1  # SPDX-FileCopyrightText: 2021 Liz Clark for Adafruit Industries
 2  #
 3  # SPDX-License-Identifier: MIT
 4  
 5  import time
 6  import board
 7  import adafruit_scd4x
 8  import sdcardio
 9  import busio
10  import storage
11  import adafruit_pcf8523
12  
13  #  setup for I2C
14  i2c = board.I2C()
15  #  setup for SCD40
16  scd4x = adafruit_scd4x.SCD4X(i2c)
17  #  setup for RTC
18  rtc = adafruit_pcf8523.PCF8523(i2c)
19  #  start measuring co2 with SCD40
20  scd4x.start_periodic_measurement()
21  #  list of days to print to the text file on boot
22  days = ("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday")
23  
24  # SPI SD_CS pin
25  SD_CS = board.D10
26  
27  #  SPI setup for SD card
28  spi = busio.SPI(board.SCK, board.MOSI, board.MISO)
29  sdcard = sdcardio.SDCard(spi, SD_CS)
30  vfs = storage.VfsFat(sdcard)
31  try:
32      storage.mount(vfs, "/sd")
33      print("sd card mounted")
34  except ValueError:
35      print("no SD card")
36  
37  #  to update the RTC, change set_clock to True
38  #  otherwise RTC will remain set
39  #  it should only be needed after the initial set
40  #  if you've removed the coincell battery
41  set_clock = False
42  
43  if set_clock:
44      #                     year, mon, date, hour, min, sec, wday, yday, isdst
45      t = time.struct_time((2021,  10,   31,   00,  00,  00,    0,   -1,    -1))
46  
47      print("Setting time to:", t)
48      rtc.datetime = t
49      print()
50  
51  #  variable to hold RTC datetime
52  t = rtc.datetime
53  
54  time.sleep(1)
55  
56  #  initial write to the SD card on startup
57  try:
58      with open("/sd/co2.txt", "a") as f:
59          #  writes the date
60          f.write('The date is {} {}/{}/{}\n'.format(days[t.tm_wday], t.tm_mday, t.tm_mon, t.tm_year))
61          #  writes the start time
62          f.write('Start time: {}:{}:{}\n'.format(t.tm_hour, t.tm_min, t.tm_sec))
63          #  headers for data, comma-delimited
64          f.write('CO2,Time\n')
65          #  debug statement for REPL
66          print("initial write to SD card complete, starting to log")
67  except ValueError:
68      print("initial write to SD card failed - check card")
69  
70  while True:
71      try:
72          #  variable for RTC datetime
73          t = rtc.datetime
74          #  append SD card text file
75          with open("/sd/co2.txt", "a") as f:
76              #  read co2 data from SCD40
77              co2 = scd4x.CO2
78              #  write co2 data followed by the time, comma-delimited
79              f.write('{},{}:{}:{}\n'.format(co2, t.tm_hour, t.tm_min, t.tm_sec))
80              print("data written to sd card")
81          #  repeat every 30 seconds
82          time.sleep(30)
83      except ValueError:
84          print("data error - cannot write to SD card")
85          time.sleep(10)