cederom doc uart update 20220818

docs/esp32/quickref.rst

@@ -216,9 +216,10 @@ They each have default GPIO assigned to them, however depending on your
 ESP32 variant and board, these pins may conflict with embedded flash,
 onboard PSRAM or peripherals.
 
-Any GPIO can be used for hardware UARTs using the GPIO matrix, so to avoid
-conflicts simply provide ``tx`` and ``rx`` pins when constructing. The default
-pins listed below.
+Any GPIO can be used for hardware UARTs using the GPIO matrix, except for
+input-only pins 34-39 that can be used as ``rx``. To avoid conflicts simply
+provide ``tx`` and ``rx`` pins when constructing. The default pins listed
+below.
 
 =====  =====  =====  =====
 \      UART0  UART1  UART2

docs/library/machine.UART.rst

@@ -87,10 +87,22 @@ Methods
        When no pins are given, then the default set of TX and RX pins is taken, and hardware
        flow control will be disabled. If *pins* is ``None``, no pin assignment will be made.
 
+   .. note::
+     It is possible to call ``init()`` multiple times on the same object in
+     order to reconfigure  UART on the fly. That allows using single UART
+     peripheral to serve different devices attached to different GPIO pins.
+     Only one device can be served at a time in that case.
+     Also do not call ``deinit()`` as it will prevent calling ``init()``
+     again. Tested on ESP32.
+
 .. method:: UART.deinit()
 
    Turn off the UART bus.
 
+   .. note::
+     You will not be able to call ``init()`` on the object after ``deinit()``.
+     A new instance needs to be created in that case.
+
 .. method:: UART.any()
 
    Returns an integer counting the number of characters that can be read without