examples: add an example PCF8574 script

Author: attie-argentum

examples/i2c-pcf8574.py

@@ -0,0 +1,16 @@
+"""
+An example of a script that can be used with the run-script mode.
+
+This will read and write the pins of a PCF8574. Once connected, run:
+
+    glasgow run-script i2c-pcf8574.py i2c-initiator -V 3.3
+"""
+
+# read pin values
+print('I/O pin state: 0b{:08b}'.format((await iface.read(0x20, 1))[0]))
+
+# write pin values
+await iface.write(0x20, [ 0x55 ])
+
+# power down the device after use
+await device.set_voltage("AB", 0)