examples: add magnetometer streaming example.

examples/stream_mag.py

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+# usage: python3 stream_mag.py [mac1] [mac2] ... [mac(n)]
+from __future__ import print_function
+from mbientlab.metawear import MetaWear, libmetawear, parse_value
+from mbientlab.metawear.cbindings import *
+from time import sleep
+from threading import Event
+
+import platform
+import sys
+
+if sys.version_info[0] == 2:
+    range = xrange
+
+class State:
+    # init
+    def __init__(self, device):
+        self.device = device
+        self.samples = 0
+        self.magCallback = FnVoid_VoidP_DataP(self.mag_data_handler)
+
+    # mag callback
+    def mag_data_handler(self, ctx, data):
+        print("MAG: %s -> %s" % (self.device.address, parse_value(data)))
+        self.samples+= 1
+
+states = []
+
+# connect
+for i in range(len(sys.argv) - 1):
+    d = MetaWear(sys.argv[i + 1])
+    d.connect()
+    print("Connected to %s over %s" % (d.address, "USB" if d.usb.is_connected else "BLE"))
+    states.append(State(d))
+
+# configure
+for s in states:
+    print("Configuring device")
+    libmetawear.mbl_mw_settings_set_connection_parameters(s.device.board, 7.5, 7.5, 0, 6000)
+    sleep(1.5)
+
+    # setup mag
+    libmetawear.mbl_mw_mag_bmm150_stop(s.device.board)
+    libmetawear.mbl_mw_mag_bmm150_set_preset(s.device.board, MagBmm150Preset.REGULAR)
+
+    # get mag and subscribe
+    mag = libmetawear.mbl_mw_mag_bmm150_get_b_field_data_signal(s.device.board)
+    libmetawear.mbl_mw_datasignal_subscribe(mag, None, s.magCallback)
+
+    # start mag
+    libmetawear.mbl_mw_mag_bmm150_enable_b_field_sampling(s.device.board)
+    libmetawear.mbl_mw_mag_bmm150_start(s.device.board)
+
+# sleep
+sleep(10.0)
+
+# stop
+for s in states:
+    libmetawear.mbl_mw_mag_bmm150_stop(s.device.board)
+    libmetawear.mbl_mw_mag_bmm150_disable_b_field_sampling(s.device.board)
+
+    mag = libmetawear.mbl_mw_mag_bmm150_get_b_field_data_signal(s.device.board)
+    libmetawear.mbl_mw_datasignal_unsubscribe(mag)
+
+    libmetawear.mbl_mw_debug_disconnect(s.device.board)
+
+# recap
+print("Total Samples Received")
+for s in states:
+    print("%s -> %d" % (s.device.address, s.samples))