[英]Running different tasks simultaneously in python?
我編寫了一個python程序來在Raspberry Pi 3B +上連續執行以下操作:
該程序主要完成了我想要的操作,但是當我檢查.txt文件中的結果時,某些結果是“不可能的”,並指示我沒有正確讀取/轉換我的串行數據。 傳感器還以100電報/秒的速度輸出數據,這遠不及Raspberry Pi保存結果的實際速率(大約2次測量/秒)。
我嘗試編寫僅讀取串行數據的程序,而別的什么也不能讀取,並且可以跟上傳感器的速度。 我還嘗試用ser.read_until()替換對標頭的檢查(在每個電報的末尾保留無用的標頭)。 但是,這導致電報的長度不同,這使得對6個變量的解析更加困難。 檢查此鏈接,以查看根據規格組成的電報。 我現在(下面)使用的代碼以分段方式(2、2、1、1、2、2、1個字節)讀取電報,但有時返回的值似乎被誤解了。
#!/usr/bin/env python
import time, serial, os, sys, stat, os.path, subprocess
import RPi.GPIO as GPIO
from picamera import PiCamera
from datetime import datetime
ser = serial.Serial(
port='/dev/serial0',
baudrate = 19200,
parity=serial.PARITY_NONE,
stopbits=serial.STOPBITS_ONE,
bytesize=serial.EIGHTBITS,
timeout=0)
signaltrigger = 60
trigger = 24
GPIO.setmode(GPIO.BCM)
GPIO.setup(trigger, GPIO.IN, pull_up_down=GPIO.PUD_DOWN)
now = datetime.now()
data_dir = now.strftime("%d-%m-%Y")
save_path = "/home/pi/serial/"+data_dir+"/"
test = os.path.isdir(save_path)
if test == False:
os.mkdir(save_path)
subprocess.call(['chmod', '-R', '777', '/home/pi/serial'])
else:
pass
cam = PiCamera()
cam.rotation = 90
cam.resolution = (480, 360)
cam.start_preview()
signaltriggerA = 0
signaltriggerB = 0
while 1:
now = datetime.now()
time_exact = now.strftime(str(now)[11:23])
date_time = now.strftime("%d-%m-%Y %H:%M")
data_dir = now.strftime("%d-%m-%Y")
save_path = "/home/pi/serial/"+data_dir+"/"
completename = os.path.join(save_path, date_time+".txt")
namepic = str(time_exact+".jpg")
completenamepic = os.path.join(save_path, data_dir+" "+time_exact+".jpg")
test = os.path.isdir(save_path)
if test == False:
os.mkdir(save_path)
subprocess.call(['chmod', '-R', '777', '/home/pi/serial'])
pass
else:
pass
x = ser.read(3)
if x != b'~~~':
print("Header mismatched")
x = ser.read(9)
d = 0
j = 0
elif x == b'~~~':
print("Serial communication started...")
y = ser.read(2)
a = ser.read(2)
c = ser.read(1)
e = ser.read(2)
g = ser.read(2)
i = ser.read(1)
z = int.from_bytes(y, byteorder='little', signed=False)/100
b = round(int.from_bytes(a, byteorder='little', signed=True)*0.0367, 2)
d = int.from_bytes(c, byteorder='little', signed=False)
f = int.from_bytes(e, byteorder='little', signed=False)/100
h = round(int.from_bytes(g, byteorder='little', signed=True)*0.0367, 2)
j = int.from_bytes(i, byteorder='little', signed=False)
if d >= signaltrigger:
signaltriggerA = 1
else:
signaltriggerA = 0
if j >= signaltrigger:
signaltriggerB = 1
else:
signaltriggerB = 0
if signaltriggerA or signaltriggerB or GPIO.input(trigger):
cam.capture(completenamepic)
M = open(completename,"a+",encoding='utf-8')
M.write('[%s]: Distance(a) = %s [m], Velocity(a) = %s [km/h], Signal(a) = %s [dB], Distance(r) = %s [m], Velocity(r) = %s [km/h], Signal(r) = %s [dB]. Trigger(a) = %s, Trigger(r) = %s, Trigger(ETZ) = %s. Picture: %s\n'%(time_exact,z,b,d,f,h,j,signaltriggerA,signaltriggerB,GPIO.input(trigger),namepic))
M.close()
pass
else:
print("No triggers detected")
我希望程序將每個傳入的電報解析為6個部分,並將這些部分轉換為結果(整數或浮點數),但有時這些結果的值會變得過高(對於傳感器而言是不可能的)。 我希望這是由手動讀取不同的字節引起的(由於傳感器不斷吐出數據,因此花費了太多時間並丟失了電報的某些部分)。
如何確保正確讀取和轉換串行數據? 同樣,如果傳感器以每秒100封電報的速度輸出數據,但相機無法跟上每秒100張照片的速度,那么是否可以計算移動平均值而不是僅使用許多電報之一? 編輯:添加了電報規范的圖片,以幫助理解串行數據+添加了完整的python程序。
我將使用read_until()
讀取最多三個標頭字節,以及將數據字節轉換為值的更簡潔,更易讀的方法。
#!/usr/bin/env python3
from ctypes import LittleEndianStructure, c_int16, c_uint16, c_uint8, sizeof
from datetime import datetime
import os
class SensorData(LittleEndianStructure):
_pack_ = 1
_fields_ = [
('_distance', c_uint16),
('_velocity', c_int16),
('signal_strength', c_uint8),
]
@property
def distance(self):
return self._distance / 100
@property
def velocity(self):
return self._velocity * 0.0367
def to_string(self, name):
return (
f'Distance({name}) = {self.distance} [m],'
f' Velocity({name}) = {self.velocity} [km/h],'
f' Signal({name}) = {self.signal_strength} [dB]'
)
class Message(LittleEndianStructure):
_pack_ = 1
_fields_ = [
('sensor_a', SensorData),
('sensor_b', SensorData),
]
def main():
# ...
while True:
now = datetime.now()
save_path = f'/home/pi/serial/{now:%d-%m-%Y}'
log_path = os.path.join(save_path, f'{now:%d-%m-%Y %H:%M}.txt')
picture_filename = f'{now:%H:%M:%S.%f}.jpg'
picture_path = os.path.join(save_path, picture_filename)
os.makedirs(save_path, exist_ok=True)
ser.read_until(b'~~~')
message = Message.from_buffer_copy(ser.read(sizeof(Message)))
signal_trigger_a = message.sensor_a.signal_strength >= signal_trigger
signal_trigger_b = message.sensor_b.signal_strength >= signal_trigger
gpio_trigger = GPIO.input(trigger)
if signal_trigger_a or signal_trigger_b or gpio_trigger:
cam.capture(picture_path)
with open(log_path, 'a', encoding='utf-8') as log_file:
log_file.write(
f'[{now}]:'
f' {message.sensor_a.to_string("a")},'
f' {message.sensor_a.to_string("r")}.'
f' Trigger(a) = {signal_trigger_a},'
f' Trigger(r) = {signal_trigger_b},'
f' Trigger(ETZ) = {gpio_trigger}.'
f' Picture: {picture_filename}\n'
)
else:
print('No triggers detected')
if __name__ == '__main__':
main()
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