pressure_gauge.py

 #!/usr/bin/env python

import time, serial

"""
This is the Pressure object which reads pressure 
measurements from the 358 Micro-Ion Controller.
"""
class Pressure(object):
    
    timeout = 5   # At most 5 second read wait necessary.
    
    def __init__(self, port='/dev/tty.USA19H1463P1.1'):
        self.port = port
        self.start_serial(self.port)

    #Open a port for serial communication. 
    def start_serial(self, port):
        # Configure the serial connections. 
        # These are specific to the 358 Micro-Ion Controller
        # This device is configurable, but these are default (except for BAUD). 
        # Currently set to send out a message every 5 seconds, non interactively.
        # Could set to "interactive" mode with a switch inside, but no need.
        try:
            self.ser = serial.Serial(
                    port=port,
                    baudrate=9600,
                    parity=serial.PARITY_NONE,
                    bytesize=serial.EIGHTBITS,
                    stopbits=serial.STOPBITS_ONE,
                    timeout=5
            )

            # Force these to true:
            self.ser.setDsrDtr(True)
            self.ser.setRtsCts(True)
            
        except:
            print("Something went wrong...")
        
        
    # Unused
    def write(self, command):
        self.ser.write(command + '\r\n')
         
         
    def close_serial(self):
        self.ser.close()


    def read(self):
            out = []
            terminated = False
            # Flush input (constantly sending messages)
            while self.ser.inWaiting() > 0: str(self.ser.read(1))
            # Read newest message when buffer clear (5 sec delay)
            start = time.time()
            while (self.ser.inWaiting() > 0 or not terminated) and time.time() - start < self.timeout:
                data = str(self.ser.read(1))
                if data == '\r':
                    terminated = True
                else:
                    out.append(data)
            
            if out != '':
                return ' '.join(out)[:-1]  # Drop the \n
            else:
                return ''

    # Unused
    def write_and_read(self, command):
        self.write(command)
        return self.read()
        
    # Checks if pressure unit sends anything. Try twice, just in case.
    def check_ready(self):
        test = self.read()
        if len(test) != 0:
            return True
        else:
            test = self.read()
            if len(test) != 0:
                return True
            else:
                return False
                
    def getReadings(self):
        readings = self.read().replace(' ', '').split(',')
        return [float(r) for r in readings]
        
if __name__ == '__main__':
    
    pressure = Pressure()
    measurements = pressure.read().replace(' ', '').split(',')
    for i in measurements:
        print(i)