I have a wireless sensor node that transmits wirelessly to a receiver connected to my computer. I use this command to see the data in real time
sudo stdbuf -o0 ./pip_sense.v2 l l | stdbuf -o0 grep -P "TX:03(376|004)
I am new to Python, but I was able to develop a piece of code as show below to capture the stdout and takes frames from a camera connected to the same computer. That is when a packet (data) is received, at that timestamp, a frame will be captured.
It is working fine, except the fact that its running slow. I am running my sensor at a rate of 10 Hz (transmitting every 0.1 sec.) but the code does what is required at a slower rate. I know that is because I am using cv2.imwrite() (I commented out this part and that helped in reducing the delay). But also, as discussed in this post and its said (as I understand) that using shell=True can invoke extra shell process and thus increase the delay.
Also, looking at this, Popen() seems to be causing delays as well. A solution is proposed in the second link, but I do not really understand how to modify it to work for me.
#!/usr/bin/env python
from subprocess import Popen, PIPE
import time
import sys
import cv2
import os
import csv
import argparse
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
from collections import OrderedDict
from datetime import datetime
PIP_CMD = 'sudo stdbuf -o0 ./pip_sense.v2 l l | stdbuf -o0 grep -P "TX:03(376|004)"'
def run(command):
process = Popen(command, stdout=PIPE, shell=True)
while True:
line = process.stdout.readline().rstrip()
if not line:
break
yield line
print ('Starting...')
def createFolder(directory):
try:
if not os.path.exists(directory):
os.makedirs(directory)
except OSError:
print ('Error: Creating directory. ' + directory)
createFolder('/home/piptag/pip-test/capture_webcam/EXPERIMENTS')
file1 = open('/home/piptag/pip-test/capture_webcam/EXPERIMENTS/3376.txt','w')
file1.write("Time Stamp \t TX ID \t RSSI \tSEQ NO \tCAP \tX-Axis \tY-Axis \tZ-Axis \t X \t Y \t Z \n") # Header line
file1.write("-------------------------------------------------------------------------------------------------------------------------------------\n")
file2 = open('/home/piptag/pip-test/capture_webcam/EXPERIMENTS/3004.txt','w')
file2.write("Time Stamp \t TX ID \t RSSI \tSEQ NO \tX-Axis \tY-Axis \tZ-Axis \t X \t Y \t Z \n") # Header line
file2.write("-------------------------------------------------------------------------------------------------------------------------------------\n")
dirname = "/home/piptag/pip-test/capture_webcam/EXPERIMENTS/"
def save_webcam(dirname):
cam = cv2.VideoCapture(-1) # was getting error (V4L: can't open camera by index 0), thus changes it to -1
jpg_quality = 75
frame_number = 0
if cam.isOpened():
ret_val, img = cam.read()
else:
ret_val = False
timestamp = int(TS)
path = dirname + str(tx) + str("-") + str(timestamp) + ".jpg"
cv2.imwrite(path, img, [int(cv2.IMWRITE_JPEG_QUALITY), jpg_quality])
frame_number = frame_number + 1
##this is the end of the camera program
def twos_comp(val, bits):
"""compute the 2's compliment of int value val"""
if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
val = val - (1 << bits) # compute negative value
return val # return positive value as is
#########################################MAIN###################################
if __name__ == "__main__":
for line in run(PIP_CMD):
raw_data = line.split('\t')
if len(raw_data) > 1:
TS = raw_data[0][3:]
tx = raw_data[3].split(':')[-1]
rssi = float(raw_data[4][5:])
crc_ok = True if (raw_data[5] != b'BAD CRC') else False
no_drop = True if (raw_data[1] == b'Drop:0') else False
# If CRC check is ok and no drop, process the packet
if crc_ok and no_drop:
data = raw_data[-1].split(':')[-1].split()
cat = ""
for i in data:
cat += str(i)
if tx == '03376':
save_webcam(dirname)
print data
CapStatus=data[1]
if CapStatus == '50':
Cap='0'
elif CapStatus == '51':
Cap='1'
SEQNO1=str(int((data[2]),16))
x_axis1=data[3]+data[4]
y_axis1=data[5]+data[6]
z_axis1=data[7]+data[8]
TX1=tx
x1 = twos_comp(int(x_axis1,16), 16) * 0.0039 #* 9.80665 #the value is multiplied by 0.004 as the ADXL345 reports data as 4mg per 1lsb
y1 = twos_comp(int(y_axis1,16), 16) * 0.0039 #* 9.80665 #the value is multiplied by 0.004 as the ADXL345 reports data as 4mg per 1lsb
z1 = twos_comp(int(z_axis1,16), 16) * 0.0039 #* 9.80665 #the value is multiplied by 0.004 as the ADXL345 reports data as 4mg per 1lsb
st1 = str(TS) + "\t "+ "{:<5}".format(str (TX1)) + "\t" + "{:<10}".format(str (rssi)) + "{:<5}".format(SEQNO1) + "\t" + "{:<5}".format(str (Cap)) + "\t" + "{:<5}".format(str (x_axis1)) + "\t" + "{:<5}".format(str (y_axis1)) + "\t"+ "{:<5}".format(str(z_axis1)) + "\t" + "{:<5}".format(str(x1)) + "\t" + "{:<5}".format(str(y1)) + "\t" + "{:<5}".format(str(z1)) +"\n"
file1.write(st1)
elif tx == '03004':
save_webcam(dirname)
print data
SEQNO2=str(int((data[1]),16))
x_axis2=data[2]+data[3]
y_axis2=data[4]+data[5]
z_axis2=data[6]+data[7]
TX2=tx
x2 = twos_comp(int(x_axis2,16), 16) * 0.0039 #* 9.80665 #the value is multiplied by 0.004 as the ADXL345 reports dataas 4mg per 1lsb
y2 = twos_comp(int(y_axis2,16), 16) * 0.0039 #* 9.80665 #the value is multiplied by 0.004 as the ADXL345 reports data as 4mg per 1lsb
z2 = twos_comp(int(z_axis2,16), 16) * 0.0039 #* 9.80665 #the value is multiplied by 0.004 as the ADXL345 reports data as 4mg per 1lsb
st2 = str(TS) + "\t "+ "{:<5}".format(str (TX2)) +"\t "+ "{:<10}".format(str (rssi)) + "{:<5}".format(SEQNO2) + "\t" + "{:<5}".format(str (x_axis2)) + "\t"+ "{:<5}".format(str (y_axis2)) + "\t"+ "{:<5}".format(str(z_axis2))+ "\t"+"{:<5}".format(str(x2)) + "\t" + "{:<5}".format(str(y2))+ "\t"+ "{:<5}".format(str(z2)) +"\n"
file2.write(st2)
file1.close()
file2.close()
I appreciate any help
Thank you
