计划是让几个IO例程“并发”运行(特别是在Raspberry Pi上,操作IO引脚并同时运行SPI接口)。我尝试使用asyncio来实现这一点。然而,我的简单试用拒绝运行。
这是代码的简化版本,省略了IO pin详细信息:
"""\
Reduced problem representation:
this won't run because GPIO details have been left out
"""
import RPi.GPIO as gpio
import asyncio
GPIO_PB = 12 # Define pushbutton channel
async def payload():
""" Provides some payload sequence using asyncio.sleep() """
#Payload action
await asyncio.sleep(1)
#Payload action
await asyncio.sleep(1)
class IOEvent(asyncio.locks.Event):
"""\
Create an Event for asyncio, fired by a callback from GPIO
The callback must take a single parameter: a gpio channel number
"""
def __init__(self, ioChannel, loop):
super().__init__(loop = loop)
self.io = ioChannel
def get_callback(self):
"The callback is a closure that knows self when called"
def callback( ch ):
print("callback for channel {}".format(ch))
if ch == self.io and not self.is_set():
print(repr(self))
self.set()
print(repr(self))
return callback
async def Worker(loop, event):
print("Entering Worker: {}".format(repr(loop)))
while loop.is_running():
print("Worker waiting for {}".format(repr(event)))
await event.wait()
print("Worker has event")
event.clear()
await payload()
print("payload ended")
loop = asyncio.get_event_loop()
# Create an event for the button
pb_event = IOEvent( GPIO_PB, loop)
# register the pushbutton's callback
# Pushing the button calls this callback function
gpio.add_event_callback( GPIO_PB, pb_event.get_callback() )
try:
asyncio.ensure_future(Worker(loop, pb_event))
loop.run_forever()
except KeyboardInterrupt:
pass
finally:
print("Closing Loop")
loop.stop()
loop.close()
我得到的输出如下:
Entering Worker: <_UnixSelectorEventLoop running=True closed=False debug=False>
Worker waiting for <__main__.IOEvent object at 0x76a2a950 [unset]>
callback for channel 12
<__main__.IOEvent object at 0x76a2a950 [unset,waiters:1]>
<__main__.IOEvent object at 0x76a2a950 [set,waiters:1]>
callback for channel 12
这些行显示按钮重复且正确地触发其回调例程。第一次调用
set()
功能如预期。用于
wait()
电话和
集合()
通话内容相同。但是信息
“工作进程有事件”
await event.wait()
呼叫从未出现。
我看着
PyQt5 and asyncio: yield from never finishes
,但除了默认循环之外,我看不到任何其他循环。
为什么
等待()
永远不回来?我怎么知道?