Time & Location Requests
Once the Notecard is connected to a cell network or GPS, there are a number of requests available for obtaining the time, location, and using the onboard GPS module for location tracking.
Obtaining the Current Time and Date
To obtain the current time, expressed as a Unix epoch value, use the
card.time request. Note: Upon power-up, the Notecard must complete a
sync to Notehub in order to obtain time and location data.
Sending this request yields a response that includes the current UNIX Epoch
time, local time zone, minutes East of GMT, latitude (lat), longitude
(lon), and country.
{
"time": 1598478570,
"area": "Beverly, MA",
"zone": "CDT,America/New York",
"minutes": -300,
"lat": 42.577600,
"lon": -70.871340,
"country": "US",
}
noteTower Location vs. Notecard Location
It's important to note that the location values returned by a card.time
request correspond to the cellular tower to which the Notecard
last connected. This may differ widely from the physical location of the
Notecard. For greater accuracy of location, you'll want to use
card.location APIs described below.
Until the Notecard has connected to a cellular network, it does not know the
time. In those cases, card.location requests respond with a zone value of
UTC,Unknown.
{"zone":"UTC,Unknown"}Using Cell Tower & Wi-Fi Triangulation
For improved location accuracy without using GPS, the Notecard provides optional triangulation capabilities that can gather information about surrounding cell towers and/or local Wi-Fi access points to ascertain a location upon each new Notehub session.
Due to the low-power nature of the Notecard, triangulation-derived location data
is only available if the Notecard has detected motion with its onboard
accelerometer (unless overridden by card.triangulate arguments).
Cell tower triangulation is only available with the Cellular Notecard and should be used sparingly if your device is battery-powered, as it can add 1-2 minutes of connection time whenever the Notecard powers on the cellular modem to establish a connection with Notehub.
Wi-Fi triangulation is available with both the Cellular and Wi-Fi Notecards. Unlike cell tower triangulation, it adds only 1-2 seconds of processing time, uses minimal power, can be nearly as accurate as a GPS-derived location, but does require additional configuration (see below).
warningWi-Fi triangulation is an experimental, technical preview feature that is free for use today, but may use Consumption Credits in the future. Blues reserves the right to rate limit excessive Wi-Fi triangulation requests at our discretion.
Enabling Triangulation
To enable triangulation, use the card.triangulate request with the mode
argument set to wifi, cell, or both, separated by a comma:
This request will return an object confirming that triangulation is enabled with
the mode provided, and a motion field indicating the last time device
movement was detected.
{ "mode": "wifi,cell", "motion": 1606761044 }
Depending on your requirements, you may also need to change the frequency at
which triangulation data is processed on Notehub. The default is "Daily", which
means at most triangulation data will be processed once per day. This option is
available in the Settings of your Notehub project and also updatable as the
_tri_mins environment variable:
noteA card.triangulate request does not itself perform triangulate with the
Notecard. Rather, it gathers cell tower and/or Wi-Fi access point data that
Notehub uses to perform device triangulation.
In addition, this feature does not affect the location data returned by a
card.location request, but is intended to increase the accuracy of location
data sent from Notehub to any
Routes defined in a
project. See
Viewing Triangulation Location Data in Notehub
below to understand where triangulation-based location data appears in Notehub
events.
Providing Wi-Fi Information to the Notecard
If your host has an onboard Wi-Fi module, you can perform a manual
access point scan and send this information to the Cellular Notecard using the
text argument. Sending this data to the Cellular Notecard is required to
enable Wi-Fi triangulation, while the Wi-Fi Notecard has triangulation
enabled by default.
The format of the text field must be a newline-terminated list of Wi-Fi access
points that follows a pattern similar to the
ESP32's AT+CWLAP
command output.
This request will return an object with the current triangulation
configuration parameters, and a length field indicating the size of the
text buffer provided in the request.
{ "usb": true, "mode": "wifi", "length": 398, "on": true, "time": 1606770857, "motion": 1606770581 }
noteUse the Notecard Auxiliary Wi-Fi Arduino library for an easier way of programmatically pulling a list of Wi-Fi access points with your Wi-Fi enabled host MCU and sending them to the Notecard.
Using Triangulation with the Wi-Fi Notecard
The Wi-Fi Notecard supports Wi-Fi triangulation only and is enabled by default, with no end-user configuration required. Every event in Notehub sent by a Wi-Fi Notecard will have triangulation location data appended.
Viewing Triangulation Location Data in Notehub
Enabling cell tower or Wi-Fi triangulation does not affect the location data
returned by a card.location request (which is reserved solely for GPS location
data). However, when triangulation is enabled, additional triangulation-derived
fields with lat/lon coordinates will appear in Notehub events, prepended with
tri_, and may be routed. For example:
"tri_when": 1656011112, "tri_lat": 43.07113895, "tri_lon": -89.43272533, "tri_location": "Shorewood Hills WI", "tri_country": "US", "tri_timezone": "America/Chicago", "tri_points": 16,
Configuring USB Power and Motion-based Triangulation
The card.triangulate request provides options for configuring the Notecard
based on its power state and movement. Set the usb argument to true
to instruct the Notecard to only perform triangulation when connected to USB
power, and set on to true if you want the Notecard to triangulate even when
the device has not moved. Both flags require the set argument in order to
take effect.
This request will return an object with the current triangulation
configuration parameters, a motion field indicating the time of the last
device movement, and time field indicating the time of the last triangulation
scan.
{ "mode": "wifi,cell", "usb": true, "on": true, "time": 1606758961, "motion": 1606761044 }
Disabling Triangulation
To turn triangulation off, set the mode argument to -:
This request will return an object with no mode argument, indicating that
triangulation is disabled. The motion and time fields may still be present
after triangulation is disabled.
{ "motion": 1606761044 }
Working with GPS on the Notecard
The Notecard includes an onboard GPS module that can be used for location
tracking, when paired with an appropriate antenna. To conserve power, the GPS
module on the Notecard is off, by default. You can confirm this with the
card.location request:
Which will return the following:
{
"status": "GPS is off {gps-inactive}",
"mode": "off"
}When using GPS mode, you'll want to decide whether your application should enable GPS periodically to conserve battery at the cost of accuracy between readings, or continuously in real-time.
noteThe Notecard will not turn on the GPS module until it has made a successful cellular connection upon startup to obtain the current time. Once the Notecard has the time, GPS is available for use, regardless of the state of a cellular connection.
There are also other functions on the Notecard that require the time to be set.
Sampling GPS Readings With Periodic Mode
If you prefer to enable GPS readings on an interval, use
periodic mode. In this mode, the Notecard enables GPS at a frequency you
define using either a set number of seconds or using a voltage-variable value.
In both cases, regardless of the periodic value, the GPS module
will only turn on to update the location if the Notecard has moved since the
last time GPS was enabled. The seconds value sets the minimum interval at
which the Notecard will enable its GPS.
Sampling at Predefined Intervals
To activate the GPS module on the Notecard every 600 seconds (at most, and only
if motion is detected), set mode to periodic and use the seconds argument
in a card.location.mode request:
This will return an object confirming that the Notecard is in periodic mode and that GPS should be enabled no more frequently than once every 600 seconds:
{
"mode": "periodic",
"seconds": 600
}Once enabled, use the card.location request to monitor connection status
and location.
While waiting for the Notecard to obtain a GPS fix, expect to see intermediate
status messages in response to card.location requests.
// When the module is still inactive
{
"status": "GPS inactive {gps-inactive}",
"mode": "periodic"
}
// When the module has started
{
"status": "GPS started {gps-active} {gps-active}",
"mode": "periodic"
}
// When the module is active, but searching for GPS
{
"status": "GPS search (19 sec, 41dB SNR, 5 sats) {gps-active}
{gps-signal} {gps-sats}",
"mode": "periodic"
}You may see several variations of the second message before the module obtains
a fix. Once obtained, future card.location requests include the current
Notecard latitude (lat) and longitude (lon) values, as well as the Unix
epoch time that location was captured.
{
"status": "GPS updated (58 sec, 41dB SNR, 9 sats) {gps-active}
{gps-signal} {gps-sats} {gps}",
"mode": "periodic",
"lat": 42.577600,
"lon": -70.871340,
"time": 1598554399
}To preserve battery, when the Notecard is in periodic mode, GPS is only enabled
if the built-in accelerometer detects movement since the last GPS enable. If
the Notecard has not moved, a card.location request will indicate that GPS is
inactive and provide the last location reading.
{
"status": "GPS inactive {gps-inactive} {gps}",
"mode": "periodic",
"lat": 42.5776,
"lon": -70.87134,
"time": 1598557149
}Tracking GPS Location Readings
When operating in periodic mode, use the
card.location.track request to configure the Notecard to store
GPS readings in a Notefile. Note that the behavior in this section only
applies to the capture of location events. The rules for how and when those
events sync are the same as general sync settings defined with hub.set.
This will return an object confirming that tracking mode has started and
the minimum duration in seconds between Notes being placed in a Notefile. The
seconds value is the value set in a request to card.location.mode.
{
"seconds": 10,
"start": true
}By default, tracking notes are placed into a Notefile named _track.qo. To
define your own Notefile, use the file argument.
noteTracking data is available to view in Notehub, once synced, and includes a number of helpful fields that can be Routed to your cloud applications.
{
"bearing": 194.8890307950282,
"distance": 5.591816976119877,
"seconds": 36,
"hdop": 1,
"temperature": 49.625,
"time": 1598560691,
"usb": true,
"velocity": 0.014337992246461224,
"voltage": 4.727260437757979
}By default, tracking data will only be captured if the Notecard detects motion.
To add periodic tracking Notes when there is no movement, use the heartbeat
argument. You can also use the optional hours argument to capture heartbeat
tracking notes at a rate that differs from the rate when there is motion.
If you wish to initiate a sync to Notehub each time a tracking Note is
added to the Notecard, set the sync field to true (As of Notecard
firmware v1.5.5):
To turn tracking mode off, set the stop argument to true.
Always-on GPS With Continuous Mode
To set your Notecard to GPS Continuous mode, use the card.location.mode
request:
Which will return an object confirming that the Notecard is in continuous mode:
{"mode": "continuous"}Once enabled, use the card.location request to monitor connection status
and location:
While waiting for the Notecard to obtain a GPS fix, expect to see intermediate
status messages in response to card.location requests. Note: the Notecard
will not turn on the GPS module until it has made a successful cellular
connection upon startup to obtain the current time. Once the Notecard has
the time, GPS is available for use, regardless of the state of a cellular
connection.
// When the module is still inactive
{
"status": "GPS inactive {gps-inactive}",
"mode": "continuous"
}
// When the module is active, but searching for GPS
{
"status": "GPS search (19 sec, 41dB SNR, 5 sats) {gps-active}
{gps-signal} {gps-sats}",
"mode": "continuous"
}You may see several variations of the status message before the module obtains
a fix. Once obtained, future card.location requests include the current
Notecard latitude (lat) and longitude (lon) values, as well as the Unix
epoch time that location was captured.
{
"status": "GPS updated (58 sec, 41dB SNR, 9 sats) {gps-active}
{gps-signal} {gps-sats} {gps}",
"mode": "continuous",
"lat": 42.577600,
"lon": -70.871340,
"time": 1598554399
}Continuous Cellular & Continuous GPS
The Notecard does not support running both a continuous
cellular connection ({"req":"hub.set", "mode":"continuous"}) and continuous
GPS. If you attempt to set both cellular and GPS to continuous mode, the
Notecard will return an error. This applies both to card.location.mode
when the cellular connection is continuous, as well as hub.set if GPS has
been set in continuous mode.
{"err": "cannot simultaneously use continuous card.location.mode and hub.set modes"}If concurrent use of cellular and GPS is required in your solution, we recommend usage of an external GPS module.
Determining the Current GPS Mode
At any point, the GPS mode of the Notecard can be obtained by calling the
card.location.mode command with no arguments.
This will return the current GPS mode alongside additional meta data if geofencing and/or voltage-variable periods are enabled.
{ "mode": "continuous", "max": 100, "lat": 42.5776, "lon": -70.87134, "minutes": 2, "threshold": 4 }
Geofencing With the Notecard
The Notecard can be configured to trigger an immediate sync to Notehub when the
device moves beyond a geofence you
define. Use the lat and lon arguments
to set the center, and the max argument to specify the
number of meters from the center to set the geofence. You can also optionally
pass the minutes argument to specify a number of minutes the Notecard must
be outside of the geofence before its location is tracked.
The default value for minutes is 5.
This will return an object confirming that the geofence is enabled using the parameters provided.
{
"max": 100,
"mode": "periodic",
"lat": 42.5776,
"lon": -70.87134,
"minutes": 2
}Disabling GPS
When you no longer need to capture GPS data from the Notecard, turn it off with
a card.location.mode request and mode field set to off.
Which will return an object confirming that GPS is off:
{"mode": "off"}Even after GPS has been disabled, the Notecard keeps the last location obtained,
which can be retrieved at any time with a card.location request.
{
"status": "GPS is off {gps-inactive} {gps}",
"mode": "off",
"lat": 42.5776,
"lon": -70.87134,
"time": 1598555070
}If you wish to delete the last known location stored in the Notecard, use the
delete argument in a card.location.mode request.
Subsequent requests to card.location no longer provide location data, until
GPS is re-enabled and a new reading is captured.
{
"status": "GPS is off {gps-inactive} {gps}",
"mode": "off"
}