Instrument control package: Difference between revisions

Instrument control package (edit)

1,244 bytes added , 12 January 2020

Anonymous user

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 == i2c ==
-i2c
+Example with a Si7021 i2c breakout board (https://www.sparkfun.com/products/1376) connected to a i2c master interface.
+To work out the devices available (assuming i2ctools are installed) run the i2cdetect command from a terminal window.
+$ i2cdetect -l
+i2c-1   i2c             i2c-ch341-usb at bus 002 device 008     I2C adapter
+i2c-0   unknown         SMBus I801 adapter at 4000              N/
+In the example case the temperature sensor is connected to the i2c-ch341-usb device, as as sufficient permissions to access the device as a user.
+Accoridng to the datasheet, the temperature device uses address 0x40, so create a i2c device using the linux device and address:
+i2cdev = i2c("/dev/i2c-1", 0x40)
+To read  the termaturem register 0xF3 must be addressed and read (2 bytes of data):
+TEMP_MEASURE_NOHOLD = hex2dec("F3");
+fwrite (i2cdev, uint8([TEMP_MEASURE_NOHOLD]));
+pause (0.02);
+data = fread (i2cdev, 3);
+The data needs to be converted to a 16 bit value and the unused part masked out.
+value = uint16(data(1))*256 + uint16(data(2));
+value = bitand (value, hex2dec("FFFC"));
+temp_Code = double(value);
+Now convert the temperature to degrees C and display:
+C = (175.72*temp_Code/65536)-46.85;
+printf ("temperature read %f C\n", C);
 == TCP ==