Added support for I2C MCP9808 sensor (closes #4) based on https://github.com/ControlEverythingCommunity/MCP9808/blob/master/Python/MCP9808.py

plugins/check_temperature

@@ -2,10 +2,10 @@
 #
 # check_temperature - Nagios temperature check for DS18B20 sensor on RaspberryPi
 #
-# Version 1.1, latest version, documentation and bugtracker available at:
+# Version 1.2, latest version, documentation and bugtracker available at:
 #              https://gitlab.lindenaar.net/scripts/nagios-plugins
 #
-# Copyright (c) 2017 Frederik Lindenaar
+# Copyright (c) 2017 - 2019 Frederik Lindenaar
 #
 # This script is free software: you can redistribute and/or modify it under the
 # terms of version 3 of the GNU General Public License as published by the Free
@@ -27,15 +27,21 @@ from argparse import ArgumentParser as StandardArgumentParser, FileType, \
 import logging
 
 # Constants (no need to change but allows for easy customization)
-VERSION="1.1"
+VERSION="1.2"
 PROG_NAME=splitext(basename(__file__))[0]
 PROG_VERSION=PROG_NAME + ' ' + VERSION
-SENSOR_SCALE=1000
+
+CPU_SENSOR_DEV = '/sys/class/thermal/thermal_zone0/temp'
+I2C_MCP9808_CONFIG_ADDR=0x1
+I2C_MCP9808_CONFIG = [ 0x00, 0x00 ]  # continuous conversion (power-up default)
+I2C_MCP9808_PRECISION_ADDR=0x08
+I2C_MCP9808_PRECISION=3	             # 0=0.5, 1=0.25, 2=0.125, 3=0.0625 degr. C
+I2C_MCP9808_TEMP_ADDR=0x05
 W1_SENSOR_DEV_DIR =  '/sys/bus/w1/devices/'
 W1_SENSOR_DEV_PREFIX = '28-'
 W1_SENSOR_DEV_SUFFIX = '/w1_slave'
 W1_SENSOR_READ_RETRIES=10
-CPU_SENSOR_DEV = '/sys/class/thermal/thermal_zone0/temp'
+W1_SENSOR_SCALE=1000
 
 LOG_FORMAT='%(levelname)s - %(message)s'
 LOG_FORMAT_FILE='%(asctime)s - ' + LOG_FORMAT
@@ -81,15 +87,15 @@ class SetLogFile(StoreAction):
 
 ###############################################################################
 
-def convert_celcius(temp_read):
+def convert_celcius(temp_read, scale = 1):
     """Converts raw temperature sensore value to degrees Celcius"""
-    return float(temp_read) / float(SENSOR_SCALE)
+    return float(temp_read) / float(scale)
 CONVERT_CELCIUS = ( convert_celcius, 'C', 'Celcius' )
 
 
-def convert_farenheit(temp_read):
+def convert_farenheit(temp_read, scale = 1):
     """Converts raw temperature sensore value to degrees Farenheit"""
-    return float(temp_read * 9) / float(5 * SENSOR_SCALE) + 32.0
+    return float(temp_read * 9) / float(5 * scale) + 32.0
 CONVERT_FARENHEIT = ( convert_farenheit, 'F', 'Farenheit' )
 
 
@@ -98,6 +104,11 @@ def isempty(string):
     return string is None or len(string) == 0
 
 
+def hex_int(string):
+    """Use int()'s auto-detection to parse 10-base and 16-base (0x..) numbers"""
+    return int(string, 0);
+
+
 def read_rpi_cpu_temp(args):
     """Reads CPU temperature and converts it to desired unit, returns temperature"""
     with open(args.file, 'r') as f:
@@ -111,6 +122,51 @@ def read_rpi_cpu_temp(args):
     return temp, 1
 
 
+def read_i2c_mcp9808_temp(args):
+    """Returns temperature from I2C MCP9808 sensor in desired unit"""
+
+    try:
+        import smbus
+    except ImportError:
+        try:
+            import smbus2 as smbus
+        except ImportError:
+            logger.critical("Unable to import either smbus or smbus2 library");
+            raise ImportError("missing I2C library, please install python-smbus or smbus2");
+
+    try:
+        bus = smbus.SMBus(args.i2cbus) # Get I2C bus
+    except OSError as e:
+        logger.critical(e)
+        raise IOError("Invalid I2C bus: %d" % args.i2cbus)
+
+    try:
+        bus.write_i2c_block_data(args.address, I2C_MCP9808_CONFIG_ADDR,
+                                               I2C_MCP9808_CONFIG)
+        bus.write_byte_data(args.address, I2C_MCP9808_PRECISION_ADDR,
+                                          I2C_MCP9808_PRECISION)
+        sleep(0.5)
+
+        # Read temperature (0x05), 2 bytes (MSB, LSB)
+        data = bus.read_i2c_block_data(args.address, I2C_MCP9808_TEMP_ADDR, 2)
+        logger.debug('Temperature sensor data from MCP9808 %#02x: 0x%02x%02x',
+                     args.address, data[0], data[1])
+
+        # Convert the data to 13-bits
+        temp_read = ((data[0] & 0x1F) * 256) + data[1]
+        if temp_read > 4095 :
+            temp_read -= 8192
+
+        temp = args.converter[0](temp_read, 16)
+        logger.debug('Temperature sensor value %d is %.2f%s',
+                     temp_read, temp, args.converter[1])
+        return temp, 1
+    except IOError as e:
+        logger.critical(e)
+        raise IOError("Error while communicating with I2C device %#02x" %
+                      args.address)
+
+
 def get_w1_sensor_device_filename(args, dev_dir=W1_SENSOR_DEV_DIR,
                             prefix=W1_SENSOR_DEV_PREFIX, suffix=W1_SENSOR_DEV_SUFFIX):
     """Auto-determine sensor datafile name (unless args.file is set)"""
@@ -138,8 +194,8 @@ def get_w1_sensor_device_filename(args, dev_dir=W1_SENSOR_DEV_DIR,
     return filename
 
 
-def read_w1_temp(args):
+def read_w1_ds18b20_temp(args):
-    """Reads sensor data and converts it to desired unit, returns temperature"""
+    """Returns temperature from 1-wire ds18b20 sensor in desired unit"""
     device_file = get_w1_sensor_device_filename(args)
     lines=[ '' ]
     tries = 0
@@ -160,7 +216,7 @@ def read_w1_temp(args):
             errmsg = 'temperature sensor data format is not supported'
         else:
             temp_read = int(lines[1][equals_pos+2:])
-            temp = args.converter[0](temp_read)
+            temp = args.converter[0](temp_read, W1_SENSOR_SCALE)
             logger.debug('Temperature sensor value %d is %.2f%s', temp_read,
                          temp, args.converter[1])
             return temp, tries
@@ -174,11 +230,7 @@ def parse_args():
 
     # Setup argument parser, the workhorse gluing it all together
     parser = ArgumentParser(
-        epilog='(*) by default the script will look for the first device that '
+        description='Nagios check plugin for temperature sensors on RaspberryPi'
-               'matches %s* in %s, if multiple entries are found -s or -f must '
-               'be used to specify which sensor to read.' %
-               (W1_SENSOR_DEV_PREFIX, W1_SENSOR_DEV_DIR),
-        description='Nagios check plugin for 1-wire temp. sensor on RaspberryPi'
     )
     parser.add_argument('-V', '--version',action="version",version=PROG_VERSION)
 
@@ -218,6 +270,16 @@ def parse_args():
                                     help='read built-in Raspberry Pi CPU temperature')
     cmdparser.set_defaults(func=read_rpi_cpu_temp, cmdparser=cmdparser, retries=0)
 
+    i2cparser = ArgumentParser(add_help=False)
+    i2cparser.add_argument('-a', '--address', type=hex_int,
+                           help='I2C Address of sensor, use 0x.. for hex (*)')
+    i2cparser.add_argument('-b', '--i2cbus', default=1, type=int,
+                           help='I2C Bus to use (defaults to 1)')
+    cmdparser = subparser.add_parser('i2c_mcp9808', parents=[i2cparser],
+             help='read I2C connected MCP9808 sensor',
+             epilog='(*) default I2C address for an MCP9808 is 0x18')
+    cmdparser.set_defaults(func=read_i2c_mcp9808_temp, cmdparser=cmdparser, retries=0, address=0x18)
+
     w1parser = ArgumentParser(add_help=False)
     pgroup = w1parser.add_mutually_exclusive_group(required=False)
     pgroup.add_argument('-s', '--serial',
@@ -228,8 +290,12 @@ def parse_args():
                         help='number of times to retry reading sensor data when'
                              ' unstable (defaults to %d)' % W1_SENSOR_READ_RETRIES)
     cmdparser = subparser.add_parser('w1_ds18b20', parents=[w1parser],
-                                    help='read 1-wire connected DS18b20 sensor')
+                                    help='read 1-wire connected DS18b20 sensor',
-    cmdparser.set_defaults(func=read_w1_temp,   cmdparser=cmdparser)
+        epilog='(*) by default the script will look for the first device that '
+               'matches %s* in %s, if multiple entries are found -s or -f must '
+               'be used to specify which sensor to read.' %
+               (W1_SENSOR_DEV_PREFIX, W1_SENSOR_DEV_DIR))
+    cmdparser.set_defaults(func=read_w1_ds18b20_temp,   cmdparser=cmdparser)
 
     # parse arguments and post-process command line options
     args = parser.parse_args()
@@ -268,7 +334,7 @@ if __name__ == '__main__':
     except (KeyboardInterrupt) as e:
         nagios_exit(NAGIOS_UNKNOWN,'temperature sensor read aborted by user')
 
-    except (IOError, ValueError) as e:
+    except (IOError, ValueError, ImportError) as e:
         nagios_exit(NAGIOS_UNKNOWN,'temperature sensor read failed: %s' % e)
 
     elapse = endtime-starttime