WEBVTT

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In the previous laboratory lesson, we saw how to use our ros2 topic to turn on or off a lead that is

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embedded on the Arduino board.

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And we also enable the communication between Ros two and Arduino using the serial port.

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In this lesson, we are going to develop a simple Arduino script that instead sends messages over the

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serial port.

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In the next lesson, we will develop our Ros two node in both Cplusplus and Python that reads these

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comments that are received from the serial port by the Arduino and republish them on a Ros two topic.

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And this way we will have enabled also the reverse communication that is the communication between Arduino

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and Ros two.

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And so basically Arduino will be able to publish messages within our Ros two topic.

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Let's start by opening the Arduino ID, and here let's create a new sketch.

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So a new script.

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So let's close the old one.

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And here in the setup function, which is called only once when the Arduino boots up.

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Let's initialize the communication with the serial port as we did in the previous lesson by using the

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function, begin from the serial library and let's begin this communication by using about rate of 115

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200.

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And also in this case, let's use a timeout.

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So let's set a timeout.

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Of one.

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In the loop function instead, which is the one that is executed repeatedly in each cycle of the microcontroller.

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We want to send a new message.

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So a new integer variable called X.

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So let's create this X variable as a global variable and let's initialize this 1 to 0.

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And so we want to publish this variable.

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So the this integer value in this serial port.

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To do so.

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In Arduino, we can use serial print line.

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So the print line function and let's publish the X variable.

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And then at the end of each loop, let's also increase this variable.

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So let's increment its value.

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Then in order to avoid executing this loop function too fast, let's also insert a small delay of 0.1.

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With this, we have completed our very simple script for Arduino that publish a message.

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So a counter on the serial port.

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At this point, we can save this script.

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So let's save it.

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And again, let's save it within our workspace and within the Arduino boot firmware and within the firmware

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sub folder.

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And let's call this one simple serial transmitter.

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And so let's save this script.

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Let's conclude this lesson by compiling this file in order to see that actually there are no errors.

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And so let's upload it into our Arduino board.

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So let's connect the board to the PC using an USB cable.

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And let's go to the tools here.

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The port.

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Let's select the port of your PC to which the Arduino board is connected and then click on upload.

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So this will compile again and upload the code into the Arduino.