# Using the Slamtec RPLIDAR on a Raspberry Pi ## Overview ![](https://cdn-learn.adafruit.com/assets/assets/000/073/396/medium800/sensors_all-together.jpg?1553031066) LIDAR is all the range\*. It's one of the fundamental sensing technologies of autonomous vehicles. It gives a system the ability to see how far away things are 360 degrees around it. We used the Garmin LIDAR range finder in [another guide](https://learn.adafruit.com/garmin-lidar-lite-range-finder). It works by sending out a pulse of modulated laser light which bounces off whatever it's aimed at and is read by an optical receiver. The time that takes is a measure of distance to the surface it bounced off of. While being very cool and very effective technology, it just looks in one direction. You could mount it on a stepper motor and repeatedly rotate and take a reading. Or you could use a 360 degree LIDAR system like the RPLIDAR from Slamtec. * See what I did there? ## Parts ### Slamtec RPLIDAR A1 - 360 Laser Range Scanner [Slamtec RPLIDAR A1 - 360 Laser Range Scanner](https://www.adafruit.com/product/4010) Is your favorite robot currently in a mid-life crisis? Does it need a new purpose or perhaps, _direction? _ Well now you can find your way with the affordable and easy to use **Slamtec RPLIDAR A1** You may have heard of LIDARs when people talk about... In Stock [Buy Now](https://www.adafruit.com/product/4010) [Related Guides to the Product](https://learn.adafruit.com/products/4010/guides) ![Close shot of lamtec RPLIDAR A1 - 360 Laser Range Scanner](https://cdn-shop.adafruit.com/640x480/4010-07.jpg) ### Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM [Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM](https://www.adafruit.com/product/3775) The Raspberry Pi 3 Model B is the most popular Raspberry Pi computer made, and the Pi Foundation knows you can always make a good thing _better_! And what could make the Pi 3 better? How about a _faster_ processor, 5 GHz WiFi, and updated Ethernet chip with PoE capability?... In Stock [Buy Now](https://www.adafruit.com/product/3775) [Related Guides to the Product](https://learn.adafruit.com/products/3775/guides) ![Angled shot of Raspberry Pi 3 - Model B+](https://cdn-shop.adafruit.com/640x480/3775-11.jpg) ### Adafruit PiTFT - 320x240 2.8" TFT+Touchscreen for Raspberry Pi [Adafruit PiTFT - 320x240 2.8" TFT+Touchscreen for Raspberry Pi](https://www.adafruit.com/product/1601) Is this not the cutest little display for the Raspberry Pi? It features a 2.8" display with 320x240 16-bit color pixels and a resistive touch overlay. The plate uses the high speed SPI interface on the Pi and can use the mini display as a console, X window port, displaying images or video... Out of Stock [Buy Now](https://www.adafruit.com/product/1601) [Related Guides to the Product](https://learn.adafruit.com/products/1601/guides) ![320x240 2.8 inch TFT and Touchscreen installed on Raspberry Pi with desktop showing](https://cdn-shop.adafruit.com/640x480/1601-00.jpg) ### USB cable - USB A to Micro-B [USB cable - USB A to Micro-B](https://www.adafruit.com/product/592) This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller Approximately 3 feet / 1 meter long In Stock [Buy Now](https://www.adafruit.com/product/592) [Related Guides to the Product](https://learn.adafruit.com/products/592/guides) ![USB cable - USB A to Micro-B - 3 foot long](https://cdn-shop.adafruit.com/640x480/592-01.jpg) ### 5V 2.5A Switching Power Supply with 20AWG MicroUSB Cable [5V 2.5A Switching Power Supply with 20AWG MicroUSB Cable](https://www.adafruit.com/product/1995) Our all-in-one 5V 2.5 Amp + MicroUSB cable power adapter is the perfect choice for powering single-board computers like Raspberry Pi, BeagleBone, or anything else that's power-hungry! This adapter was specifically designed to provide 5.25V, not 5V, but we still call it a 5V USB... In Stock [Buy Now](https://www.adafruit.com/product/1995) [Related Guides to the Product](https://learn.adafruit.com/products/1995/guides) ![MicroUSB power supply with bundled cable and U.S. plugs.](https://cdn-shop.adafruit.com/640x480/1995-02.jpg) # Using the Slamtec RPLIDAR on a Raspberry Pi ## 360 Degree LIDAR Instead of taking a step-and-read approach, the RPLIDAR drives the rotating scanner with a DC motor, continuously taking readings and making note of the scanner's angle with each one. Because of this approach, a single revolution is not guaranteed to give a reading for each possible angle, but over several rotations a full scan can be assembled. The animation below shows a different mechanical approach (using a rotating mirror instead of a rotating sensor) and only covers 180 degrees, but the concept is identical. It shows the general theory of operation: readings taken at different angles, combined to provide a map of distances from the sensor. Using this data a system can get a sense of the space around it. ![](https://cdn-learn.adafruit.com/assets/assets/000/071/818/medium800thumb/sensors_LIDAR-scanned-SICK-LMS-animation.jpg?1550850834 In the public domain by Wikipedia user Mike1024) # Using the Slamtec RPLIDAR on a Raspberry Pi ## Using the Slamtec RPLIDAR ![](https://cdn-learn.adafruit.com/assets/assets/000/071/865/medium800/sensors_rplidar.jpg?1551028482) ### Slamtec RPLIDAR A1 - 360 Laser Range Scanner [Slamtec RPLIDAR A1 - 360 Laser Range Scanner](https://www.adafruit.com/product/4010) Is your favorite robot currently in a mid-life crisis? Does it need a new purpose or perhaps, _direction? _ Well now you can find your way with the affordable and easy to use **Slamtec RPLIDAR A1** You may have heard of LIDARs when people talk about... In Stock [Buy Now](https://www.adafruit.com/product/4010) [Related Guides to the Product](https://learn.adafruit.com/products/4010/guides) ![Close shot of lamtec RPLIDAR A1 - 360 Laser Range Scanner](https://cdn-shop.adafruit.com/640x480/4010-07.jpg) The device interfaces through a serial connection and comes with a USB to serial adaptor, not unlike an FTDI adapter **(but not the same pinout as one).** Warning: The bundled USB adapter is functionally similar to an FTDI adapter, but does not have the same connections. As mentioned, the RPLIDAR interfaces using serial. Rx and Tx for data, and a digital input to turn the motor on and off. You can use these directly, or with the included USB to serial adapter. Get started by installing the module on the Raspberry Pi using pip (or use `pip3` if available): `pip install adafruit-circuitpython-rplidar` For now this supports CPython (tested on the Raspberry Pi, other single board computers may be different).  # Using the Slamtec RPLIDAR on a Raspberry Pi ## CPython on Raspberry Pi ![](https://cdn-learn.adafruit.com/assets/assets/000/073/407/medium800/sensors_all-together.jpg?1553032559) The simplest way to use the RPLIDAR with a Raspberry Pi is to interface through the bundled USB adapter. Connect a USB cable on the Raspberry Pi and then plug the other end into the LIDAR USB adapter board. Ensure the adapter board is fitted correctly onto the sensor per the instructions in the manual. ## PyGame We'll be using the 2.8" PiTFT display. See [this guide](https://learn.adafruit.com/adafruit-pitft-28-inch-resistive-touchscreen-display-raspberry-pi) for instructions on installing and configuring the required support software. We'll also need pyGame to provide that data plotting capabilities. See the [pyGame site for installation instructions](https://www.pygame.org/wiki/GettingStarted). ## The Code To use the RPLIDAR, you need to start the motor spinning and tell it to start taking readings. It will then stream each reading it takes until you tell it to stop. Each reading includes the distance sensed, and the angle of the reading. To make things easier, the Skoltech library provides a convenient wrapper for this functionality, and that's what we'll use for this guide. This example will consume data from the RPLIDAR and display it on a 2.8" PiTFT display. We start by setting up a few things. ```auto import os from math import cos, sin, pi, floor import pygame from adafruit_rplidar import RPLidar # Set up pygame and the display os.putenv('SDL_FBDEV', '/dev/fb1') pygame.init() lcd = pygame.display.set_mode((320,240)) pygame.mouse.set_visible(False) lcd.fill((0,0,0)) pygame.display.update() # Setup the RPLidar PORT_NAME = '/dev/ttyUSB0' lidar = RPLidar(None, PORT_NAME) # used to scale data to fit on the screen max_distance = 0 ``` Next we create a buffer in which to keep distance data. Each item in the list stores the distance measured at each degree for a complete rotation. We use this to maintain the most recent set of measurements even though each scan will be incomplete. ```auto scan_data = [0]*360 ``` We use the `iter_scans` function of the RPLIDAR object. This starts the motor and the scanning for us so we can skip that in our code.  `iter_scans` accumulates measurements for a single rotation and returns a list of tuples, from which we are interested in the second and third items. These are the angle and the distance measured at that angle. Both are floating point values. Once we have a scan, we step through each data point. The floor of the angle is taken and used as the index at which to store the measurement value. Because it is possible that multiple consecutive measurements in a scan could be close to the same angle (and thus having the same floor value) there is a small chance that some measurements are lost. But there is no real disadvantage to this, so it can be disregarded. ```auto scan_data = [0]*360 try: print(lidar.info) for scan in lidar.iter_scans(): for (_, angle, distance) in scan: scan_data[min([359, floor(angle)])] = distance process_data(scan_data) except KeyboardInterrupt: print('Stoping.') lidar.stop() lidar.disconnect() ``` Once we have updated `scan_data`, it is passed to the `process_data` function. The `process_data` function can do anything from finding the closest object, to choosing the best direction to move in. The only requirement is that it be as fast as possible. If it takes too long to process a scan, data from the RPLIDAR will eventually be dropped. Since we're constantly reading fresh data, dropping an occasional scan shouldn't be an issue. In this example we display the distance data on a PiTFT. The first step of a pass is to clear the display. Then it looks at each angle: 0-359. If the distance recorded for that angle is zero, it's because a reading hasn't be acquired for that angle yet, and we can safely ignore it. If there is a distance recorded for the angle, `max_distance` is adjusted as necessary to keep the display scaled to fit on the screen. The angle is converted to radians (from degrees) and the vector for the reading is converted to a cartesian coordinate which is then used to plot the data point on the display. After all measurements have been plotted, the display is updated. ```auto def process_data(data): global max_distance lcd.fill((0,0,0)) for angle in range(360): distance = data[angle] if distance > 0: # ignore initially ungathered data points max_distance = max([min([5000, distance]), max_distance]) radians = angle * pi / 180.0 x = distance * cos(radians) y = distance * sin(radians) point = (160 + int(x / max_distance * 119), 120 + int(y / max_distance * 119)) lcd.set_at(point, pygame.Color(255, 255, 255)) pygame.display.update() ``` ![](https://cdn-learn.adafruit.com/assets/assets/000/073/399/medium800thumb/sensors_rplidar-sweep.jpg?1553031275) ## Full code https://github.com/adafruit/Adafruit_Learning_System_Guides/blob/main/pi_rplidar/display_lidar_pi.py # Using the Slamtec RPLIDAR on a Raspberry Pi ## The Road Ahead ![](https://cdn-learn.adafruit.com/assets/assets/000/071/825/medium800/sensors_tire-track.jpg?1550868114 CC BT-SA 4.0 by Wikipedia user HopsonRoad) We have a Raspberry Pi consuming data from the RPLIDAR and displaying it on a screen, using the Skoltech library. There are several possible ways forward. Continuing on the Pi, different applications can be explored using the LIDAR data. Robot navigation would be a fun one. In a different direction, the library can be ported to CircuitPython and run on SAMD boards. Look forward to seeing that added to this guide in the near future. ## Featured Products ### Slamtec RPLIDAR A1 - 360 Laser Range Scanner [Slamtec RPLIDAR A1 - 360 Laser Range Scanner](https://www.adafruit.com/product/4010) Is your favorite robot currently in a mid-life crisis? Does it need a new purpose or perhaps, _direction? _ Well now you can find your way with the affordable and easy to use **Slamtec RPLIDAR A1** You may have heard of LIDARs when people talk about... In Stock [Buy Now](https://www.adafruit.com/product/4010) [Related Guides to the Product](https://learn.adafruit.com/products/4010/guides) ### Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM [Raspberry Pi 3 - Model B+ - 1.4GHz Cortex-A53 with 1GB RAM](https://www.adafruit.com/product/3775) The Raspberry Pi 3 Model B is the most popular Raspberry Pi computer made, and the Pi Foundation knows you can always make a good thing _better_! And what could make the Pi 3 better? How about a _faster_ processor, 5 GHz WiFi, and updated Ethernet chip with PoE capability?... In Stock [Buy Now](https://www.adafruit.com/product/3775) [Related Guides to the Product](https://learn.adafruit.com/products/3775/guides) ### Adafruit PiTFT - 320x240 2.8" TFT+Touchscreen for Raspberry Pi [Adafruit PiTFT - 320x240 2.8" TFT+Touchscreen for Raspberry Pi](https://www.adafruit.com/product/1601) Is this not the cutest little display for the Raspberry Pi? It features a 2.8" display with 320x240 16-bit color pixels and a resistive touch overlay. The plate uses the high speed SPI interface on the Pi and can use the mini display as a console, X window port, displaying images or video... Out of Stock [Buy Now](https://www.adafruit.com/product/1601) [Related Guides to the Product](https://learn.adafruit.com/products/1601/guides) ### USB cable - USB A to Micro-B [USB cable - USB A to Micro-B](https://www.adafruit.com/product/592) This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller Approximately 3 feet / 1 meter long In Stock [Buy Now](https://www.adafruit.com/product/592) [Related Guides to the Product](https://learn.adafruit.com/products/592/guides) ### 5V 2.5A Switching Power Supply with 20AWG MicroUSB Cable [5V 2.5A Switching Power Supply with 20AWG MicroUSB Cable](https://www.adafruit.com/product/1995) Our all-in-one 5V 2.5 Amp + MicroUSB cable power adapter is the perfect choice for powering single-board computers like Raspberry Pi, BeagleBone, or anything else that's power-hungry! This adapter was specifically designed to provide 5.25V, not 5V, but we still call it a 5V USB... In Stock [Buy Now](https://www.adafruit.com/product/1995) [Related Guides to the Product](https://learn.adafruit.com/products/1995/guides) ## Related Guides - [PiGRRL - Raspberry Pi Gameboy](https://learn.adafruit.com/pigrrl-raspberry-pi-gameboy.md) - [Pi Hole Ad Detection Display with PiTFT](https://learn.adafruit.com/pi-hole-ad-pitft-tft-detection-display.md) - [RasPipe: A Raspberry Pi Pipeline Viewer, Part 1](https://learn.adafruit.com/raspipe-a-raspberry-pi-pipeline-viewer.md) - [Cupcade: the Raspberry Pi Micro Arcade Cabinet](https://learn.adafruit.com/cupcade-raspberry-pi-micro-mini-arcade-game-cabinet.md) - [SnapPiCam Raspberry Pi Camera](https://learn.adafruit.com/snappicam-raspberry-pi-camera.md) - [Raspberry Pi radio player with touchscreen](https://learn.adafruit.com/raspberry-pi-radio-player-with-touchscreen.md) - [Touchscreen Pi Timelapse Controller](https://learn.adafruit.com/touchscreen-pi-timelapse-controller.md) - [PiPhone - A Raspberry Pi based Cellphone](https://learn.adafruit.com/piphone-a-raspberry-pi-based-cellphone.md) - [RasPipe: A Raspberry Pi Pipeline Viewer, Part 2](https://learn.adafruit.com/raspipe-a-raspberry-pi-pipeline-viewer-part-2.md) - [Adafruit PiTFT - 2.8" Touchscreen Display for Raspberry Pi](https://learn.adafruit.com/adafruit-pitft-28-inch-resistive-touchscreen-display-raspberry-pi.md) - [Ultimate Youtube Live Camera](https://learn.adafruit.com/ultimate-youtube-live-camera.md) - [AstroPrint 3D Printing](https://learn.adafruit.com/astroprint-3d-printing.md) - [Processing on the Raspberry Pi & PiTFT](https://learn.adafruit.com/processing-on-the-raspberry-pi-and-pitft.md) - [Mini Mac Pi](https://learn.adafruit.com/mini-mac-pi.md) - [apt.adafruit.com](https://learn.adafruit.com/apt-adafruit-com.md)