working with 2 MetaWear boards simultaneously using python, Linux and Bluetooth

mohamed167

as the title says i am using the provided Python code and the C++ APIs to communicate with 2 MetaWear CPro at the same time

i was able to comunicate with the two boards and get the ACC data in different CSV files my problem now is with the data rate it self

i have set both boards to work with datarate of 100 but what is strange is that when i receive the data of both boards

the first sensor data are received with data rate of 14 Hz

while the second sensor data are received with data rate of 100

i tried this with different combinations of data rate and the same results always happen where the first sensor works with data rate of 14 Hz and the second sensor works with the data rate i set both to work with

Eric

Can you post the full python code you are currently running along with the firmware revision the boards are currently running?

mohamed167

i am using metawear CPro boards with firmware 1.2.2
i use the example code for handling the ACC sensor but with multithreading to communicate with different metawear boards

here is the code i am using

mohamed167

# -*- coding: utf-8 -*-
"""
Created by hbldh
Created on 2016-04-02
"""

from __future__ import division
from __future__ import print_function
from __future__ import absolute_import
import time, datetime, csv, pygatt, signal, threading
from datetime import datetime
from pymetawear.client import MetaWearClient

address_1 = 'EF:D3:4F:FF:C8:D4'
address_2 = 'DE:0B:16:99:D6:8A'

print("Connect to {0}...".format(address_1))
c_1 = MetaWearClient(str(address_1), timeout=10.0, debug=False)
print("New client created: {0}".format(c_1))
print("Connect to {0}...".format(address_2))
c_2 = MetaWearClient(str(address_2), timeout=10.0, debug=False)
print("New client created: {0}".format(c_2))

def handler(signum, frame):
print ("force disconnect")
c_1.accelerometer.notifications(None)
c_2.accelerometer.notifications(None)
time.sleep(5.0)
c_1.disconnect()
c_2.disconnect()

signal.signal(signal.SIGTSTP, handler)

def acc_callback1(data):

now = datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S.%f')
print("Client_1, X: {1}, Y: {2}, Z: {3}".format(data[0], *data[1]))

datastr = ("{1},{2},{3}".format(data[0], *data[1]))
data="".join(datastr)
datarow=now+","+data

with open('accthread1.csv', 'a') as csvfile:
writer = csv.writer(csvfile, delimiter=' ',
escapechar=' ', quoting=csv.QUOTE_NONE)
writer.writerow([datarow])

def acc_callback2(data):

now = datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S.%f')
print("Client_2, X: {1}, Y: {2}, Z: {3}".format(data[0], *data[1]))

datastr = ("{1},{2},{3}".format(data[0], *data[1]))
data="".join(datastr)
datarow=now+","+data

with open('accthread2.csv', 'a') as csvfile:
writer = csv.writer(csvfile, delimiter=' ',
escapechar=' ', quoting=csv.QUOTE_NONE)
writer.writerow([datarow])

class BleThread (threading.Thread):
def __init__(self, threadID, name, client):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.client = client
def run(self):
if self.client == 1 :
print("Write sensor 1 settings...")
c_1.accelerometer.set_settings(data_rate=100, data_range=16.0)
print("getting sensor 1 data")
c_1.accelerometer.high_frequency_stream = False
c_1.accelerometer.notifications(acc_callback1)
if self.client == 2 :
print("Write sensor 2 settings...")
c_2.accelerometer.set_settings(data_rate=100, data_range=16.0)
print("getting sensor 2 data")
c_2.accelerometer.high_frequency_stream = False
c_2.accelerometer.notifications(acc_callback2)

thread1 = BleThread(1, "sensor_1", 1)
thread2 = BleThread(2, "Sensor_2", 2)

thread1.start()
thread2.start()

while 1:
time.sleep(20.0)

Eric

You need to enable high frequency streaming to stream from multiple devices.  See my post from your other thread.

http://community.mbientlab.com/discussion/comment/4169/#Comment_4169

mohamed167

thanks for your reply

i have updated the firm ware on my 3 MetaWear Boards and enabled high frequency stream

there was improvement of the data rate of the first 2 boards but the same problem exists 

what is mean is that i set the data rate to 100 Hz in all boards and start having data from the 3 MetaWear boards but the first 2 boards i receive with data rate 40 and 42 Hz while the third board i receive data rate of 100 Hz

even when i decrease the data rate to 50 Hz 2 boards have data rate of 40 Hz and the 3rd board have a 50 Hz data rate

and what i need is to receive data from the three boards with rate of 100 Hz

any help will be appreciated thanks again.

Eric

Reduce the max connection interval to 7.5ms.  You might have to reconnect to the boards to have the connection intervals renegotiated, not sure if the Linux ble stack supports live changes.

http://community.mbientlab.com/discussion/comment/3825/#Comment_3825

mohamed167

thanks alot @Eric it worked for me finally and with out the need to reconnect

this is the command i use as mentioned in the post you added

libmetawear.mbl_mw_settings_set_connection_parameters(c_1.board, 7.5, 7.5, 0, 6000)