#!/usr/bin/env python3 # devtimer.py - Temperature Controlled Photographic Darkroom Timer # Targeted for RaspberryPi # Copyright (c) 2018 TundraWare Inc. # Permission Hereby Granted For Unrestricted Personal Or Commercial Use from threading import Thread from time import time, sleep from tm1637 import * from wiringpi import wiringPiSetupGpio ##### # Constants ##### # Display BRIGHTNESS0 = 0x09 CLK0 = 21 DIO0 = 20 # General Constants DEBUG = True # Debugging switch BEEP = 15 # Beep interval CALIBRATION_OFFSET = 0.003 # Compensate for program overhead in master loop # Profile Constants REALTIME = 0 PAPER = 1 FILM = 2 # Globals # These get updated by the threads that read the switches and # thermocouple. On a slow machine like the Pi Zero, we want to avoid # unnecessary function calls, so we make these globally RW. # So, shoot me ... CURRENT_PROFILE = FILM CURRENT_TEMP = 20 # Stored as index relative to 60F ##### # Lookup Table For Compensating Factors ##### ''' There are 3 tables in the list below. In order: Realtime Paper Film Each contains entires for multiplicative corrections from 60F to 80F. The profile global above selects which of these tuples to index into - using the normalized temp global above as the index. We don't want to use a dictionary here (with profile as the key) because of the overhead that incurs. Straight tuple indexing should be much quicker. WARNING: It takes about 250ms to update the display on a Pi Zero. So, if the "virtual second" falls at or below this, the code will be attempting to do updates faster than the display can handle. So ... the total compensation cannot reduce the virtual second to less than about 0.300 to be on the safe side. ''' compensate = ( (1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000, 1.000), (1.724, 1.611, 1.505, 1.406, 1.313, 1.227, 1.146, 1.070, 1.000, 0.934, 0.873, 0.815, 0.762, 0.711, 0.665, 0.621, 0.580, 0.542, 0.506, 0.473, 0.442), (1.445, 1.380, 1.318, 1.259, 1.202, 1.148, 1.096, 1.047, 1.000, 0.955, 0.912, 0.871, 0.832, 0.795, 0.759, 0.725, 0.692, 0.661, 0.631, 0.603, 0.576) ) # Beep at the user at fixed intervals def beep(): print("Beep!") # Update the display with elapsed time def show_elapsed(display0, elapsed): min = elapsed // 60 sec = elapsed % 60 d0 = display0.digit_to_segment[min // 10] d1 = display0.digit_to_segment[min % 10] d2 = display0.digit_to_segment[sec // 10] d3 = display0.digit_to_segment[sec % 10] display0.set_segments([d0, 0x80 + d1, d2, d3]) ##### # Program entry point ##### ''' Notice that the actual updating of the display gets run on its own thread. That's because - on a Pi Zero, at least - it takes over 250ms to do this. We don't want that time added to our timing loop, so we send it off on a parallel thread, and initiate timing for the next round in this thread. ''' if __name__ == "__main__": # Setup the hardware wiringPiSetupGpio() display0 = TM1637(CLK0, DIO0, BRIGHTNESS0) # Start timing, using the selected profile and measured temperature elapsed_time = 0 while True: # Beep periodically if not elapsed_time % BEEP: beep() if DEBUG: last = time() update_thread = Thread(None, show_elapsed, None, (display0, elapsed_time)) sleep(compensate[CURRENT_PROFILE][CURRENT_TEMP] - CALIBRATION_OFFSET) elapsed_time += 1 elapsed_time %= 6000 update_thread = Thread(None, show_elapsed, None, (display0, elapsed_time)) if DEBUG: print("Current Temp: %s Inter-update Time: %s" % (CURRENT_TEMP, str(time()-last))) update_thread.start()