Gary Servin / ros_lib_melodic

ROS Serial library for Mbed platforms for ROS Melodic Morenia. Check http://wiki.ros.org/rosserial_mbed/ for more information.

Dependencies:   BufferedSerial

Dependents:   rosserial_mbed_hello_world_publisher_melodic Motortest Nucleo_vr_servo_project NucleoFM ... more

ROSSerial_mbed for Melodic Distribution

The Robot Operating System (ROS) is a flexible framework for writing robot software. It is a collection of tools, libraries, and conventions that aim to simplify the task of creating complex and robust robot behavior across a wide variety of robotic platforms.

The rosserial_mbed package allows to write ROS nodes on any mbed enabled devices and have them connected to a running ROS system on your computer using the serial port.

Hello World (example publisher)

Import programrosserial_mbed_hello_world_publisher_melodic

rosserial_mbed Hello World example for Melodic Morenia distribution

Last commit 08 Nov 2019 by Gary Servin

Running the Code

Now, launch the roscore in a new terminal window:

Quote:

$ roscore

Next, run the rosserial client application that forwards your MBED messages to the rest of ROS. Make sure to use the correct serial port:

Quote:

$ rosrun rosserial_python serial_node.py /dev/ttyACM0

Finally, watch the greetings come in from your MBED by launching a new terminal window and entering :

Quote:

$ rostopic echo chatter

See Also

More examples

Blink

/*
 * rosserial Subscriber Example
 * Blinks an LED on callback
 */
#include "mbed.h"
#include <ros.h>
#include <std_msgs/Empty.h>

ros::NodeHandle nh;
DigitalOut myled(LED1);

void messageCb(const std_msgs::Empty& toggle_msg){
    myled = !myled;   // blink the led
}

ros::Subscriber<std_msgs::Empty> sub("toggle_led", &messageCb);

int main() {
    nh.initNode();
    nh.subscribe(sub);

    while (1) {
        nh.spinOnce();
        wait_ms(1);
    }
}

Push

/*
 * Button Example for Rosserial
 */

#include "mbed.h"
#include <ros.h>
#include <std_msgs/Bool.h>

PinName button = p20;

ros::NodeHandle nh;

std_msgs::Bool pushed_msg;
ros::Publisher pub_button("pushed", &pushed_msg);

DigitalIn button_pin(button);
DigitalOut led_pin(LED1);

bool last_reading;
long last_debounce_time=0;
long debounce_delay=50;
bool published = true;

Timer t;
int main() {
    t.start();
    nh.initNode();
    nh.advertise(pub_button);

    //Enable the pullup resistor on the button
    button_pin.mode(PullUp);

    //The button is a normally button
    last_reading = ! button_pin;

    while (1) {
        bool reading = ! button_pin;

        if (last_reading!= reading) {
            last_debounce_time = t.read_ms();
            published = false;
        }

        //if the button value has not changed for the debounce delay, we know its stable
        if ( !published && (t.read_ms() - last_debounce_time)  > debounce_delay) {
            led_pin = reading;
            pushed_msg.data = reading;
            pub_button.publish(&pushed_msg);
            published = true;
        }

        last_reading = reading;

        nh.spinOnce();
    }
}

Diff: ros/msg.h

Revision:
0:04ac6be8229a
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ros/msg.h	Fri Nov 08 14:38:09 2019 -0300
@@ -0,0 +1,148 @@
+/*
+ * Software License Agreement (BSD License)
+ *
+ * Copyright (c) 2011, Willow Garage, Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *  * Neither the name of Willow Garage, Inc. nor the names of its
+ *    contributors may be used to endorse or promote prducts derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _ROS_MSG_H_
+#define _ROS_MSG_H_
+
+#include <stdint.h>
+#include <stddef.h>
+
+namespace ros
+{
+
+/* Base Message Type */
+class Msg
+{
+public:
+  virtual int serialize(unsigned char *outbuffer) const = 0;
+  virtual int deserialize(unsigned char *data) = 0;
+  virtual const char * getType() = 0;
+  virtual const char * getMD5() = 0;
+
+  /**
+   * @brief This tricky function handles promoting a 32bit float to a 64bit
+   *        double, so that AVR can publish messages containing float64
+   *        fields, despite AVV having no native support for double.
+   *
+   * @param[out] outbuffer pointer for buffer to serialize to.
+   * @param[in] f value to serialize.
+   *
+   * @return number of bytes to advance the buffer pointer.
+   *
+   */
+  static int serializeAvrFloat64(unsigned char* outbuffer, const float f)
+  {
+    const int32_t* val = (int32_t*) &f;
+    int32_t exp = ((*val >> 23) & 255);
+    if (exp != 0)
+    {
+      exp += 1023 - 127;
+    }
+
+    int32_t sig = *val;
+    *(outbuffer++) = 0;
+    *(outbuffer++) = 0;
+    *(outbuffer++) = 0;
+    *(outbuffer++) = (sig << 5) & 0xff;
+    *(outbuffer++) = (sig >> 3) & 0xff;
+    *(outbuffer++) = (sig >> 11) & 0xff;
+    *(outbuffer++) = ((exp << 4) & 0xF0) | ((sig >> 19) & 0x0F);
+    *(outbuffer++) = (exp >> 4) & 0x7F;
+
+    // Mark negative bit as necessary.
+    if (f < 0)
+    {
+      *(outbuffer - 1) |= 0x80;
+    }
+
+    return 8;
+  }
+
+  /**
+   * @brief This tricky function handles demoting a 64bit double to a
+   *        32bit float, so that AVR can understand messages containing
+   *        float64 fields, despite AVR having no native support for double.
+   *
+   * @param[in] inbuffer pointer for buffer to deserialize from.
+   * @param[out] f pointer to place the deserialized value in.
+   *
+   * @return number of bytes to advance the buffer pointer.
+   */
+  static int deserializeAvrFloat64(const unsigned char* inbuffer, float* f)
+  {
+    uint32_t* val = (uint32_t*)f;
+    inbuffer += 3;
+
+    // Copy truncated mantissa.
+    *val = ((uint32_t)(*(inbuffer++)) >> 5 & 0x07);
+    *val |= ((uint32_t)(*(inbuffer++)) & 0xff) << 3;
+    *val |= ((uint32_t)(*(inbuffer++)) & 0xff) << 11;
+    *val |= ((uint32_t)(*inbuffer) & 0x0f) << 19;
+
+    // Copy truncated exponent.
+    uint32_t exp = ((uint32_t)(*(inbuffer++)) & 0xf0) >> 4;
+    exp |= ((uint32_t)(*inbuffer) & 0x7f) << 4;
+    if (exp != 0)
+    {
+      *val |= ((exp) - 1023 + 127) << 23;
+    }
+
+    // Copy negative sign.
+    *val |= ((uint32_t)(*(inbuffer++)) & 0x80) << 24;
+
+    return 8;
+  }
+
+  // Copy data from variable into a byte array
+  template<typename A, typename V>
+  static void varToArr(A arr, const V var)
+  {
+    for (size_t i = 0; i < sizeof(V); i++)
+      arr[i] = (var >> (8 * i));
+  }
+
+  // Copy data from a byte array into variable
+  template<typename V, typename A>
+  static void arrToVar(V& var, const A arr)
+  {
+    var = 0;
+    for (size_t i = 0; i < sizeof(V); i++)
+      var |= (arr[i] << (8 * i));
+  }
+
+};
+
+}  // namespace ros
+
+#endif