Update pycoax documentation

pycoax/README.md

@@ -2,8 +2,69 @@
 
 Python IBM 3270 coaxial interface library.
 
-## Use
+## Usage
 
-You will need to build a [interface](../interface1) and connect it to your computer.
+You will need to build an [interface](../interface1) and connect it to your computer.
+
+Install using `pip`:
+
+```
+pip install pycoax
+```
+
+Assuming your interface is connected to `/dev/ttyACM0` and you have a CUT type terminal connected to the interface, you can do something like this:
+
+```
+import time
+from serial import Serial
+from coax import SerialInterface, poll, poll_ack, load_address_counter_hi, \
+                 load_address_counter_lo, write_data, ReceiveTimeout
+
+with Serial('/dev/ttyACM0', 115200) as serial:
+    # Give the interface time to wake up...
+    time.sleep(3)
+
+    # Initialize and reset the interface.
+    interface = SerialInterface(serial)
+
+    firmware_version = interface.reset()
+
+    print(f'Firmware version is {firmware_version}')
+
+    # Wait for a terminal to attach...
+    poll_response = None
+    attached = False
+
+    while not attached:
+        try:
+            poll_response = poll(interface, receive_timeout=1)
+
+            if poll_response:
+                print(poll_response)
+
+                poll_ack(interface)
+
+            attached = True
+        except ReceiveTimeout:
+            print('.')
+
+            time.sleep(1)
+
+    # Poll the terminal until status is empty.
+    while poll_response:
+        poll_response = poll(interface)
+
+        if poll_response:
+            print(poll_response)
+
+            poll_ack(interface)
+
+    # Move the cursor to top-left cell of a 80 column display.
+    load_address_counter_hi(interface, 0)
+    load_address_counter_lo(interface, 80)
+
+    # Write a secret message.
+    write_data(interface, bytes.fromhex('a1 84 00 92 94 91 84 00 93 8e 00 83 91 88 8d 8a 00 98 8e 94 91 00 ae 95 80 8b 93 88 8d 84'))
+```
 
 See [examples](examples) for complete examples.