GP-BTDL Bluetooth SDI-12 Data Logger

Is over-the-air firmware updating supported on the GroPoint Bluetooth Datalogger?
GroPoint Bluetooth Dataloggers with firmware versions 3.3 and higher support FOTA updates. See the GP-BTDL manual for instructions.

Is the Bluetooth Datalogger compatible with non-GroPoint sensors?
Yes. The GroPoint Bluetooth datalogger can be used with other third party SDI-12 sensors as long as they conform to SDI-12 protocol, can run from a switched 9 V power supply, the sensor power draw does not exceed 50 mA continuous and 100 mA peak, and a 2 second power on delay is a sufficient warm up time. Sensors that require continuous power can be used if external power is supplied to the sensor.

Is the GP Reader app available on Apple devices?
At the moment, the Bluetooth SDI-12 Data Logger software GP Reader is only available for Android devices. Please let us know if you require iOS support so we can prioritize this work based on demand.

Which Android versions does the GP Reader app support?
Android 8 and higher.

What communication protocol and electrical interface does the GroPoint Bluetooth Datalogger support?
The GroPoint Bluetooth Datalogger only supports SDI-12 communication and electrical interface.

How do I connect my sensor that does not have a connector to the Bluetooth Datalogger?
To connect a sensor that does not have a connector, you will need to purchase an M12 5-pin code A male connector to attach to your sensor. The pin connections are:

Pin 1: Sensor power
Pin 2: None
Pin 3: None
Pin 4: SDI-12 I/O
Pin 5: GND

How many sensors can be connected to one Bluetooth Datalogger?
GroPoint Bluetooth Dataloggers follow the SDI-12 standard which supports up to 10 sensors on a single SDI-12 bus. GroPoint BTDL kits come with either a 4-port or 2-port expansion bar to connect multiple sensors to one BTDL.

How can I change my sensor address using the Bluetooth Datalogger?
Only one sensor can be attached when changing the sensor address. In the GP Reader app, press Change Address. The current sensor address is displayed and you can select a new one by dragging the blue dot around the wheel. Once an address is chosen, press Set Address.

Does the Bluetooth Datalogger need to be kept in a watertight enclosure?
The Bluetooth SDI-12 Datalogger enclosure is IP76 rated, which means it can withstand immersion in water up to one meter for 30 minutes under lab conditions. This is not considered an environmentally hardened enclosure. While you do not need an additional watertight enclosure, it is a good idea to keep the datalogger out of direct exposure to the elements. Covering it with a structure and raising it off the ground are both good ideas.

Is it possible to send custom SDI-12 commands to sensors using the Bluetooth Datalogger?
GP Reader has a transparent mode for sending SDI-12 commands to a connected sensor. Press and hold Measure to activate transparent command mode.

How can I change the logging interval on my Bluetooth Datalogger?
To change the logging interval, go to the configuration menu by pressing Config. Select the desired measurement interval from the drop down list then press Update. The BTDL cannot be logging while you change configuration settings so you must download any logged data, then stop and erase the logger.

How long does it take for the Bluetooth Datalogger to complete a measurement?
Total measurement time depends on the sensor or sensors being measured. There is always an initial 2 second power on delay, followed by the measurement sequence. Below is a breakdown of GPLP moisture and temperature measurement times:
2 segment: 1.4 s
3 segment: 1.6 s
4 segment: 2.0 s
5 segment: 2.1 s
6 segment: 2.6 s
8 segment: 3.6 s
If you have multiple sensors connected, the measurement times add together. For example, to measure three 8 segment GPLP sensors, total time is approximately 12.5 s.

What is the Local Log File feature and should I enable it?
The local log file feature logs all communication between the app and data logger. It is used for diagnostics if there is an issue with the BTDL. Enable this only for diagnostics because it slows down data download rates by roughly 15 percent.

What is the Daily Sampling feature?
Daily sampling conserves battery life by automatically adjusting the measurement interval based on temperature readings from a connected GroPoint GPLP Profile sensor. The logger checks temperature at a user defined time each day. If the temperature is below a user specified threshold, the logger switches to a daily sampling interval. If the temperature rises above the threshold, the logger returns to the regular measurement interval.

What format will data be downloaded in?
The default settings use .txt with a comma delimiter. This can be customized in the About menu of the GP Reader app. Supported file formats are .txt, .csv and .dat, with comma, semicolon or tab delimiters.

Each reading in the parsed data files includes date and time, followed by the sensor address, moisture measurements from each segment and then temperature measurements. For example, a 6 segment GPLP sensor line might look like:
2024-03-08 14:53,0,+30.9,+54.2,+51.3,+16.6,+27.5,+26.6,+23.1,+22.3,+21.8,+21.3,+21.5,+21.1,+21.0,+20.7,+20.6,+20.2,+20.5

How can I identify which data file belongs to a specific sensor?
Downloaded data files are named using the format {friendly name} (sensor serial number). For example, if the logger friendly name is MyLogger and the sensor serial is 600123, the file name is MyLogger (600123).txt.

Where can I find the downloaded data files from the GP Reader app on my Android device?
When you first connect GP Reader to a BTDL, you will be prompted to select a file location for the GPReader folder. Using the Documents folder is recommended for easy access. Files for the same logger and sensor append data automatically.

How do I export the data from my Android device to my PC so I can analyze it?
You can share files via email using the share button in GP Reader, located beside the About button. Alternatively, navigate to the GPReader folder and email selected files directly.

Will I lose my data if the batteries in my Bluetooth Datalogger run out?
Your data is stored safely in the logger even if the batteries die. During low battery states some data may become corrupted or missing, so replace batteries before downloading data. For AA configuration, we suggest using Energizer Lithium Ultimate and for C-cell we recommend SAFT LSH14 Li-SOCL-2.

How long will the batteries in my Bluetooth Datalogger last?
Battery life depends on measurement interval, number of measurements, number of sensors and operating temperature. For an estimate with GPLP sensors attached, see the Battery Capacity Calculator.

How can I tell if the batteries in my Bluetooth Datalogger are low?
GP Reader has a battery voltage indicator with colors:
Green: battery voltage is good
Yellow: change the batteries soon
Red: replace the batteries immediately

If your indicator is yellow, change batteries before logging. BTDLs can ship with 2 × AA batteries or a single C-cell. If you change the battery type, update the battery settings in your BTDL. Long press on the battery voltage indicator to select the correct type.

What are the battery requirements for the BTDL?
Max pulse current: at least 500 mA over 100 ms over the full temperature range.
Battery voltage: 3.6 V.
We recommend Energizer Lithium Ultimate for AA and SAFT LSH14 Li-SOCL-2 for C-cell.

What are the possible reasons my Bluetooth Datalogger will not start logging?
Several issues can prevent logging:

• GP Reader app or Bluetooth Datalogger firmware is out of date.
• Sensors are not connected or not responsive.
• Configured sensor addresses are incorrect or duplicated.
• Battery voltage is too low, check the voltage indicator in GP Reader.
• A faulty sensor may be affecting the SDI-12 bus; test each sensor individually.
• Protective plugs with internal connections attached to unused expansion bar ports may disrupt communication.
• Wiring between the sensor and datalogger does not match wiring diagrams.

What can cause my Bluetooth Datalogger to fail during data download or parsing and how can I resolve it?
Possible causes include:

• Outdated GP Reader app or BTDL firmware.
• Low battery power.
• Data corruption caused by low battery states.
• Missing data due to sensor connection issues or insufficient power.

If the issue persists, contact support@gropoint.com for help recovering data.

What should I do if an error occurs while downloading or parsing data?
If a download error occurs, the app prompts you to resume when you reconnect. Confirm sensors are still connected and that batteries are not low. If issues continue, enable Enable Local Log File in the About menu. This creates GPReaderLog.txt in the GPReader folder which you can send to support for diagnostics.
If parsing errors occur, send your raw data files to support@gropoint.com. Raw files use the logger friendly name and end in a three digit extension starting with .001.

What should I do if I am having trouble connecting via Bluetooth?
Some Android devices take longer to find the BTDL. Ensure the BTDL is powered, and give the device time to scan. If your device is not connecting reliably, toggle Bluetooth off and on to reset it. Location services must also be enabled in your device settings for GP Reader to connect to a BTDL.