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C/SI7006_A20.c

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+// Distributed with a free-will license.
+// Use it any way you want, profit or free, provided it fits in the licenses of its associated works.
+// SI7006-A20
+// This code is designed to work with the SI7006-A20_I2CS I2C Mini Module available from ControlEverything.com.
+// https://www.controleverything.com/content/Humidity?sku=SI7006-A20_I2CS#tabs-0-product_tabset-2
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <linux/i2c-dev.h>
+#include <sys/ioctl.h>
+#include <fcntl.h>
+
+void main()
+{
+	// Create I2C bus
+	int file;
+	char *bus = "/dev/i2c-1";
+	if((file = open(bus, O_RDWR)) < 0) 
+	{
+		printf("Failed to open the bus. \n");
+		exit(1);
+	}
+	// Get I2C device, SI7006-A20 I2C address is 0x40(64)
+	ioctl(file, I2C_SLAVE, 0x40);
+
+	// Send humidity measurement command, NO HOLD MASTER(0xF5)
+	char config[1] = {0xF5};
+	write(file, config, 1); 
+	sleep(1);
+
+	// Read 2 bytes of humidity data
+	// humidity msb, humidity lsb
+	char data[2] = {0};
+	if(read(file, data, 2) != 2)
+	{
+		printf("Erorr : Input/output Erorr \n");
+	}
+	else
+	{
+		// Convert the data
+		float humidity = (((data[0] * 256 + data[1]) * 125.0) / 65536.0) - 6;
+
+		// Output data to screen
+		printf("Relative Humidity : %.2f RH \n", humidity);
+	}
+
+	// Send temperature measurement command, NO HOLD MASTER(0xF3)
+	config[0] = 0xF3;
+	write(file, config, 1); 
+	sleep(1);
+
+	// Read 2 bytes of temperature data
+	// temp msb, temp lsb
+	if(read(file, data, 2) != 2)
+	{
+		printf("Erorr : Input/output Erorr \n");
+	}
+	else
+	{
+		// Convert the data
+		float cTemp = (((data[0] * 256 + data[1]) * 175.72) / 65536.0) - 46.85;
+		float fTemp = cTemp * 1.8 + 32;
+
+		// Output data to screen
+		printf("Temperature in Celsius : %.2f C \n", cTemp);
+		printf("Temperature in Fahrenheit : %.2f F \n", fTemp);
+	}
+}