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Part 2: How to display the encoder output

1. Introduction

After we have created our Morse encoder application, we need to integrate a service that will exploit the output of the Morse encoder. As explained previously, each time that a letter is encoded, a Morse output is generated and the encoder application shares this output with the rest of the network. This output can be used by the display device of your preference (a speaker, a LED, etc.).

For this project, we have decided to use a Led driver service in order to display the Morse result on a simple LED light. Let’s see how it works.


To understand how to create a Luos driver service like the Led driver, make sure that you follow Your first service tutorial.

2. Led service example

In this tutorial, we have chosen to use a simple LED to demonstrate the output of the encoder algorithm. The LED will be able to blink each Morse character that was created by the encoder application. At this step, we have not yet created the input generator service, and for this reason, by default, the output of the application will be the word "S.O.S".

a. Integrate your Led driver to your project

The Led library creates a Luos service, that includes the driver for your board.


A service is a block of code which will provide a functionality. Services are able to communicate with any other service present in the Luos network. A service can be a driver for a hardware component that you want to use, or an application that defines only the software-oriented functionalities of your system.

b. Add Led_Init() and Led_Loop() functions into main.c

Now, we can go on with the integration of the Led service into our project’s main file.

In order to make the Led service work with your Morse encoder, we should call the function Led_Init() after the initialization of your encoder application and Luos, and then Led_Loop() after Luos_Loop() and Encoder_Loop(). Don’t forget to include your library’s header file led.h:

* @file main
* @brief main file of the project
* @author Yourself
* @version 0.0.0

#include "stm32f0xx_hal.h"
#include "luos.h"
#include "led.h"

* @brief main function
* @param None
* @return None
int main(void)

// Init
while (1)
// Loop

Because our Led service is a service of type STATE_TYPE, the encoder service will find it and use it as an output by default. It will work the same way for any other STATE_TYPE driver such as a speaker or a relay.

In our Led service, we can treat the messages of the command IOSTATE. This command shows that the message received contains 1 byte of data, with a value TRUE or FALSE (1 or 0), depending on the value we want to write to the LED pin.

The encoder is now able to light your LED!

3. Build and upload your project

You are now ready to build your project and upload it to your board. Finally you should see the message S.O.S encoded in Morse on your LED light. Let's go to the last part!