add RP2 and pyboard pin usage examples for RTU examples in documentat…

…ion, relates to brainelectronics#7 and brainelectronics#17

docs/EXAMPLES.md

@@ -27,8 +27,22 @@ RTU (serial/UART) to a requesting host device.
 from umodbus.serial import ModbusRTU
 
 # RTU Client/Slave setup
-# the following example is for an ESP32
+
+# the following definition is for an ESP32
 rtu_pins = (25, 26)         # (TX, RX)
+uart_id = 1
+
+# the following definition is for a RP2
+# rtu_pins = (Pin(0), Pin(1))     # (TX, RX)
+# uart_id = 0
+#
+# rtu_pins = (Pin(4), Pin(5))     # (TX, RX)
+# uart_id = 1
+
+# the following definition is for a pyboard
+# rtu_pins = (Pin(PB6), Pin(PB7))   # (TX, RX)
+# uart_id = 1
+
 slave_addr = 10             # address on bus as client
 
 client = ModbusRTU(
@@ -39,7 +53,7 @@ client = ModbusRTU(
     # stop_bits=1,          # optional, default 1
     # parity=None,          # optional, default None
     # ctrl_pin=12,          # optional, control DE/RE
-    # uart_id=1             # optional, see port specific documentation
+    uart_id=uart_id         # optional, default 1, see port specific documentation
 )
 
 register_definitions = {
@@ -95,8 +109,21 @@ setting data at a RTU (serial/UART) client/slave.
 from umodbus.serial import Serial as ModbusRTUMaster
 
 # RTU Host/Master setup
-# the following example is for an ESP32
+
+# the following definition is for an ESP32
 rtu_pins = (25, 26)         # (TX, RX)
+uart_id = 1
+
+# the following definition is for a RP2
+# rtu_pins = (Pin(0), Pin(1))     # (TX, RX)
+# uart_id = 0
+#
+# rtu_pins = (Pin(4), Pin(5))     # (TX, RX)
+# uart_id = 1
+
+# the following definition is for a pyboard
+# rtu_pins = (Pin(PB6), Pin(PB7))   # (TX, RX)
+# uart_id = 1
 
 host = ModbusRTUMaster(
     pins=rtu_pins,          # given as tuple (TX, RX)
@@ -105,7 +132,7 @@ host = ModbusRTUMaster(
     # stop_bits=1,          # optional, default 1
     # parity=None,          # optional, default None
     # ctrl_pin=12,          # optional, control DE/RE
-    # uart_id=1             # optional, see port specific documentation
+    uart_id=uart_id         # optional, default 1, see port specific documentation
 )
 
 coil_status = host.read_coils(slave_addr=10, starting_addr=123, coil_qty=1)