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Version: 2.9.0

Create Luos services

As a developer, you will always develop your functionalities as services into packages and never into the main() program.


Make sure to read and understand the package section before reading this page.

How to create and initialize a service

To create a service, you have to call this function:

service_t* Luos_CreateService(void* callback, service_type_t type, char* default_alias, revision_t revision);

The returned service_t* is a service structure pointer that will be useful to make your service act in the network after this initialization.

callback is a pointer to a callback function called by Luos engine when a service receives messages from other services (see messages for more details). This function needs to have a specific format:

void Service_MsgHandler(service_t *service, msg_t *msg)
  • service is the service pointer of the service receiving the data (basically, it is your service).
  • msg is the message your service received.

type is the type of the new service represented by a number. Some basic types (e.g. DISTANCE_MOD, VOLTAGE_MOD, etc.) are already available in the service_type_t enum structure of Luos engine. You can also add your own.

default alias is the alias by default for your new service (e.g. Myservice02). This alias is the one your service will use if no other service have the same and if no other alias is set by the user. Aliases have a maximum size of 16 characters.

revision is the revision number of the service you are creating and which will be accessible via Pyluos.

Following the packages rules, here is a code example for a button service:

service_t* service_btn;

static void Button_MsgHandler(service_t *service, msg_t *msg)
// Manage received messages

void Button_Init(void)
revision_t ButtonRevision = {.major = 0, .minor = 0, .build = 7};

service_btn = Luos_CreateService(Button_MsgHandler, STATE_TYPE, "button", ButtonRevision);

void Button_Loop(void)

Services categories

To make your development as clean as possible, you have to understand into which category (Driver or App) each service of the project is located.

By following the categories guidelines, you will be able to make clean and reusable functionalities.

Drivers guidelines

A driver is a type of service that handles hardware. Motors, distance sensors, LEDs are all drivers.

By designing a driver, you have to keep the following rules in mind:

You can have multiple driver services on the same nodeHardware element (MCU) hosting and running Luos and hosting one or several services. managing different hardware functionalities of your board. It is up to you to sort them depending on your design.

Apps guidelines

An application or app is a type of service that only manages software items such as functions or algorithms. Apps use other services to make your device act, operate, and behave. Apps can be placed in any nodeHardware element (MCU) hosting and running Luos and hosting one or several services. on a Luos network without any hardware or code modifications. However, the choice of the hosting node can impact the global performance of the system.

By designing an app, you have to keep the following rules in mind:


If the data structures used are not standard, the gate services could be completely unable to manage them.

Apps are the embedded smartness of your device, and at least one of them should run a network detection in order to map every service in every node in your device and make it work properly. Go to the Routing table page for more information.

Services accessibility

You can define and manage the accessibility of services.

This accessibility allows you to specify the access the services can deal with. For example, a STATE_TYPE service (which can handle a basic True/False state) can be used either for a button (read-only) or a relay (write-only).

By default, when you create a new service, it will be on READ_WRITE_ACCESS, telling any other services that they can "send to" or "receive from" this new service. You can change this configuration if you want to.

Services can have the following accessibility:


For example, from the previous initialization example function of the button service, we should specify the accessibility of the service as READ_ONLY_ACCESS:

service_t* service_btn;

void Button_Init(void)
revision_t ButtonRevision = {.major = 0, .minor = 0, .build = 7};

service_btn = Luos_CreateService(Button_MsgHandler, STATE_TYPE, "button", ButtonRevision);

service_btn->access = READ_ONLY_ACCESS;

This doesn't change anything else on your service code as it allows external services to know the accessibility of your service.


Luos engine enables sending and receiving messages from services with a straightforward API.

Luos engine's APIs

Luos engine includes the following tools to integrate more capabilities and functionalities to manage your messages:

Send a Luos messageLuos_SendMsg(service_t *service, msg_t *msg);error_return_t
Send a timestamped Luos messageLuos_SendTimestampMsg(service_t *service, msg_t *msg, time_luos_t timestamp);error_return_t
Read a Luos messageLuos_ReadMsg(service_t *service, msg_t **returned_msg);error_return_t
Send the remaining data in case of long messagesLuos_SendData(service_t *service, msg_t *msg, void *bin_data, uint16_t size);void
Receive the remaining data in case of long messagesLuos_ReceiveData(service_t *service, msg_t *msg, void *bin_data);data size at the end of reception
Send data stored in a streaming channelLuos_SendStreaming(service_t *service, msg_t *msg, streaming_channel_t *stream);void
Receive data from a streaming channelLuos_ReceiveStreaming(service_t *service, msg_t *msg, streaming_channel_t *stream);error_return_t
Share network's baudrateLuos_SendBaudrate(service_t *service, uint32_t baudrate);void
Get the total ticks number since the initializationLuos_GetSystick(void);uint32_t
Subscribe to a new topic for pub/sub messagesLuos_TopicSubscribe(service_t *service, uint16_t topic);error_return_t
Unsubscribe from a topic for pub/sub messagesLuos_TopicUnsubscribe(service_t *service, uint16_t topic);error_return_t
Activate/Deactivate message filtering for global receptionLuos_SetFilterState(uint8_t state, service_t *service);void