spacetime.py

import serial
import time
from timeutil import *

CRLF = '\r\n'
  
class SerialMsg:
  def __init__(self, msgtype, msgval):
    self.type = msgtype
    self.val = msgval

class SpaceTime:
  #See Serial protocol for communicating with SpaceTime at:
  #https://github.com/BruceFletcher/SpaceTime/blob/master/sw/serial.c
  BAUD = 57600
  
  def __init__(self, serialDeviceName = '/dev/ttyAMA0'):
    self.serial = serial.Serial(serialDeviceName, self.BAUD, timeout=1)
  
  def ClearSerial(self):
    #Clear the local Serial buffers as well as SpaceTime's buffer
    
    #Send a newline to ensure SpaceTime buffer is emptied
    self.serial.write(CRLF)
    self.serial.flush()      #Ensure the CRLF is sent
    time.sleep(0.25)         #Give SpaceTime some time to respond
    self.serial.flushOutput()#Discard any data in the out buffer
    self.serial.flushInput() #Discard any data in the input buffer
    
  def CanRead(self):
    #Checks whether there is serial data waiting to be read from SpaceTime
    return self.serial.inWaiting() > 0
    
  def IsConnected(self, timeout = 10, writedelay = 0.25):
    #Queries SpaceTime over Serial connection and waits for proper acknowledgement.
    #Will return within 'timeout' seconds, and queries are sent every 'writedelay' seconds.
    #Returns True if SpaceTime acknowledges, and False if timeout exceeded.
    
    start_time = time.time()
    while 1:
      #'AT' should trigger SpaceTime to respond with 'OK'
      self.serial.write('AT' + CRLF)
      while self.CanRead():
        #Check if received value is expected acknowledgement from SpaceTime
        if self.serial.readline() == 'OK' + CRLF:
          #We have verified the serial connection!
          self.ClearSerial()
          return True;
      #Return false if time exceeded
      if time.time() - start_time > timeout:
        return False;
      #Add small delay between writes in case SpaceTime is offline or busy
      time.sleep(writedelay)
      
  def Read(self):
    #Returns a SerialMsg with type as 'Current' or 'Closing' time, and
    #val as a struct_time or None if time is cleared. Other types:
    # AmbiguousTime (for time queries that reply without clock name. Similar to above.)
    # OK (for 'OK' response)
    # AT Command Echo (for our commands that were echoed back by SpaceTime)
    # Boot (for the message that SpaceTime sends upon startup)
    # Unknown (for any other serial message)
    #For all of these, val = the full message received
    
    data = self.serial.readline()
    if data.startswith('OK'):
      return SerialMsg('OK', data)
    elif data.startswith('AT'):
      #SpaceTime echoes all AT Commands that we sent to it
      return SerialMsg('Echo', data)
    elif data.startswith('Closing time: ') or data.startswith('Current time: '):
      msgtype = data[:7]    #Both 'Current' and 'Closing' are 7 chars long
      timeval = None
      if not data.endswith('Not set' + CRLF):
        timeval = data[14:-2] #Refers to all the text after 'Closing time: ' and before \r\n
      return SerialMsg(msgtype, timeval)
      
    #SpaceTime says this on boot/reset
    elif data == 'SpaceTime, yay!' + CRLF:
      return SerialMsg('Boot', data)
    #If we query SpaceTime for a particular clock's time, it returns with
    #either 'Not set' or an 'HH:MM:SS' time, but no label specifying which
    #clock it refers to.
    elif data.startswith('Not set'):
      return SerialMsg('AmbiguousTime', None)
    else:
      if IsTimeStr(data[0:-2]): #[0:-2] removes the \r\n
        return SerialMsg('AmbiguousTime', data[0:-2])
      return SerialMsg('Unknown', data)
      
  def SerialCommand(self, cmd):
    #Sends serial command to SpaceTime
    self.serial.write(cmd + CRLF)
  
  def SetTime(self, clockID, timestruct):
    #ATST<n>=04:23:11
    #Triggers SpaceTime to set selected clock's time and return it, ex:
    # Current time: hh:mm:ss\r\n
    # OK\r\n
    t = TimeToStr(timestruct)
    self.SerialCommand('ATST' + str(clockID) + '=' + t)
  
  def GetTime(self, clockID):
    #ATST<n>?
    #Triggers SpaceTime to return selected clock's time, ex:
    # Current time: hh:mm:ss\r\n
    # OK\r\n
    self.SerialCommand('ATST' + str(clockID) + '?')
  
  def ClearTime(self, clockID):
    #ATST<n>=X
    #Triggers SpaceTime to clear clock's time, ex:
    # Closing time: Not set\r\n
    # OK\r\n
    self.SerialCommand('ATST' + str(clockID) + '=X')