Can Linear Acceleration stream faster than 25hz in IMU_Plus mode?

JMoody · October 2019

Board Information

Hardware version [0.3]
Firmware version [1.4.5]
Model number [5]

Host Device information

Device Model [Raspberry Pi 3 B+]
OS Version [Raspbian GNU/Linux 9 (stretch) ]

Description

I would like to stream Linear Acceleration at 100hz, however, I am constantly getting ~ 25Hz or less.
I am using IMU_Plus as my fusion mode. My raw results, and code is listed below

Streaming Raw Acceleration Data has no problem with sending data at 100Hz.

Thank you kindly,

John

Code

from mbientlab.metawear import MetaWear, libmetawear, parse_value
from mbientlab.metawear.cbindings import SensorFusionData, SensorFusionMode, FnVoid_VoidP_DataP
from mbientlab.warble import WarbleException
from threading import Event
import sys
from time import time, sleep, localtime
import os

def timeString():
    result = localtime()
    year = str(result.tm_year)
    month = str(result.tm_mon)
    day = str(result.tm_mday)
    hour = str(result.tm_hour)
    min = str(result.tm_min)
    sec = str(result.tm_sec)
    if int(sec) < 10:
        sec = "0" + str(sec)
    if int(min) < 10:
        min = "0" + str(min)
    if int(hour) < 10:
        hour = "0" + str(hour)
    if int(day) < 10:
        day = "0" + str(day)
    if int(month) < 10:
        month = "0" + str(month)
    time_string = (year + ("_") + month + ("_") + day + '-' + hour + ("_") + min + ("_") + sec)
    return time_string

def create_lin_acc_file():
    ### Create Folder + File for collected data
    path = "./CollectedData/Run_" + timeString()
    access_rights = 0o755
    try:
        os.mkdir(path, access_rights)
    except OSError:
        print("Failed to make %s Directory" % path)
    else:
        print("Successfully created the directory %s " % path)
    file_name_root = path
    file_name_end = str(time()) + ".txt"
    linear_acc_file_name = file_name_root + "/Linear_Acc" + file_name_end
    linear_acc_file = open(linear_acc_file_name, 'a')
    return linear_acc_file

def handle_Linear_Acc(ctx, data):

    linear_acc = parse_value(data)
    time = data.contents.epoch
    xval = linear_acc.x
    yval = linear_acc.y
    zval = linear_acc.z
    #write_string = str(("%d, %d, %d, %d\n" % (time(), xval, yval, zval)))
    write_string = str(str(time()) + ", " + repr(xval) + ", " + repr(yval) + ", " + repr(zval) + '\n')
    linear_acc_file.write(write_string)

    #print(data)
    print("Linear ACC Data : " + write_string)

count = 0
e = Event()

imu_id = 1
addr = 'FA:19:05:96:8B:E4'

if len(sys.argv) > 1:
    addr = "FA:19:05:96:8B:E4"
    imu_id = 2
print(addr)



start_time = None

# Set what type of data we want to collect from the fuser
linear_acc_data_source = SensorFusionData.LINEAR_ACC

max_connect_attempts = 5
linear_acc_file = None


try:
    device = MetaWear(addr)
    device.connect()
    libmetawear.mbl_mw_settings_set_connection_parameters(device.board, 7.5, 7.5, 0, 6000)
    sleep(1.5)
    linear_acc_file = create_lin_acc_file()

except WarbleException as err:
    print('reattempting after warble exception: {}'.format(err))
    exit(1)

try:

    # Set the type of fusion
    libmetawear.mbl_mw_sensor_fusion_clear_enabled_mask(device.board)
    libmetawear.mbl_mw_sensor_fusion_set_mode(device.board, SensorFusionMode.IMU_PLUS)
    libmetawear.mbl_mw_sensor_fusion_write_config(device.board)

    # Set up our Linear ACC and Quaternion processors
    linear_acc_processor = libmetawear.mbl_mw_sensor_fusion_get_data_signal(device.board, linear_acc_data_source)

    # Set up our handlers for our data
    wrapped_handler_linear_acc = FnVoid_VoidP_DataP(handle_Linear_Acc)

    # Subscribe to our data channels
    libmetawear.mbl_mw_datasignal_subscribe(linear_acc_processor, None, wrapped_handler_linear_acc)


    # Enable our data sources
    libmetawear.mbl_mw_sensor_fusion_enable_data(device.board, linear_acc_data_source)


    libmetawear.mbl_mw_sensor_fusion_start(device.board)

    #e.wait()
    # record data for 60 seconds
    sleep(60)

except RuntimeError as err:
    print(err)

finally:
    libmetawear.mbl_mw_sensor_fusion_stop(device.board)
    libmetawear.mbl_mw_sensor_fusion_clear_enabled_mask(device.board)
    libmetawear.mbl_mw_datasignal_unsubscribe(linear_acc_processor)
    libmetawear.mbl_mw_debug_disconnect(device.board)

Raw Results ( snippet)

Laura · October 2019

It is 100Hz if you have nothing else streaming at the same time. Can you confirm this?

Also the default = 100Hz for Sensor fusion, so you should be naturally getting this.

Can you check your BLE? Are you using a dongle?

Can you please run our example scripts for sensor fusion and see if you get closer to 100Hz (don't run your code, run ours instead):
1. Use this as the base: https://github.com/mbientlab/MetaWear-SDK-Python/blob/master/examples/stream_acc.py
2. And replace the signal with a sensor fusion signal: https://github.com/mbientlab/MetaWear-SDK-Cpp/blob/master/test/test_sensor_fusion.py

JMoody · October 2019

Hi Laura,

Thank you for your time.

It is 100Hz if you have nothing else streaming at the same time. Can you confirm this?

I am not currently subscribed to anything else

Can you check your BLE? Are you using a dongle?

No, I am using the onboard radio of the RPi 3B+

Can you please run our example scripts for sensor fusion and see if you get closer to 100Hz (don't run your code, run ours instead):
1. Use this as the base: https://github.com/mbientlab/MetaWear-SDK-Python/blob/master/examples/stream_acc.py
2. And replace the signal with a sensor fusion signal: https://github.com/mbientlab/MetaWear-SDK-Cpp/blob/master/test/test_sensor_fusion.py

Of course, thank you for the suggestion.

Running the following script - https://github.com/mbientlab/MetaWear-SDK-Python/blob/master/examples/stream_acc.py
I am reliably getting ~1230 signals per 30 seconds (41 Hz)

When I replace the signal portion of the code with the configuration available here - https://github.com/mbientlab/MetaWear-SDK-Cpp/blob/master/test/test_sensor_fusion.py
I am fairly consistently receiving ~ 760 signals per 30 seconds (22 Hz)

These results are persistent through reboot of my Linux device(Raspberry Pi 3B+)

Here are two screenshots of the data, as well as the fusion signal code (created using the above links). I am curious if I am perhaps incorrectly implementing the sensor fusion configuration or callback function.

Thank you kindly
- John

Raw Accel

Linear Accel / Sensor Fusion, IMU_Plus Mode

Code

class State:
    def __init__(self, device):
        self.device = device
        self.samples = 0
        self.callback = FnVoid_VoidP_DataP(self.data_handler)

    def data_handler(self, ctx, data):
        print("%s -> %s" % (self.device.address, parse_value(data)))
        self.samples+= 1

states = []
for i in range(len(sys.argv) - 1):
    d = MetaWear(sys.argv[i + 1])
    d.connect()
    print("Connected to " + d.address)
    states.append(State(d))

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)

    libmetawear.mbl_mw_sensor_fusion_clear_enabled_mask(s.device.board)
    signal = libmetawear.mbl_mw_sensor_fusion_get_data_signal(s.device.board, SensorFusionData.LINEAR_ACC)
    libmetawear.mbl_mw_datasignal_subscribe(signal, None, s.callback)

    libmetawear.mbl_mw_sensor_fusion_set_mode(s.device.board, SensorFusionMode.IMU_PLUS)
    libmetawear.mbl_mw_sensor_fusion_enable_data(s.device.board, SensorFusionData.LINEAR_ACC)
    libmetawear.mbl_mw_sensor_fusion_start(s.device.board)

sleep(30.0)

for s in states:
    libmetawear.mbl_mw_sensor_fusion_stop(s.device.board)

    signal = libmetawear.mbl_mw_sensor_fusion_get_data_signal(s.device.board, SensorFusionData.LINEAR_ACC)
    libmetawear.mbl_mw_datasignal_unsubscribe(signal)
    libmetawear.mbl_mw_debug_disconnect(s.device.board)

print("Total Samples Received")
for s in states:
    print("%s -> %d" % (s.device.address, s.samples))

JMoody · October 2019

Oh Dear.

I reset the board using libmetawear.mbl_mw_debug_reset(s.device.board).

Now, the linear accel data is reading much faster (100Hz!), however, all of the readings are zero. I will have to go back and ensure I am enabling the sensor fusion correctly.

Thank you for your assistance Laura.

Laura · October 2019

Great news @JMoody.
Perhaps the sensor was doing other things internally that were eating up bandwidth?
Glad it worked out

Onikii · February 2020

Hi @JMoody.
I tried using your code but I found a problem with the value are always 0 all along. Help me please.

Laura · February 2020

Please follow the rules on posts: https://mbientlab.com/community/discussion/3167/how-to-report-an-issue#latest

Onikii · February 2020

@Laura said:
Please follow the rules on posts: https://mbientlab.com/community/discussion/3167/how-to-report-an-issue#latest

Oh I see, Sorry for the bad manners.

Can Linear Acceleration stream faster than 25hz in IMU_Plus mode?

Board Information

Host Device information

Description

Code

Raw Results ( snippet)

Comments

Raw Accel

Linear Accel / Sensor Fusion, IMU_Plus Mode

Code