umqtt.simple: Add example to publish a message on button press.

umqtt.simple/example_pub_button.py

@@ -0,0 +1,30 @@
+import time
+import ubinascii
+import machine
+from umqtt.simple import MQTTClient
+from machine import Pin
+
+
+# Many ESP8266 boards have active-low "flash" button on GPIO0.
+button = Pin(0, Pin.IN)
+
+# Default MQTT server to connect to
+SERVER = "192.168.1.35"
+CLIENT_ID = ubinascii.hexlify(machine.unique_id())
+TOPIC = b"led"
+
+
+def main(server=SERVER):
+    c = MQTTClient(CLIENT_ID, server)
+    c.connect()
+    print("Connected to %s, waiting for button presses" % server)
+    while True:
+        while True:
+            if button.value() == 0:
+                break
+            time.sleep_ms(20)
+        print("Button pressed")
+        c.publish(TOPIC, b"toggle")
+        time.sleep_ms(200)
+
+    c.disconnect()