Merge remote-tracking branch 'trio/master'

Author: smurfix

examples/push_button_event.py

@@ -0,0 +1,88 @@
+import time
+import trio
+import trio_gpio as gpio
+
+"""
+This example is taken out of my furnace controller.
+It has been tested with Raspberry Pi Zero W and I assume it will work with any board supported by trio_gpio.
+Use at your own risk.
+
+If you aren't sure about how to hook up a button and led to your board, there are a lot of examples online.
+
+Thank you @smurfix, who wrote trio_gpio and @njsmith and other in glitter:python-trio/general room
+who helped me out.
+"""
+
+
+class Led:
+	# This class turns on and off the power to a pin.
+	# Two events are setup for turning off an on the pin. Both events need to be 
+	# called at the same time or trio might await at the wrong spot.
+	def __init__(self, line):
+		self.x = line
+		self._on = trio.Event()
+		self._off = trio.Event()
+
+	async def liteon(self):
+		with gpio.open_chip() as chip:
+			with chip.line(self.x).open(direction=gpio.DIRECTION_OUTPUT) as line:
+				self._on.clear()
+				self._off.set()
+				while True:
+					if self._on.is_set():
+						line.value = 1
+						# print('lite on')
+						await self._off.wait()
+						self._on.clear()
+					elif self._off.is_set():
+						line.value = 0
+						# print('lite off')d
+						await self._on.wait()
+						self._off.clear()
+					else:
+						# should never be reached.
+						# if the code does reach here,
+						# turn off the power to whatever is being powered
+						print('error: both are off.')
+						self._off.set()
+
+
+class Button:
+	# Add the events tthe button is attached to and the on off event are passed into the class.
+	# The class listens for the voltage to rise then reverses whatever the current settings are.
+	def __init__(self, line, event_on, event_off):
+		self.y = line
+		self._on = event_on
+		self._off = event_off
+
+	async def push(self):
+		with gpio.Chip(0) as c:
+			in_ = c.line(self.y)
+			with in_.monitor(gpio.REQUEST_EVENT_RISING_EDGE):
+				last = 0
+				async for e in in_:
+					# This section is for debouncing the button.
+					# As a button is pushed and released the voltage can rapidly go up and down many times
+					# when the user only meant one push. To limit this, a delay is add to ignore changes.
+					# This can be adjusted depending on the button and the respose.
+					secs, ns_secs = e.timestamp
+					now = float(str(secs)+'.'+str(ns_secs))
+					if now >= last + .25:
+						print('button', e.value, secs, ns_secs, now)
+						self._off.set() if self._on.is_set() else self._on.set()
+					last = now
+
+# Trio-gpio uses the BCM pin numbering. So, the led is on the pin 21 
+# and the button that controls the yellow is hooked to pin 23.
+yellow = Led(21) 
+yellowbutton = Button(23, yellow._on, yellow._off)
+
+
+async def main(y):
+	async with trio.open_nursery() as nursery:
+		nursery.start_soon(yellowbutton.push)
+		nursery.start_soon(yellow.liteon)
+
+
+if __name__ == "__main__":
+    trio.run(main, 1)