ANT+ Garmin bike cadence and speed sensor reader

cadence.py

"""
Initialize a basic broadcast slave channel for listening to
an ANT+ HR monitor.

"""

import sys
import time

from ant.core import driver, node, event, message
from ant.core.constants import *

from config import *


def convertSB(raw):
    value = int(raw[1]) << 8
    value += int(raw[0])
    return value


class CadenceListener(event.EventCallback):
    lastEvent = None

    def process(self, msg):
        if isinstance(msg, message.ChannelBroadcastDataMessage):
            page = msg.payload[1] & 0x7F
            if page != 0:
                return

            eventTime = convertSB(msg.payload[5:7])
            if eventTime == self.lastEvent:
                return
            self.lastEvent = eventTime
            revolutions = convertSB(msg.payload[7:9])
            print eventTime, ':', revolutions


NETKEY = '\xB9\xA5\x21\xFB\xBD\x72\xC3\x45'

# Initialize
stick = driver.USB1Driver(SERIAL, log=LOG, debug=DEBUG)
antnode = node.Node(stick)
antnode.start()
antnode.registerEventListener(CadenceListener())

# Set network key
network = node.Network(key=NETKEY, name='N:ANT+')
antnode.setNetworkKey(0, network)

# Get the first unused channel. Returns an instance of the node.Channel class.
channel = antnode.getFreeChannel()

# Initialize it as a receiving channel using our network key
channel.assign(network, CHANNEL_TYPE_TWOWAY_RECEIVE)

# Now set the channel id for pairing with an ANT+ HR monitor
channel.setID(122, 0, 0)

# Listen forever and ever (not really, but for a long time)
channel.searchTimeout = TIMEOUT_NEVER

# We want a ~4.06 Hz transmission period
channel.period = 8102

# And ANT frequency 57
channel.frequency = 57

try:
    # Time to go live
    channel.open()

    print "Listening for events..."
    while True:
        time.sleep(60)
finally:
    # Shutdown channel
    channel.close()
    channel.unassign()

    # Shutdown
    antnode.stop()

config.py

from ant.core import log

# USB1 ANT stick interface. Running `dmesg | tail -n 25` after plugging the
# stick on a USB port should tell you the exact interface.
SERIAL = '/dev/ttyUSB0'

# If set to True, the stick's driver will dump everything it reads/writes
# from/to the stick.
# Some demos depend on this setting being True, so unless you know what you
# are doing, leave it as is.
DEBUG = True

# Set to None to disable logging
LOG = None
#LOG = log.LogWriter()

# ========== DO NOT CHANGE ANYTHING BELOW THIS LINE ==========
#print "Using log file:", LOG.filename
#print ""

speed.py

#!/usr/bin/python

import sys
import time

from ant.core import driver, node, event, message
from ant.core.constants import *

from config import *

NETKEY = '\xB9\xA5\x21\xFB\xBD\x72\xC3\x45'
CIRCUMFERENCE = 2.0

def convertSB(raw):
    value = int(raw[1]) << 8
    value += int(raw[0])
    return value


class SpeedListener(event.EventCallback):
    lastTime = None
    lastRevolutions = None

    def calcSpeed(self, time, revolutions):
        if self.lastTime is None:
            return None

        if time < self.lastTime:
            time += 64 * 1024

        if revolutions < self.lastRevolutions:
            revolutions += 65535

        return (revolutions - self.lastRevolutions) * 1024.0 * CIRCUMFERENCE / (time - self.lastTime)


    def process(self, msg):
        if isinstance(msg, message.ChannelBroadcastDataMessage):
            page = msg.payload[1] & 0x7F
            if page != 0 and page != 5:
                return

            if page == 5:
                stopped = (msg.payload[2] & 1 == 1)
                if stopped:
                    print self.lastRevolutions, 0

            eventTime = convertSB(msg.payload[5:7])
            if eventTime == self.lastTime:
                return

            revolutions = convertSB(msg.payload[7:9])

            speed = self.calcSpeed(eventTime, revolutions)

            print revolutions, speed
            self.lastTime = eventTime
            self.lastRevolutions = revolutions



# Initialize
stick = driver.USB1Driver(SERIAL, log=LOG, debug=DEBUG)
antnode = node.Node(stick)
antnode.start()
antnode.registerEventListener(SpeedListener())

# Set network key
network = node.Network(key=NETKEY, name='N:ANT+')
antnode.setNetworkKey(0, network)

# Get the first unused channel. Returns an instance of the node.Channel class.
channel = antnode.getFreeChannel()

# Initialize it as a receiving channel using our network key
channel.assign(network, CHANNEL_TYPE_TWOWAY_RECEIVE)

# Now set the channel id for pairing with an ANT+ HR monitor
channel.setID(123, 0, 0)

# Listen forever and ever (not really, but for a long time)
channel.searchTimeout = TIMEOUT_NEVER

# We want a ~4.06 Hz transmission period
channel.period = 8118

# And ANT frequency 57
channel.frequency = 57

try:
    # Time to go live
    channel.open()

    print "Listening for events..."
    while True:
        time.sleep(60)
finally:
    # Shutdown channel
    channel.close()
    channel.unassign()

    # Shutdown
    antnode.stop()

Hello. I wonder if speed.py should work for speed and cadence sensor with only corresponding setID and period?