ASR DBO433 Differential Barometer Altimeter OEM Module User Manual

: June 5, 2024
: ASR

Table of Contents

ASR DBO433 Differential Barometer Altimeter OEM Module
Features
Overview
Modes
Specifications
Pinout
Typical Characteristics
Commands
Output
SETUP
References
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ASR DBO433 Differential Barometer Altimeter OEM Module

Features

Integrated MCU
Corrected atmospheric pressure readings
Derived elevations with customizable datum
Temperature readings
Multi-node capable
Simple serial interface
Metric or Imperial output units

Application Examples

Indoor elevations
Building pressurization monitoring
Multi-node telemetry networks
Altitude reference for UAVs

Overview

The DBOxxx series differential barometer/altimeter (patent pending) OEM module provides atmospheric pressures and derived elevations at a rover using corrections transmitted from a stationary base. In traditional systems elevations are calculated based on pressure readings for a stand-alone unit and are subject to the errors inherent with environmental changes in pressure. This versatile engine offers three modes of operation detailed below.

Modes

Determining floating rover elevations based on corrections (black arrow) from a fixed base. In this application, the rover outputs a corrected elevation as it is raised or lowered relative to the ambient atmospheric pressure (blue arrows). When used inside an enclosed space such as a building both units must be located within. Multiple rovers can use the same base.
Determining a fixed rover pressure difference based on corrections (black arrow) from a fixed base. In this application, the rover outputs a corrected pressure (grey arrow) inside an enclosed space such as a building (grey rectangle) relative to the ambient atmospheric pressure (blue arrows). The base must be located outside the enclosed space. Multiple rovers can use the same base.
Multi-node telemetry. In this application, the rover receives remote uncorrected pressure and temperature from multiple bases. The pressure data is absolute and not differentially corrected.

Specifications

Differential Pressure Accuracy: +/- 0.028 mbar (+/- 25cm) RMS
Absolute Pressure Accuracy: +/- 2 mbar
Temperature Accuracy: +/- 1 C
Operating Temperature: -20C to 70C
Current: 20-120mA peak @ 5VDC (DBO433/DBO915), 20-130mA peak @ 5VDC (DBO868)
Dimensions: (L x W x H): 82mm x 32mm x 18mm
Range: 1Km (DBO433/DBO915), 5Km (DBO868)
Voltage: 3.8 – 15 VDC
Weight: 30g

Pinout

Serial communication parameters are 9600bps (N,8,1). The DTR/RTS signal pin is only required to update the firmware.

Typical Characteristics

Modules were stationary for testing at a set fixed datum elevation of 0m.

Commands

The general command syntax is a command,{x{,y}} followed by CR+LF.

Output

On initialization the unit will send the string ASR DBOxxx v y.y where:

xxx model number (433,868 or 915 MHz)
y.y firmware revision number

Base output format is as follows:
NetID,NodeID,B,Units,Local Pressure, Local Elevation, Local Temperature*Checksum

Rover output (absolute mode default) format is as follows:
NetID,NodeID,R,Units,Local Pressure, Local Elevation, Local Temperature*Checksum

Rover output (base telemetry ping response) format is as follows:
NetID,BaseNodeID,T,Units,Remote Pressure, Remote Elevation, Remote Temperature*Checksum

Rover output (differential mode) format is as follows, output will be ,A, (preset) until set:
NetID,NodeID,D,BaseNodeID,Units, Differential Pressure,Pressure Residual, Local Elevation Datum, Differential Elevation, Elevation Residual, Local Temperature,Remote TemperatureChecksum
Checksum is a hex value calculated by applying XOR on each character in the string up to but not including the asterisk (). Base NodeID must be an available node in the rover telemetry stream output for commands 4 and 5 to output differential results. Command 8,1 is used to inverse the differential elevations at the rover when the base is moving relative to a stationary rover in mode A. When enabled the BaseNodeID in the differential output will be preceded by a negative sign. Sending 8,0 will set the module back to noninversed output (default). This would be useful in an application such as an altitude reference for a UAV where the base is onboard and transmitting results to a stationary rover on the ground.

SETUP

The following is the initial setup procedure:

Select BASE jumper position on the base.
Send 1, NetID to base.
Send 2, NodeID to base.
Select ROVER jumper position on the rover.
Send 1, NetID to the rover.
Send 2, NodeID to the rover.
Send 3, Units to the rover.
Send 4, Elevation Datum, Base NodeID to the rover.
Send 5, to the rover (once datum residuals are acceptable in step 8).

NetID, NodeID, and Units settings are persistent and will be retained when power cycled. Only steps 8-9 above are required for a differential solution on subsequent power-ups. Do not move the modules during the calibration in step 8.

Demo Software
The Differential Barometer Demo software is available for download on our website at https://[www.asr-web.com/support](http://www.asr-web.com/support) and allows users to evaluate the capabilities of the system.
After installation edit the settings.txt file in the program installation directory to set the parameters.

Line 1: port number
When connected to the base, pressure and elevation graphs are absolute readings. Only the base temperature is displayed in this mode. The range corresponding to 0 on the graphs is shown in brackets in each title. The left buttons on the bottom left will be labeled NetID (x) where x is the current NetID and NodeID (y) where y is the current NodeID . To set a new NetID or NodeID enter it into the corresponding text box and click the button. The current Units can be changed on the bottom. In this mode the Datum button and NodeID combo box are disabled. The Reset button the right will clear the graphs.

When connected to the rover, pressure and elevation graphs are absolute readings until a datum is set. Only the rover temperature is displayed in this mode. The range corresponding to 0 on the graphs is shown in brackets in each title. The left buttons on the bottom left will be labeled NetID (x) where x is the current NetID and NodeID (y) where y is the current NodeID. To set a new NetID or NodeID enter it into the corresponding text box and click the button. The current Units can be changed on the bottom. In this mode the Datum button and NodeID combo box on the bottom right are disabled until base telemetry is received on the same NetID. The Reset button to the right will clear the graphs.

When base telemetry is available the Datum button and NodeID combo box on the bottom right will become enabled. Absolute readings for available base telemetry can be viewed by choosing the Base NodeID using the NodeID combo box. To set the Elevation Datum enter it into the text box and click the Datum button. After the Datum button is clicked it will change to Adjust (x) where x is the current Elevation Residual as an average deviation from the preset datum, do not move the units during the calibration. To set the Elevation Datum click the Adjust (x) button and the label will change to Datum (y) where y is the current Elevation Datum and differential data will be displayed. In this mode both base and rover temperatures are displayed. The Reset button to the right will clear the graphs and return to absolute mode. The Resume button will continue with the previously defined differential solution.

A log.txt file in the application directory stores the output with a date/time stamp.

Firmware Updates

Firmware updates are available for download on our website at https://www .asr-web.com/support.
The following is the firmware update procedure:

Connect the OEM module to a USB-serial converter, the DSR/DTR line must be used.
Connect USB-serial converter to a port on your local machine.
Unzip the package.
Launch a command window.
Change the directory to the location of the package.
Invoke update.bat with a single parameter that specifies the serial port number to use.