Paparazzi UAS  v5.18.0_stable-1-g6993852-dirty
Paparazzi is a free software Unmanned Aircraft System.
 All Data Structures Namespaces Files Functions Variables Typedefs Enumerations Enumerator Macros Modules Pages
sonar_pwm module

Driver for a PWM based sonar range sensor

Reads sensor using PWM input and outputs sonar distance to object in [cm]

Why PWM over ADC: One only needs to connect GND, VCC and one more signal wire, same as ADC but not the disadvantages of ADC sensors noise

Sensor example: Maxbotix LV-EZ1

Example for airframe file

Add to your firmware section: This example contains all possible configuration options, not all of them are mandatory!

1 <module name="sonar_pwm">
2  <define name="USE_SONAR" value="TRUE" />
3  <define name="SONAR_OFFSET" value="0.1234" />
4  <define name="SONAR_SCALE" value="SONAR_PWM_PERIOD" />
5  <define name="SONAR_MIN_RANGE" unit="m" value="0.44" />
6  <define name="SONAR_MAX_RANGE" unit="m" value="3.0" />
7  <define name="SONAR_COMPENSATE_ROTATION" value="TRUE" />
8  <define name="SONAR_UPDATE_ON_AGL" value="TRUE" />
9  <define name="SONAR_PWM_PERIOD" value="4096" />
10  <define name="SONAR_PWM_OFFSET" value="20" />
11  <define name="SONAR_USE_PWM_FILTER" value="TRUE" />
12  <define name="SONAR_MEDIAN_SIZE" value="9" />
13  <define name="SENSOR_SYNC_SEND_SONAR" />
14  <configure name="SONAR_PWM_CHANNEL" value="PWM_INPUTx" />
15 </module>

Module configuration options

Configure Options

  • name: SONAR_PWM_CHANNEL value: PWM_INPUTx
    Description: Select PWM input channel for sensor to use e.g. PWM_INPUT1

Define Options

  • name: USE_SONAR value: TRUE
    Description: Activate use of sonar in INS extended filter (only rotorcraft) or not if one only wants to measure distance
  • name: SONAR_OFFSET value: 0.1234
    Description: Sensor offset in CM, as in where one onts zero to be, default is 0
  • name: SONAR_SCALE value: SONAR_PWM_PERIOD
    Description: Sensor scale
  • name: SONAR_MIN_RANGE value: 0.44
    Description: If defined, set limit to minimum value reported, default 0.15
  • name: SONAR_MAX_RANGE value: 3.0
    Description: If defined, set limit to maximum value reported, default 6.0
  • name: SONAR_COMPENSATE_ROTATION value: TRUE
    Description: Compensate AGL for body rotation, if not defined, defaults to FALSE
  • name: SONAR_UPDATE_ON_AGL value: TRUE
    Description: Updates the AGL value in state,if not defined, defaults to FALSE
  • name: SONAR_PWM_PERIOD value: 4096
    Description: period in microsec (e.g. 4096 for 12 bits sensor)
  • name: SONAR_PWM_OFFSET value: 20
    Description: initial offset on the raw pwm signal if needed (default: 820usec)
  • name: SONAR_USE_PWM_FILTER value: TRUE
    Description: Enable or disable a median filter on the sensor output values
  • name: SONAR_MEDIAN_SIZE value: 9
    Description: If median filter is enabled then set this option to filter the output more(or less), default is 7
  • name: SENSOR_SYNC_SEND_SONAR value: None
    Description: If defined, sends raw and scaled sonar values, useful for debugging sensor issues

Module functions

Init Functions

These initialization functions are called once on startup.

Periodic Functions

These functions are called periodically at the specified frequency from the module periodic loop.

  • sonar_pwm_read()
    • Frequency in Hz: 20
    • Autorun: LOCK
      Periodic function automatically starts after init and can't be stopped.

Files

Header Files

The following headers are automatically included in modules.h

Source Files

Raw sonar_pwm.xml file:

<!DOCTYPE module SYSTEM "module.dtd">
<module name="sonar_pwm" dir="sonar">
<doc>
<description>
Driver for a PWM based sonar range sensor
Reads sensor using PWM input and outputs sonar distance to object in [cm]
Why PWM over ADC:
One only needs to connect GND, VCC and one more signal wire, same as ADC but not the disadvantages of ADC sensors noise
Sensor example: Maxbotix LV-EZ1
</description>
<configure name="SONAR_PWM_CHANNEL" value="PWM_INPUTx" description="Select PWM input channel for sensor to use e.g. PWM_INPUT1"/>
<define name="USE_SONAR" value="TRUE" description="Activate use of sonar in INS extended filter (only rotorcraft) or not if one only wants to measure distance"/>
<define name="SONAR_OFFSET" value="0.1234" description="Sensor offset in CM, as in where one onts zero to be, default is 0"/>
<define name="SONAR_SCALE" value="SONAR_PWM_PERIOD" description="Sensor scale"/>
<define name="SONAR_MIN_RANGE" value="0.44" unit="m" description="If defined, set limit to minimum value reported, default 0.15"/>
<define name="SONAR_MAX_RANGE" value="3.0" unit="m" description="If defined, set limit to maximum value reported, default 6.0"/>
<define name="SONAR_COMPENSATE_ROTATION" value="TRUE" description="Compensate AGL for body rotation, if not defined, defaults to FALSE"/>
<define name="SONAR_UPDATE_ON_AGL" value="TRUE" description="Updates the AGL value in state,if not defined, defaults to FALSE"/>
<define name="SONAR_PWM_PERIOD" value="4096" description="period in microsec (e.g. 4096 for 12 bits sensor)"/>
<define name="SONAR_PWM_OFFSET" value="20" description="initial offset on the raw pwm signal if needed (default: 820usec)"/>
<define name="SONAR_USE_PWM_FILTER" value="TRUE" description="Enable or disable a median filter on the sensor output values"/>
<define name="SONAR_MEDIAN_SIZE" value="9" description="If median filter is enabled then set this option to filter the output more(or less), default is 7"/>
<define name="SENSOR_SYNC_SEND_SONAR" description="If defined, sends raw and scaled sonar values, useful for debugging sensor issues"/>
</doc>
<dep>
<depends>pwm_meas</depends>
</dep>
<header>
<file name="sonar_pwm.h" />
</header>
<init fun="sonar_pwm_init()" />
<periodic fun="sonar_pwm_read()" freq="20" />
<makefile target="ap">
<file name="sonar_pwm.c" />
<define name="SONAR_PWM_CHANNEL" value="$(SONAR_PWM_CHANNEL)" cond="ifdef SONAR_PWM_CHANNEL" />
<define name="$(SONAR_PWM_CHANNEL)_TICKS_PER_USEC" value="1" />
<define name="USE_$(SONAR_PWM_CHANNEL)" value="PWM_PULSE_TYPE_ACTIVE_LOW" />
</makefile>
</module>