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13 Aug. 2016
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"""
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import time
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import GS_timing as timing
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def delayMicroseconds(n):
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time.sleep(n / 1000000.)
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def delayMillisecond(n):
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time.sleep(n / 1000.)
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t_start = 0
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t_end = 0
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#using time.sleep
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print('using time.sleep')
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print('delayMicroseconds(1)')
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for x in range(10):
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t_start = timing.micros() #us
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delayMicroseconds(1)
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t_end = timing.micros() #us
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print('dt (us) = ' + str(t_end - t_start))
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print('delayMicroseconds(2000)')
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for x in range(10):
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t_start = timing.micros() #us
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delayMicroseconds(2000)
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t_end = timing.micros() #us
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print('dt (us) = ' + str(t_end - t_start))
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#using GS_timing
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print('\nusing GS_timing')
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print('timing.delayMicroseconds(1)')
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for x in range(10):
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t_start = timing.micros() #us
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timing.delayMicroseconds(1)
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t_end = timing.micros() #us
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print('dt (us) = ' + str(t_end - t_start))
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print('timing.delayMicroseconds(2000)')
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for x in range(10):
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t_start = timing.micros() #us
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timing.delayMicroseconds(2000)
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t_end = timing.micros() #us
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print('dt (us) = ' + str(t_end - t_start))
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"""
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SAMPLE RESULTS ON MY WINDOWS 8.1 MACHINE:
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using time.sleep
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delayMicroseconds(1)
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dt (us) = 2872.059814453125
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dt (us) = 886.3939208984375
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dt (us) = 770.4649658203125
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dt (us) = 1138.7698974609375
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dt (us) = 1426.027099609375
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dt (us) = 734.557861328125
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dt (us) = 10617.233642578125
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dt (us) = 9594.90576171875
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dt (us) = 9155.299560546875
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dt (us) = 9520.526611328125
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delayMicroseconds(2000)
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dt (us) = 8799.3056640625
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dt (us) = 9609.2685546875
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dt (us) = 9679.5439453125
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dt (us) = 9248.145263671875
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dt (us) = 9389.721923828125
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dt (us) = 9637.994262695312
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dt (us) = 9616.450073242188
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dt (us) = 9592.853881835938
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dt (us) = 9465.639892578125
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dt (us) = 7650.276611328125
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using GS_timing
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timing.delayMicroseconds(1)
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dt (us) = 53.3477783203125
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dt (us) = 36.93310546875
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dt (us) = 36.9329833984375
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dt (us) = 34.8812255859375
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dt (us) = 35.3941650390625
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dt (us) = 40.010986328125
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dt (us) = 38.4720458984375
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dt (us) = 56.425537109375
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dt (us) = 35.9072265625
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dt (us) = 36.420166015625
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timing.delayMicroseconds(2000)
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dt (us) = 2039.526611328125
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dt (us) = 2046.195068359375
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dt (us) = 2033.8841552734375
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dt (us) = 2037.4747314453125
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dt (us) = 2032.34521484375
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dt (us) = 2086.2059326171875
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dt (us) = 2035.4229736328125
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dt (us) = 2051.32470703125
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dt (us) = 2040.03955078125
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dt (us) = 2027.215576171875
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SAMPLE RESULTS ON MY RASPBERRY PI VERSION 1 B+:
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using time.sleep
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delayMicroseconds(1)
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dt (us) = 1022.0
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dt (us) = 417.0
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dt (us) = 407.0
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dt (us) = 450.0
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dt (us) = 2078.0
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dt (us) = 393.0
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dt (us) = 1297.0
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dt (us) = 878.0
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dt (us) = 1135.0
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dt (us) = 2896.0
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delayMicroseconds(2000)
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dt (us) = 2746.0
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dt (us) = 2568.0
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dt (us) = 2512.0
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dt (us) = 2423.0
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dt (us) = 2454.0
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dt (us) = 2608.0
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dt (us) = 2518.0
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dt (us) = 2569.0
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dt (us) = 2548.0
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dt (us) = 2496.0
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using GS_timing
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timing.delayMicroseconds(1)
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dt (us) = 572.0
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dt (us) = 673.0
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dt (us) = 1084.0
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dt (us) = 561.0
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dt (us) = 728.0
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dt (us) = 576.0
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dt (us) = 556.0
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dt (us) = 584.0
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dt (us) = 576.0
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dt (us) = 578.0
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timing.delayMicroseconds(2000)
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dt (us) = 2741.0
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dt (us) = 2466.0
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dt (us) = 2522.0
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dt (us) = 2810.0
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dt (us) = 2589.0
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dt (us) = 2681.0
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dt (us) = 2546.0
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dt (us) = 3090.0
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dt (us) = 2600.0
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dt (us) = 2400.0
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"""

‎test_import.py

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"""
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test.py
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By Gabriel Staples
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http://www.ElectricRCAircraftGuy.com
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-click "Contact me" at the top of my website to find my email address
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13 Aug. 2016
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"""
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import GS_timing as timing
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print(timing.micros())
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print(timing.millis())
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print('version = ' + timing.VERSION)
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print(timing._constrain(10,11,15)) #11

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