Initial commit for version 1.0

README.md

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+py-am2315 is a Python 3 library that reads temeperature and humidity data from the AOSONG AM2315 encased I2C temeperature and humidity sensor.
+
+Requires the quick2Wire (https://github.com/quick2wire/quick2wire-python-api) library to run, and the i2c-dev module loaded.

am2315.py

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+# am2315 class by ThreeSixes (https://github.com/ThreeSixes/py-am2315)
+# This was originally part of the OpenWeatherStn project (https://github.com/ThreeSixes/OpenWeatherStn)
+
+###########
+# Imports #
+###########
+
+import time
+import quick2wire.i2c as qI2c
+
+################
+# am2315 class #
+################
+
+class am2315:
+ """
+ am2315 is a class that supports communication with an I2C-connected AOSONG AM2315 encased temperature and humidity sensor. The constructor for this class accepts one argement:
+ 
+ am3215Addr: I2C address of the sensor, but will default to 0x5c if it's not specified.
+ """
+
+ # The config variables are based on the AM2315 datasheet
+ #
+
+ def __init__(self, am2315Addr = 0x5c):
+ # Set up I2C libraries
+ self.__i2c = qI2c
+ self.__i2cMaster = qI2c.I2CMaster()
+
+ # Set global address var
+ self.__addr = am2315Addr
+
+ # AM2315 Registers
+ self.regRhMSB = 0x00
+ self.regRhLSB = 0x01
+ self.regTmpMSB = 0x02
+ self.regTmpLSB = 0x03
+ self.regModelHi = 0x08
+ self.regModelLo = 0x09
+ self.regVersion = 0x0a
+ self.regIDA = 0x0b
+ self.regIDB = 0x0c
+ self.regIDD = 0x0d
+ self.regIDE = 0x0e
+ self.regStat = 0x0f
+ self.regUsrAMSB = 0x10
+ self.regUsrALSB = 0x11
+ self.regUsrBMSB = 0x12
+ self.regUsrBLSB = 0x13
+
+ # Commands
+ self.cmdReadReg = 0x03
+
+ def __getSigned(self, unsigned):
+ """
+ __getSigned(number)
+ 
+ Converts the temp reading from the AM2315 to a signed int. 
+ """
+
+ signednum = 0
+
+ # If we have the negative temp bit set
+ if (unsigned & 0x8000) == 0x8000:
+ # Clear the negative sign bit, and make the number negative.
+ signednum = 0 - (unsigned & 0x7fff)
+ else:
+ signednum = unsigned
+
+ # Return the unsigned int.
+ return signednum
+
+ def getTempHumid(self):
+ """
+ getTempHumid()
+ 
+ Get the temperature and humidity from the sensor. Returns an array with two integers - temp. [0] and humidity [1]
+ """
+
+ # Track temperature data.
+ tempRaw = 0
+ humidRaw = 0
+
+ # Raw temperature and humidity data.
+ rawTH = 0
+
+ # Return value
+ retVal = []
+
+ # Loop sentinel values
+ failCount = 0
+ notDone = True
+
+ # Commands to get data temp and humidity data from AM2315
+ thCmd = bytearray([0x00,0x04])
+
+ # If we have failed more than twice to read the data, or have finished getting data break the loop.
+ while ((failCount < 2) and notDone):
+
+ try:
+ # Request data from the sensor, using a reference to the command bytes.
+ self.__i2cMaster.transaction(self.__i2c.writing_bytes(self.__addr, self.cmdReadReg, *thCmd))
+
+ # Wait for the sensor to supply data to read.
+ time.sleep(0.1)
+
+ # Now read 8 bytes from the AM2315.
+ rawTH = self.__i2cMaster.transaction(self.__i2c.reading(self.__addr, 8))
+
+ # Break the string we want out of the array the transaction returns.
+ rawTH = bytearray(rawTH[0])
+
+ # Confirm the command worked by checking the response for the command we executed
+ # and the number of bytes we asked for.
+ if (rawTH[0] == self.cmdReadReg) and (rawTH[1] == 0x04):
+
+ # We're done. flag the loop to exit so we can interpret the data sent back to us.
+ notDone = False
+
+ # We usually fail to read data 50% of the time because the sensor goes to sleep, so try twice.
+ except IOError:
+ if failCount > 1:
+ raise IOError("am2315 IO Error: failed to read from sensor.")
+ else:
+ failCount = failCount + 1
+
+ # And the MSB and LSB for each value together to yield our raw values.
+ humidRaw = (rawTH[2] << 8) | rawTH[3]
+
+ # Get signed int from AND'd temperature bytes.
+ tempRaw = self.__getSigned((rawTH[4] << 8) | rawTH[5])
+
+ # The return data is sacled up by 10x, so compensate.
+ retVal.append(tempRaw / 10.0)
+ retVal.append(humidRaw / 10.0)
+
+ return retVal

am2315Test.py

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+# am2315Test.py by ThreeSixes (https://github.com/ThreeSixes/py-am2315)
+# This was originally part of the OpenWeatherStn project (https://github.com/ThreeSixes/OpenWeatherStn)
+
+###########
+# Imports #
+###########
+
+from am2315 import am2315
+import pprint
+
+#######################
+# Main execution body #
+#######################
+
+thSens = am2315()
+
+thDat = thSens.getTempHumid()
+
+print("Temperature: " + str(thDat[0]) + "C")
+print("Humidity: " + str(thDat[1]) + "%")