TUTORIAL.md, auart.py: Add timeout value.

Author: peterhinch

v3/as_demos/auart.py

@@ -1,11 +1,11 @@
 # Test of uasyncio stream I/O using UART
 # Author: Peter Hinch
-# Copyright Peter Hinch 2017-2020 Released under the MIT license
+# Copyright Peter Hinch 2017-2022 Released under the MIT license
 # Link X1 and X2 to test.
 
 import uasyncio as asyncio
 from machine import UART
-uart = UART(4, 9600)
+uart = UART(4, 9600, timeout=0)
 
 async def sender():
     swriter = asyncio.StreamWriter(uart, {})

v3/docs/TUTORIAL.md

@@ -2053,7 +2053,7 @@ demonstrates concurrent I/O on one UART. To run, link Pyboard pins X1 and X2
 ```python
 import uasyncio as asyncio
 from machine import UART
-uart = UART(4, 9600)
+uart = UART(4, 9600, timeout=0)  # timeout=0 prevents blocking at low baudrates
 
 async def sender():
     swriter = asyncio.StreamWriter(uart, {})