Examples of devices are e.g. Maxbotix MB1210 or MB1010 The sensor can be used as a control or measuring tool to detect the range (distance) to a surfaces, used for example in AGL hold, terrain following or landing assist.
To be able to use the Sonar connected to an ADC input, just add this module in your airframe and set needed parameters.
SONAR_ADC_SCALE for common sensors: Maxbotix XL-MaxSonar part MB1210 where sensor VCC is 5v: 0.001855 Maxbotix LV-MaxSonar part MB1010 where sensor VCC is 5v: 0.002315
Add to your firmware section: This example contains all possible configuration options, not all of them are mandatory!
These initialization functions are called once on startup.
These functions are called periodically at the specified frequency from the module periodic loop.
<!DOCTYPE module SYSTEM "module.dtd">
<module name="sonar_adc" dir="sonar" task="sensors">
<doc>
<description>
A Sonar with an ADC output signal can be used as unidirectional rangefinder. Examples of devices are e.g. Maxbotix MB1210 or MB1010
The sensor can be used as a control or measuring tool to detect the range (distance) to a surfaces, used for example in AGL hold, terrain following or landing assist.
To be able to use the Sonar connected to an ADC input, just add this module in your airframe and set needed parameters.
Notes:
+ The maximum useful detection distance is 4m for common simple sonar based small sized sensors, even if datasheet e.g. states 7m.
For most ADC sonar rangefinder sensor devices, a sampling rate of at least 15Hz is supported. However, if measurements are taken at longer distances,
the time required for the ultrasonic pulse to return increases, which may limit the maximum achievable sampling rate.
It is recommended to adjust the SONAR_ADC_PERIODIC_FREQUENCY parameter according to the sensor's capabilities and the expected measurement range to ensure reliable readings.
+ If the distance is read but the scale is incorrect, adjust the SONAR_ADC_SCALE parameter to match the sensor's specifications.
The scale factor can also be determined experimentally by measuring a known distance and adjusting the scale until the output matches the expected value.
This Scale value adjustment can be performed real-time via the setting panel which make it a little more user friendly.
After the correct value is determined, save setting or manually add the value to the airframe file.
SONAR_ADC_SCALE for common sensors:
Maxbotix XL-MaxSonar part MB1210 where sensor VCC is 5v: 0.001855
Maxbotix LV-MaxSonar part MB1010 where sensor VCC is 5v: 0.002315
+ If the sensor is used in an airframe with landing gear, it is recommended to set the SONAR_ADC_OFFSET to the height of the landing gear, so that the AGL zero value is correct to the ground.
Keep in mind that most sonar sensors have a deadzone of 0.15m to 0.25m, so the AGL cannot be measured if landinggear shorter than the deadzone range.
+ There is an option to compensate the AGL value for body rotation, which is useful if e.g. a roll maneuver, the sensor is not pointing straight down it compensates the AGL value for the body rotation.
+ Also an option to filter the sensor output is available, which is useful if the sensor is noisy or has a lot of outliers, in case of a sonar, almost always the case.
+ Distance compensation for pressure and temperature are not implemented, keep in mind that sonar sensors are susceptible to temperature and pressure changes.
</description>
<configure name="SONAR_ADC_PORT" value="ADC_X" description="Set the ADC port the sonar sensor is connected to on your flightcontroller, defaults to ADC_3"/>
<configure name="USE_SONAR_ADC_AGL" value="TRUE|FALSE" description="Updates the AGL value in state,if not defined, defaults to FALSE"/>
<configure name="SONAR_ADC_COMPENSATE_ROTATION" value="TRUE|FALSE" description="Compensate AGL measurements for body rotation. Disabled by default"/>
<configure name="SONAR_ADC_USE_FILTER" value="TRUE|FALSE" description="Enable or disable a filter on the sonar output values, defaults to TRUE"/>
<configure name="SONAR_ADC_PERIODIC_FREQUENCY" value="30" description="Sensor readings in HZ"/>
<configure name="SONAR_ADC_LOWPASS_TAU" value="0.11" description="If filtering is enabled, then one optionally can set this value to filter the output more(or less). Defaults to 0.16"/>
<configure name="SONAR_ADC_SCALE" value="0.001789" description="Sensor scale factor [m/adc], defaults to 0.001855"/>
<define name="USE_SONAR" value="TRUE|FALSE" description="Activate use of sonar in INS extended filter (only rotorcraft), defaults to FALSE"/>
<define name="SONAR_ADC_OFFSET" value="0.56" description="Sensor offset in meters, as in where one wants zero to be, default is 0.0"/>
<define name="SONAR_ADC_MIN_RANGE" value="0.31" unit="m" description="If defined, set limit to minimum value the sensor can reliably measure, default 0.15m"/>
<define name="SONAR_ADC_MAX_RANGE" value="3.1" unit="m" description="If defined, set limit to maximum value the sensor can reliably measure, default 4.0m"/>
<define name="SONAR_ADC_SYNC_SEND" value="TRUE|FALSE" description="Send RAW and scaled message with each new measurement,useful for debugging sensor issues (default: FALSE)"/>
<define name="SONAR_ADC_RAW_OFFSET" value="0" description="sensor offset in [adc] units, defaults to 0"/>
</doc>
<settings>
<dl_settings NAME="Rangefinder">
<dl_settings NAME="Sonar ADC">
<dl_setting MAX="1" MIN="0" STEP="1" VAR="sonar_adc.update_agl" shortname="Update AGL"/>
<dl_setting MAX="0.006" MIN="0.001" STEP="0.00002" VAR="sonar_adc.scale" shortname="Scale"/>
</dl_settings>
</dl_settings>
</settings>
<dep>
<depends>adc</depends>
<provides>sonar</provides>
</dep>
<header>
<file name="sonar_adc.h"/>
</header>
<init fun="sonar_adc_init()"/>
<periodic fun="sonar_adc_periodic()" freq="SONAR_ADC_PERIODIC_FREQUENCY"/>
<periodic fun="sonar_adc_report()" freq="SONAR_ADC_PERIODIC_FREQUENCY" autorun="FALSE"/>
<makefile target="ap">
<configure name="SONAR_ADC_PORT" default="ADC_3" case="lower|upper"/>
<configure name="USE_SONAR_ADC_AGL" default="0"/>
<configure name="SONAR_ADC_COMPENSATE_ROTATION" default="0"/>
<configure name="SONAR_ADC_USE_FILTER" default="1"/>
<configure name="SONAR_ADC_PERIODIC_FREQUENCY" default="30"/>
<configure name="SONAR_ADC_LOWPASS_TAU" default="0.16"/>
<configure name="SONAR_ADC_SCALE" default="0.001855"/>
<define name="USE_$(SONAR_ADC_PORT_UPPER)"/>
<define name="SONAR_ADC_PORT" value="$(SONAR_ADC_PORT_UPPER)"/>
<define name="USE_SONAR_ADC_AGL" value="$(USE_SONAR_ADC_AGL)"/>
<define name="SONAR_ADC_PERIODIC_FREQUENCY" value="$(SONAR_ADC_PERIODIC_FREQUENCY)"/>
<define name="SONAR_ADC_USE_FILTER" value="$(SONAR_ADC_USE_FILTER)"/>
<file name="sonar_adc.c"/>
</makefile>
</module>
1.9.8