For this project, I have been making a vibration measurement device that plots high speed vibrations that are controlled by a motor. Here is the code below:
# Import the modules
from __future__ import division
import spidev, datetime, time
from sys import exit
import RPi.GPIO as GPIO
# Setup SPI
spi = spidev.SpiDev()
spi.open(0, 0)
spi.mode = 3
# Constants
accres, accrate = 1, 15
# Set GPIO chip select pins
GPIO.setwarnings(False)
GPIO.setmode(GPIO.BCM)
cs1, cs2, motor = 23, 24, 18
GPIO.setup(cs1, GPIO.OUT)
GPIO.setup(cs2, GPIO.OUT)
GPIO.setup(motor, GPIO.OUT)
# Note: the duty cycle goes from 0.0 to 100.0, with 100.0 being no motor movement,
# and 0.0 being the maximum motor speed.
motor_output = GPIO.PWM(motor, 60)
# Initialize the ADXL345
def initadxl345():
# Set data rate (accrate=15 -> 3200 Hz, 14=1600 Hz, 13=800 Hz, 12=400 Hz, 11=200 Hz, 10=100 Hz etc.)
spi.xfer2([44, accrate])
# Enable full range (10 bits resolution) and +/- 16g 4 LSB
spi.xfer2([49, accres])
# Read the first ADXL x-y-z axes
def readadxl345_1():
# Chip select pin ensures that the first sensor is being read by grounding its pin
GPIO.output(cs1, 0)
GPIO.output(cs2 ,1)
rx = spi.xfer2([242, 0, 0, 0, 0, 0, 0])
out = [rx[1] | (rx[2] << 8), rx[3] | (rx[4] << 8), rx[5] | (rx[6] << 8)]
# Format x-axis
if (out[0] & (1 << 16 - 1 )):
out[0] = out[0] - (1 << 16)
# Format y-axis
if (out[1] & (1 << 16 - 1 )):
out[1] = out[1] - (1<<16)
# Format z-axis
if (out[2] & (1 << 16 - 1 )):
out[2] = out[2] - (1 << 16)
# Return human readable values
return out
# Read the second ADXL x-y-z axes
def readadxl345_2():
# Chip select pin ensures that the first sensor is being read by grounding its pin
GPIO.output(cs1, 1)
GPIO.output(cs2 ,0)
rx = spi.xfer2([242, 0, 0, 0, 0, 0, 0])
out = [rx[1] | (rx[2] << 8), rx[3] | (rx[4] << 8), rx[5] | (rx[6] << 8)]
# Format x-axis
if (out[0] & (1 << 16 - 1 )):
out[0] = out[0] - (1 << 16)
# Format y-axis
if (out[1] & (1 << 16 - 1 )):
out[1] = out[1] - (1<<16)
# Format z-axis
if (out[2] & (1 << 16 - 1 )):
out[2] = out[2] - (1 << 16)
# Return human readable values
return out
print("Vibration Reader Initializing...")
time.sleep(1)
print(GPIO.RPI_INFO)
time.sleep(1)
response = input("Proceed measurements? [Y, n] ")
if response == "Y" or "y":
filename = input("Filename: ")
pwm_speed = float(input("Motor PWM value: "))
# Initialize the ADXL345 accelerometer
print("Initializing ADXL345s...")
initadxl345()
motor_output.start(pwm_speed)
print("Motor is up and running at {}".format(pwm_speed))
time.sleep(1)
timeout = 0.0003125 / 2 # timeout=1/samplerate=>not sufficient measurements. Half the time is sufficient (don't know why!)
timetosend = 1
while True:
with open('/proc/uptime', 'r') as f: # get uptime
uptime_start = float(f.readline().split()[0])
uptime_last = uptime_start
active_file_first = filename + '.csv'
file = open('/var/log/sensor/' + active_file_first, 'w')
while uptime_last < uptime_start + timetosend:
time1 = str(datetime.datetime.now().strftime('%S.%f'))
sensor1 = readadxl345_1()
sensor2 = readadxl345_2()
file.write(str(sensor1[0]) + ',' + str(sensor1[1]) + ',' + str(sensor1[2]) + ',' + str(sensor2[0]) + ',' + str(sensor2[1]) + ',' + str(sensor2[2]) + ',' + time1 + '\n')
# Print data every "timeout" second
elapsed = time.process_time()
current = 0
while(current < timeout):
current = time.process_time() - elapsed
motor_output.stop
print("Motor shutting off and cleaning up GPIO.")
GPIO.cleanup()
elif response == "N" or "n":
print("Quitting...")
time.sleep(1)
quit()
From this I get into trouble. The issue is that once I do choose to proceed, the print statement Motor is up and running at 100.0 displays and nothing happens until I press a random key on the keyboard in which is says
Traceback (most recent call last):
File "accelerometer.py", line 116, in <module>
current = time.process_time() - elapsed
KeyboardInterrupt
Its as if the code following that print statement didn't even exist, or the interpreter just ignored it completely. Does anyone have a coherent explanation of these problems?
Let's take a step back and think about what this block of code is doing:
while True:
### Block 1 ###
with open('/proc/uptime', 'r') as f: # get uptime
uptime_start = float(f.readline().split()[0])
uptime_last = uptime_start
active_file_first = filename + '.csv'
file = open('/var/log/sensor/' + active_file_first, 'w')
### Block 2 ###
while uptime_last < uptime_start + timetosend:
time1 = str(datetime.datetime.now().strftime('%S.%f'))
sensor1 = readadxl345_1()
sensor2 = readadxl345_2()
file.write(str(sensor1[0]) + ',' + str(sensor1[1]) + ',' + str(sensor1[2]) + ',' + str(sensor2[0]) + ',' + str(sensor2[1]) + ',' + str(sensor2[2]) + ',' + time1 + '\n')
# Print data every "timeout" second
elapsed = time.process_time()
current = 0
### Block 3 ###
while(current < timeout):
current = time.process_time() - elapsed
Block 1 checks an uptime file, reads the time and then opens a file. However, if this uptime_start variable never changes, then we can just set it once outside of (and instead of) the top while loop. Block 2 then checks uptime_last < uptime_start + x, but in the previous few lines, you've defined uptime_last = uptime_start. This means that for as long as the timetosend is not negative, this loop will execute infinitely unless an internal break condition is met. Block 2 writes sensor data to file. Block 3 does a time calculation until a condition is met, but doesn't really do anything with this information.
My guess as to what could be a good answer is this:
### Block 1 ###
with open('/proc/uptime', 'r') as f: # get uptime
uptime_start = float(f.readline().split()[0])
file = open('/var/log/sensor/' + filename + '.csv', 'w')
time_elapsed = 0
time_start = time.process_time()
### Block 2 ###
while time_elapsed < uptime_start:
time1 = str(datetime.datetime.now().strftime('%S.%f'))
sensor1 = readadxl345_1()
sensor2 = readadxl345_2()
file.write(str(sensor1[0]) + ',' + str(sensor1[1]) + ',' + str(sensor1[2]) + ',' + str(sensor2[0]) + ',' + str(sensor2[1]) + ',' + str(sensor2[2]) + ',' + time1 + '\n')
time_elapsed = time.process_time() - time_start