Add example pyHydrabus I2C (using clock stretching feature) with SHT3…

…x I2C Sensirion Humidity and Temperature Sensor

contrib/pyHydra_SHT3x/README.md

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+Script to communicate with Hydrabus to I2C Sensirion Humidity and Temperature Sensor (SHT30, SHT31, SHT35).
+
+The script uses the pyHydrabus library.
+This script requires Python 3.2+
+
+Dependencies:
+pip3 install serial
+
+Author: Benjamin Vernoux <[email protected]>
+
+License: GPLv3 (https://choosealicense.com/licenses/gpl-3.0/)
+
+(if license conflicts with hydrafw license, hydrafw license prevails)

contrib/pyHydra_SHT3x/hydra_SHT3x.py

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+#!/usr/bin/env python3
+#
+# Script to communicate to I2C Sensirion Humidity and Temperature Sensor (SHT30, SHT31, SHT35)
+#
+# Author: Benjamin Vernoux <[email protected]>
+# License: GPLv3 (https://choosealicense.com/licenses/gpl-3.0/)
+#
+import sys
+import time
+from pyHydrabus import I2C
+
+class SHT3x(I2C):
+ """
+ I2C Sensirion Humidity and Temperature Sensor (SHT30, SHT31, SHT35)
+ """
+ def __init__(self, port="", i2c_addr_7bits=0x44):
+ """
+ Handler constructor
+ :param i2c_addr_7bits: I2C Addr 7bits
+ """
+ SHT3X_ACK_TIME_MAX_MILLISEC = 20
+ I2C_CLK_STRETCH = int((SHT3X_ACK_TIME_MAX_MILLISEC/(1/400))) # 20ms max @400KHz
+ super().__init__(port)
+ self.set_speed(self.I2C_SPEED_400K)
+ self.pullup=0 # Use external 10K pull-up
+ self.clock_stretch(I2C_CLK_STRETCH)
+ self.i2c_addr_write_8b = (i2c_addr_7bits << 1)
+ self.i2c_addr_read_8b = self.i2c_addr_write_8b + 1
+
+ def read_data(self):
+ data1 = self.i2c_addr_write_8b.to_bytes(1, byteorder="big") + b'\x2c\x06'
+ self.write(data1);
+ data2= self.i2c_addr_read_8b.to_bytes(1, byteorder="big")
+ data = self.write_read(data2, 6)
+ #print(data1, len(data1))
+ #print(data2, len(data2))
+ #print(data, len(data))
+ cTemp=0
+ humidity=0
+ if (data is not None):
+ cTemp = ((((data[0] * 256.0) + data[1]) * 175) / 65535.0) - 45
+ humidity = ((((data[3] * 256.0) + data[4]) * 100) / 65535.0)
+ return cTemp, humidity
+
+if __name__ == '__main__':
+ args = sys.argv[1:]
+ #sht3x = SHT3x('/dev/ttyACM0')
+ sht3x = SHT3x('COM7')
+ iterations = 0
+ if len(args) > 0:
+ iterations = int(args[0])
+ if iterations < 1:
+ iterations = 1
+ for x in range(iterations):
+ cTemp, humidity = sht3x.read_data()
+ print("T(°C)="+"{:.2f}".format(cTemp)+" Humidity(%)="+"{:.2f}".format(humidity))
+ time.sleep(0.25)