 Please ask about problems and questions regarding this tutorial on answers.ros.org. Don't forget to include in your question the link to this page, the versions of your OS & ROS, and also add appropriate tags. |
SRF08 Ultrasonic Ranger
Description: In this tutorial, we will use a Mbed and a SRF08 Ultrasonic Ranger as a Range Finder.The SRF08 communicates with the Mbed over SPI/I2C.Tutorial Level: BEGINNER
Next Tutorial: Buzzer Module
Show EOL distros:
Contents
rosserial allows you to easily integrate Mbed-based hardware with ROS. This tutorial will explain how to use a SRF08 Ultrasonic ranger with a Mbed.
You will need an Mbed, a SRF08 Ultrasonic Ranger, and a way to connect your Ranger to your Mbed such as a breadboard or protoboard.The SRF08 Mbed library can be downloaded from here
The Code
1 /*
2 * rosserial SRF08 Ultrasonic Ranger Example
3 *
4 * This tutorial demonstrates the usage of SRF08 ultrasonic module
5 *
6 * Source Code Based on:
7 * http://wiki.ros.org/rosserial_arduino/Tutorials/SRF08%20Ultrasonic%20Range%20Finder
8 */
9
10 #include "mbed.h"
11 #include "SRF08.h"
12
13 #include <ros.h>
14 #include <ros/time.h>
15 #include <sensor_msgs/Range.h>
16
17 ros::NodeHandle nh;
18
19 sensor_msgs::Range range_msg;
20 ros::Publisher pub_range("/ultrasound", &range_msg);
21
22 char frameid[] = "/ultrasound";
23
24 #ifdef TARGET_LPC1768
25 SRF08 srf08(p9, p10, 0xE0); // Define SDA, SCL pin and I2C address
26 #elif defined(TARGET_KL25Z) || defined(TARGET_NUCLEO_F401RE)
27 SRF08 srf08(I2C_SDA, I2C_SCL, 0xE0); // Define SDA, SCL pin and I2C address
28 #else
29 #error "You need to specify a pin for the sensor"
30 #endif
31
32 Timer t;
33 int main()
34 {
35 t.start();
36 nh.initNode();
37 nh.advertise(pub_range);
38
39 range_msg.radiation_type = sensor_msgs::Range::ULTRASOUND;
40 range_msg.header.frame_id = frameid;
41 range_msg.field_of_view = 0.1; // fake
42 range_msg.min_range = 0.0;
43 range_msg.max_range = 6.47;
44
45 long range_time = 0;
46
47 while (1)
48 {
49 //publish the adc value every 50 milliseconds
50 //since it takes that long for the sensor to stablize
51 if (t.read_ms() >= range_time)
52 {
53 range_msg.range = srf08.read() / 100.0;
54 range_msg.header.stamp = nh.now();
55 pub_range.publish(&range_msg);
56 range_time = t.read_ms() + 50;
57 }
58
59 nh.spinOnce();
60 }
61 }
Launching the App
$ roscore
Run the serial node with the right serial port corresponding to your MBED board
$ rosrun rosserial_python serial_node.py _port:=/dev/ttyUSB0
$ rosrun rosserial_python serial_node.py /dev/ttyUSB0
Now watch the sensor's value on the pushed topic
$ rostopic echo /ultrasound
