Magnetometer module

The PyMetaWear implementation of the libmetawear magnetometer module.

It is initialized at the creation of the MetaWearClient client and can then be accessed in the magnetometer attribute of the client.

Data streaming example

If you need a real time stream of sensor data, use the notifications() method on the magnetometer module:

from pymetawear.client import MetaWearClient

c = MetaWearClient('DD:3A:7D:4D:56:F0')

# Set Power preset to low power.
c.magnetometer.set_settings(power_preset='low_power')

def magnetometer_callback(data):
    """Handle a (epoch_time, (x,y,z)) magnetometer tuple."""
        epoch = data[0]
        xyz = data[1]
        print("[{0}] X: {1}, Y: {2}, Z: {3}".format(epoch, *xyz))

# Enable notifications and register a callback for them.
c.magnetometer.notifications(magnetometer_callback)

Logging Example

If you want to log data to the MetaWear board and retrieve it after some time, then use the start_logging(), stop_logging() and download_log() methods:

import os
import json
import time

from pymetawear.client import MetaWearClient
from pymetawear.exceptions import PyMetaWearException, PyMetaWearDownloadTimeout

c = MetaWearClient('DD:3A:7D:4D:56:F0')

# Set Power preset to low power.
c.magnetometer.set_settings(power_preset='low_power')

# Log data for 10 seconds.
c.magnetometer.start_logging()
print("Logging magnetometer data...")

time.sleep(10.0)

c.magnetometer.stop_logging()
print("Finished logging.")

# Download the stored data from the MetaWear board.
print("Downloading data...")
download_done = False
n = 0
data = None
while (not download_done) and n < 3:
    try:
        data = c.magnetometer.download_log()
        download_done = True
    except PyMetaWearDownloadTimeout:
        print("Download of log interrupted. Trying to reconnect...")
        c.disconnect()
        c.connect()
        n += 1
if data is None:
    raise PyMetaWearException("Download of logging data failed.")

print("Disconnecting...")
c.disconnect()

# Save the logged data.
class MetaWearDataEncoder(json.JSONEncoder):
    """JSON Encoder for converting ``mbientlab`` module's CartesianFloat
    class to data tuple ``(x,y,z)``."""
    def default(self, o):
        if isinstance(o, CartesianFloat):
            return o.x, o.y, o.z
        else:
            return super(MetaWearDataEncoder, self).default(o)

data_file = os.path.join(os.getcwd(), "logged_data.json")
print("Saving the data to file: {0}".format(data_file))
with open("logged_data.json", "wt") as f:
    json.dump(data, f, indent=2)

API

Magnetometer module

Created by jboeer <jonas.boeer@kinemic.de> on 2016-09-07

class pymetawear.modules.magnetometer.MagnetometerModule(board, module_id)

MetaWear accelerometer module implementation.

Parameters:

• board (ctypes.c_long) – The MetaWear board pointer value.
• module_id (int) – The module id of this accelerometer component, obtained from libmetawear.
• debug (bool) – If True, module prints out debug information.

module_name

Get module name.

Returns:The name of this module. Return type:str

sensor_name

Get sensor name, if applicable.

Returns:The name of this module. Return type:str or None