So here is how I’ve tackled this (your mileage may vary)
On the Arduino Side:
(I send a CRLF terminated line starting with a data type descriptor: in this case “SNSR” for sensor data)
void Send_Sensors() {
Serial.print(“SNSR,”);
Serial.print( now); Serial.print(",");
Serial.print(motion); Serial.print(",");
Serial.print(AccScaled.XAxis); Serial.print(",");
Serial.print(AccScaled.YAxis); Serial.print(",");
Serial.print(AccScaled.ZAxis); Serial.print(",");
Serial.print(CurrentHeading); Serial.print(",");
Serial.print(DirectAhead); Serial.print(","); Serial.print(DirectBehind); Serial.print(",");
Serial.print(DirectRight); Serial.print(","); Serial.print(DirectLeft); Serial.print(",");
Serial.print(FrontRight); Serial.print(","); Serial.print(FrontLeft); Serial.print(",");
Serial.print(Temperature); Serial.print(","); Serial.print(Pressure); Serial.print(",");
Serial.print(Altitude); Serial.print(","); Serial.println(batvolt);
}
On the Raspberry Pi Python Side:
(Caveat: this is just a snippet from my code… it may not function as is:)
I import Serial
I declare a function to read and parse a line from Serial
I set up the serial port and open it.
I then wait for incoming data in my main loop. If the first field matches what I’m looking for, I update my variables.
#! /usr/bin/python
#
import serial
########################################################################
# Global Variables - Yes I know these are bad…
accel_x = 0.0
accel_y = 0.0
accel_z = 0.0
heading = 0.0
directahead = 0.0
directbehind = 0.0
directleft = 0.0
directright = 0.0
voltage = 0
ready=0 # ready to send command to arduino
timeout = 0 # To avoid infinite wait state, we will count 100 loops and assume failure
line = None # Holds current response from Arduino Serial
line_len = 0 # number of items in “line”
##########################################################################
# Declare functions
def get_arduino_response():
global line
global line_len
if (arduino.inWaiting() > 0): # Number of characters in arduino buffer
line = arduino.readline()
line = line.split(",")
line_len = len(line)
print 'Receiving: line[0]= ’ , line, 'Num Items= ', line_len, ‘timeout= ‘, timeout
##########################################################################
# Set up serial port to Arduino
arduino = serial.Serial(’/dev/ttyACM0’, 115200, timeout = 10)
arduino.open()
time.sleep(10) # Time for Arduino to reset and settle
arduino.flushInput()
##########################################################################
# Main Loop
try:
running = True
while 1: # Continuous loop
# os.system(‘clear’)
stamp = time.time()
get_next_command() # find the next available command to process
get_arduino_response() # If data available from arduino, retrieve into “line”
if line[0] == “SNSR” and line_len == 13: # Ensure entire line came through
ardtime = line[1]
motion = line[2]
accel_x = float(line[3])
accel_y = float(line[4])
accel_z = float(line[5])
heading = float(line[6])
directahead = float(line[7])
directbehind = float(line[8])
directleft = float(line[9])
directright = float(line[10])
voltage = line[11]
UID = line[12]
UID = UID.strip()
print 'line ’ , ardtime, accel_x, accel_y, accel_z, heading ,‘done’
except (KeyboardInterrupt, SystemExit): #when you press ctrl+c
print “\nKilling Thread…”
db.close()
print “Done.\nExiting.”
