PX4 · hamishwillee · Dec 17, 2024 · Nov 11, 2024 · Nov 13, 2024 · Nov 13, 2024
diff --git a/assets/hardware/sensors/lidar_lightware/sf45.png b/assets/hardware/sensors/lidar_lightware/sf45.png
diff --git a/assets/sf45/sf45_obstacle_map.png → ...ors/lidar_lightware/sf45_obstacle_map.png b/assets/sf45/sf45_obstacle_map.png → ...ors/lidar_lightware/sf45_obstacle_map.png
diff --git a/assets/hardware/sensors/lidar_lightware/sf45_plotjuggler.mp4 b/assets/hardware/sensors/lidar_lightware/sf45_plotjuggler.mp4
diff --git a/en/SUMMARY.md b/en/SUMMARY.md
@@ -242,6 +242,7 @@
     - [Barometers](sensor/barometer.md)
     - [Distance Sensors \(Rangefinders\)](sensor/rangefinders.md)
       - [Lightware Lidars (SF/LW)](sensor/sfxx_lidar.md)
+        - [Lightware SF45 Rotary Lidar](sensor/sf45_rotating_lidar.md)
       - [Ainstein US-D1 Standard Radar Altimeter](sensor/ulanding_radar.md)
       - [LeddarOne Lidar](sensor/leddar_one.md)
       - [Benewake TFmini Lidar](sensor/tfmini.md)

diff --git a/en/computer_vision/collision_prevention.md b/en/computer_vision/collision_prevention.md
diff --git a/en/sensor/rangefinders.md b/en/sensor/rangefinders.md
@@ -36,14 +36,14 @@ The rangefinders are enabled using the parameter [SENS_EN_MB12XX](../advanced_co
 
 ### Lightware LIDARs
 
-[Lightware SFxx Lidar](../sensor/sfxx_lidar.md) provide a broad range of lightweight "laser altimeters" that are suitable for many drone applications.
+[Lightware SFxx Lidar](../sensor/sfxx_lidar.md) provide a broad range of lightweight “laser altimeters” that are suitable for many drone applications.
 
 PX4 supports: SF11/c and SF/LW20.
 PX4 can also be used with the following discontinued models: SF02, SF10/a, SF10/b, SF10/c.
 
 Others may be supported via the [RaccoonLab Cyphal and DroneCAN Rangefinder Adapter](#raccoonlab-cyphal-and-dronecan-rangefinder-adapter) described below.
 
-PX4 also supports the [LightWare LiDAR SF45 Rotating Lidar](https://www.lightwarelidar.com/shop/sf45-b-50-m/) for [collision prevention](../computer_vision/collision_prevention.md#lightware-lidar-sf45-rotating-lidar) applications.
+PX4 also supports the [LightWare LiDAR SF45 Rotating Lidar](../sensor/sf45_rotating_lidar.md) for [collision prevention](../computer_vision/collision_prevention.md) applications.
 
 ### TeraRanger Rangefinders
 

diff --git a/en/sensor/sf45_rotating_lidar.md b/en/sensor/sf45_rotating_lidar.md
@@ -0,0 +1,125 @@
+# Lightware SF45/B Rotary Lidar
+
+LightWare [SF45/B](https://lightwarelidar.com/shop/sf45-b-50-m/) is an extremely small and light rotating Lidar with a range of 50m.
+It can be used to enable [Collision Prevention](../computer_vision/collision_prevention.md) without a companion computer.
+
+![LightWare SF45 rotating Lidar](../../assets/hardware/sensors/lidar_lightware/sf45.png)
+
+:::info
+The lidar driver is not included in the default build of PX4.
+You will need to [create and use a custom build](#add-the-driver-to-the-px4-build).
+:::
+
+## LightWare Studio Setup
+
+In the [LightWare Studio](https://www.lightwarelidar.com/resources-software) app set following values:
+
+| Parameter | Description |
+| --------- | ----------- |
+| Baud rate | 921600      |
+
+Make sure the scan angles are set so that nothing on the drone interferes with the measurements.
+The driver and [Collision Prevention](../computer_vision/collision_prevention.md) automatically handle angles different from the maximum angles.
+
+## Hardware Setup
+
+The rangefinder can be connected to any unused serial port, such as `TELEM2`.
+[Parameter Configuration](#parameter-configuration) explains how to configure the port to use and the other properties of the rangefinder.
+
+## PX4 Setup
+
+### Add the Driver to the PX4 Build
+
+The driver for this LiDar is not included in PX4 firmware by default.
+
+You will need to:
+
+1. Add the [lightware_sf45_serial](../modules/modules_driver_distance_sensor.md#lightware-sf45-serial) driver to firmware:
+   - Install and open [menuconfig](../hardware/porting_guide_config.md#px4-menuconfig-setup)
+   - In [menuconfig](../hardware/porting_guide_config.md#px4-menuconfig-setup), navigate to **Drivers > Distance sensors**
+   - Select/Enable `lightware_sf45_serial`
+2. [Build PX4](../dev_setup/building_px4.md) for your flight controller target and then upload the new firmware.
+
+### Parameter Configuration
+
+You will need to configure PX4 to indicate the serial port to which the sensor is connected (as per [Serial Port Configuration](../peripherals/serial_configuration.md)) and also the orientation and other properties of the sensor.
+
+The [parameters to change](../advanced_config/parameters.md) are listed in the table.
+
+| Parameter                                                                                                   | Description                                              |
+| ----------------------------------------------------------------------------------------------------------- | -------------------------------------------------------- |
+| <a id="SENS_EN_SF45_CFG"></a>[SENS_EN_SF45_CFG](../advanced_config/parameter_reference.md#SENS_EN_SF45_CFG) | Set to the serial port you have the sensor connected to. |
+| <a id="SF45_ORIENT_CFG"></a>[SF45_ORIENT_CFG](../advanced_config/parameter_reference.md#SF45_ORIENT_CFG)    | Set the orientation of the sensor (facing up or down)    |
+| <a id="SF45_UPDATE_CFG"></a>[SF45_UPDATE_CFG](../advanced_config/parameter_reference.md#SF45_UPDATE_CFG)    | Set the update rate                                      |
+| <a id="SF45_YAW_CFG"></a>[SF45_YAW_CFG](../advanced_config/parameter_reference.md#SF45_YAW_CFG)             | Set the yaw orientation                                  |
+
+## Testing
+
+You can confirm that the sensor is correctly configured by connecting QGroundControl, and observing that [OBSTACLE_DISTANCE](https://mavlink.io/en/messages/common.html#OBSTACLE_DISTANCE) is present in the [MAVLink Inspector](https://docs.qgroundcontrol.com/master/en/qgc-user-guide/analyze_view/mavlink_inspector.html).
+
+The obstacle overlay in QGC will look like this:
+
+![sf45 obstacle avoidance map shown in QGC](../../assets/hardware/sensors/lidar_lightware/sf45_obstacle_map.png)
+
+## Driver Implementation
+
+The [sensor driver](../modules/modules_driver_distance_sensor.md#lightware-sf45-serial) publishes the [ObstacleDistance](../msg_docs/ObstacleDistance.md) UORB Message that is used by PX4 [Collision Prevention](../computer_vision/collision_prevention.md).
+The measurements in each sector will correspond to the lowest measurement the sensor had in that corresponding sector.
+The data is then published to the [OBSTACLE_DISTANCE](https://mavlink.io/en/messages/common.html#OBSTACLE_DISTANCE) MAVLink message.
+
+## Troubleshooting
+
+### Common problems
+
+Start-up issues, jerky movements, or a lot of communication errors displayed with `lightware_sf45_serial status` could mean that the sensor is not getting enough power.
+
+According to its datasheet, the sensor needs 300 mA of current at 5V.
+The supplied cable is fairly long and when connected to the 5V supply, such as the flight controller `TELEM2` port, the voltage at the rangefinder may drop below the required level.
+One mitigation/alternative is to power the SF45 via a separate step-down converter from battery voltage, ensuring that there are 5V across the rangefinder itself.
+
+### Debugging with PlotJuggler
+
+Debugging problems with distance sensors is much easier if you can plot the [OBSTACLE_DISTANCE](https://mavlink.io/en/messages/common.html#OBSTACLE_DISTANCE) message in an x-y plot, because this lets you directly see the orientation of the measurement in respect of the drone.
+
+The video below shows how you can view such a plot in PlotJuggler.
+
+<video src="../../assets/hardware/sensors/lidar_lightware/sf45_plotjuggler.mp4" width="720" controls></video>
+
+In order to generate this kind of plot you will need to add the following Reactive Scripts to PlotJuggler.
+If you save these scripts and then add new data, you will see a new timeseries called `obstacle_distance_xy`, which is the same as is displayed in the video.
+
+**Global code, executed once:**
+
+```reactive
+obs_dist_xy = ScatterXY.new("obstacle_distance_xy")
+```
+
+**function(tracker_time)**
+
+```reactive
+obs_dist_xy:clear()
+
+i = 0
+angle_offset = TimeseriesView.find("obstacle_distance/angle_offset")
+increment = TimeseriesView.find("obstacle_distance/increment")
+
+while(true) do
+
+str = string.format("obstacle_distance/distances.%02d", i)
+distance = TimeseriesView.find( str )
+
+if distance == nil then break end
+angle = angle_offset:atTime(tracker_time) + i * increment:atTime(tracker_time)
+
+y = distance:atTime(tracker_time) * math.cos(math.rad(angle))
+x = distance:atTime(tracker_time) * math.sin(math.rad(angle))
+
+obs_dist_xy:push_back(x, y)
+
+i = i + 1
+end
+```
+
+::: tip
+To also see the fused `obstacle_distance`, you can just adapt the script to work on the `obstacle_distance_fused` message.
+:::
diff --git a/en/sensor/sfxx_lidar.md b/en/sensor/sfxx_lidar.md
@@ -1,18 +1,19 @@
-# LightWare SF1X/SF02/LW20 Lidar
+# LightWare Lidar (SF1X/SF02/LW20/SF45)
 
 LightWare develops a range of light-weight, general purpose, laser altimeters ("Lidar") suitable for mounting on UAVs.
 These are useful for applications including terrain following, precision hovering (e.g. for photography), warning of regulatory height limits, anti-collision sensing etc.
 
-![LightWare SF11/C Lidar](../../assets/hardware/sensors/lidar_lightware/sf11c_120_m.jpg)
+<img src="../../assets/hardware/sensors/lidar_lightware/sf11c_120_m.jpg" width="350px" alt="LightWare SF11/C Lidar"/>![LightWare SF45 rotating Lidar](../../assets/hardware/sensors/lidar_lightware/sf45.png)
 
 ## Supported Models
 
 The following models are supported by PX4, and can be connected to either the I2C or Serial bus (the tables below indicates what bus can be used for each model).
 
-| Model                                                      | Range (m) | Bus               | Description                                                     |
-| ---------------------------------------------------------- | --------- | ----------------- | --------------------------------------------------------------- |
-| [SF11/C](https://lightwarelidar.com/products/sf11-c-100-m) | 100       | Serial or I2C bus |                                                                 |
-| [LW20/C](https://lightware.co.za/products/lw20-c-100-m)    | 100       | I2C bus           | Waterproofed (IP67) with servo for sense-and-avoid applications |
+| Model                                                      | Range (m) | Bus               | Description                                                                                |
+| ---------------------------------------------------------- | --------- | ----------------- | ------------------------------------------------------------------------------------------ |
+| [SF11/C](https://lightwarelidar.com/products/sf11-c-100-m) | 100       | Serial or I2C bus |
+| [LW20/C](https://lightware.co.za/products/lw20-c-100-m)    | 100       | I2C bus           | Waterproofed (IP67) with servo for sense-and-avoid applications                            |
+| [SF45/B](../sensor/sf45_rotating_lidar.md)                 | 50        | Serial            | Rotary Lidar (Used for [Collision Prevention](../computer_vision/collision_prevention.md)) |
 
 ::: details Discontinued
 
@@ -62,15 +63,17 @@ VTOL vehicles may choose to also set [SF1XX_MODE](../advanced_config/parameter_r
 
 ## Serial Setup {#serial_hardware_setup}
 
+::: tip
+[SF45/B](../sensor/sf45_rotating_lidar.md) setup is covered in the linked document.
+:::
+
 ### Hardware
 
 The lidar can be connected to any unused _serial port_ (UART), e.g.: TELEM2, TELEM3, GPS2 etc.
 
 <!-- Would be good to show serial setup! -->
 
-<a id="serial_parameter_setup"></a>
-
-### Parameter Setup
+### Parameter Setup {#serial_parameter_setup}
 
 [Configure the serial port](../peripherals/serial_configuration.md) on which the lidar will run using [SENS_SF0X_CFG](../advanced_config/parameter_reference.md#SENS_SF0X_CFG).
 There is no need to set the baud rate for the port, as this is configured by the driver.