def __init__(self):

self.fd = -1

def open(self, devfn = '/dev/usbtmc0'):

self.fd = os.open(devfn, os.O_RDWR)

if self.fd < 0:

return -1

return 0

# read() and write() are low-level method

def read(self):

if self.fd < 0:

return -1

buf = os.read(self.fd, 256) # 256 bytes

return buf

def write(self, buf):

if self.fd < 0:

return -1

n = os.write(self.fd, buf)

return n

# wt310 methods should call read() and write()

def set(self, cmd):

self.write(cmd)

def get(self, cmd):

self.write(cmd)

buf = self.read()

return buf

# send wt310 commands

def readvals(self):

buf = self.get(":NUM:NORM:VAL?\n") # is \n required?

return buf.split(',')

def sample(self):

a = self.readvals()

# default setting. to query, :NUM:NORM:ITEM1? for exampe

# 1: Watt hour, 2: Current, 3: Active Power, 4: Apparent Power

# 5: Reactive Power, 6: Power factor

# note that a's index is the item number minus one

ret = {}

# ret['WH'] = float(a[0])

ret['J'] = float(a[0]) * 3600.0

ret['P'] = float(a[2])

ret['PF'] = float(a[5])

return ret

def start(self):

# set the update interval 100ms (fastest)

self.set(":RATE 100MS")

# set item1 watt-hour

self.set(":NUM:NORM:ITEM1 WH,1")

# start integration

self.set(":INTEG:MODE NORM")

self.set(":INTEG:TIM 2,0,0") # 2 hours

self.set(":INTEG:START")

# ":INTEG:RESET" reset integration

def reset(self):

self.set('*RST') # initialize the settings

self.set(':COMM:REM ON') # set remote mode

def stop(self):

print('')

print('Usage: coolrs_wt310.py [options]')

print('')

print('[options]')

print('')

print('-i int : sampling interval in sec')

print('-o str : output filename')

print('-s str : start the mq producer. str is ip address')

print('--set str : issue command')

print('--get str : query value')

print('')

print('Examples:')

print('$ coolrs_wt310.py -i 0.2 # sample every 0.2 sec')

print('$ coolrs_wt310.py --set=:INTEG:RESET # reset the energy itegration')

print('$ coolrs_wt310.py --get=:NUM:NORM:VAL? # query values')