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Merged
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Oct 18, 2025
Merged

Add UInt8MultiArray primitive type #89

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0a5e83c
Add UInt8MultiArray primitive type for custom binary protocols
zouri Oct 18, 2025
de01b27
update README.md
zouri Oct 18, 2025
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2 changes: 1 addition & 1 deletion README.md
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Expand Up @@ -267,7 +267,7 @@ bridge:

As seen in the [Quick Start](#quick-start), the *mqtt_client* can not only exchange arbitrary ROS messages with other *mqtt_clients*, but it can also exchange primitive message data with other non-*mqtt_client* MQTT clients. This allows ROS-based devices to exchange primitive messages with devices not based on ROS. The `primitive` parameter can be set for both ROS-to-MQTT (`bridge/ros2mqtt`) and for MQTT-to-ROS (`bridge/mqtt2ros`) transmissions.

If a ROS-to-MQTT transmission is configured as `primitive` and the ROS message type is one of the supported primitive ROS message types, the raw data is published as a string. The supported primitive ROS message types are [`std_msgs/String`](http://docs.ros.org/en/api/std_msgs/html/msg/String.html), [`std_msgs/Bool`](http://docs.ros.org/en/api/std_msgs/html/msg/Bool.html), [`std_msgs/Char`](http://docs.ros.org/en/api/std_msgs/html/msg/Char.html), [`std_msgs/UInt8`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt8.html), [`std_msgs/UInt16`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt16.html), [`std_msgs/UInt32`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt32.html), [`std_msgs/UInt64`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt64.html), [`std_msgs/Int8`](http://docs.ros.org/en/api/std_msgs/html/msg/Int8.html), [`std_msgs/Int16`](http://docs.ros.org/en/api/std_msgs/html/msg/Int16.html), [`std_msgs/Int32`](http://docs.ros.org/en/api/std_msgs/html/msg/Int32.html), [`std_msgs/Int64`](http://docs.ros.org/en/api/std_msgs/html/msg/Int64.html), [`std_msgs/Float32`](http://docs.ros.org/en/api/std_msgs/html/msg/Float32.html), [`std_msgs/Float64`](http://docs.ros.org/en/api/std_msgs/html/msg/Float64.html).
If a ROS-to-MQTT transmission is configured as `primitive` and the ROS message type is one of the supported primitive ROS message types, the raw data is published as a string. The supported primitive ROS message types are [`std_msgs/String`](http://docs.ros.org/en/api/std_msgs/html/msg/String.html), [`std_msgs/Bool`](http://docs.ros.org/en/api/std_msgs/html/msg/Bool.html), [`std_msgs/Char`](http://docs.ros.org/en/api/std_msgs/html/msg/Char.html), [`std_msgs/UInt8`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt8.html), [`std_msgs/UInt16`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt16.html), [`std_msgs/UInt32`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt32.html), [`std_msgs/UInt64`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt64.html), [`std_msgs/Int8`](http://docs.ros.org/en/api/std_msgs/html/msg/Int8.html), [`std_msgs/Int16`](http://docs.ros.org/en/api/std_msgs/html/msg/Int16.html), [`std_msgs/Int32`](http://docs.ros.org/en/api/std_msgs/html/msg/Int32.html), [`std_msgs/Int64`](http://docs.ros.org/en/api/std_msgs/html/msg/Int64.html), [`std_msgs/Float32`](http://docs.ros.org/en/api/std_msgs/html/msg/Float32.html), [`std_msgs/Float64`](http://docs.ros.org/en/api/std_msgs/html/msg/Float64.html), [`std_msgs/UInt8MultiArray`](http://docs.ros.org/en/api/std_msgs/html/msg/UInt8MultiArray.html).

If an MQTT-to-ROS transmission is configured as `primitive`, the MQTT message is interpreted and published as a primitive data type, if possible. The message is probed in the following order: `bool` ([`std_msgs/Bool`](http://docs.ros.org/en/api/std_msgs/html/msg/Bool.html)), `int` ([`std_msgs/Int32`](http://docs.ros.org/en/api/std_msgs/html/msg/Int32.html)), `float` ([`std_msgs/Float32`](http://docs.ros.org/en/api/std_msgs/html/msg/Float32.html)), `string` ([`std_msgs/String`](http://docs.ros.org/en/api/std_msgs/html/msg/String.html)).

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11 changes: 11 additions & 0 deletions mqtt_client/src/MqttClient.cpp
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Expand Up @@ -48,6 +48,7 @@ SOFTWARE.
#include <std_msgs/msg/u_int32.hpp>
#include <std_msgs/msg/u_int64.hpp>
#include <std_msgs/msg/u_int8.hpp>
#include <std_msgs/msg/u_int8_multi_array.hpp>

#include <rclcpp_components/register_node_macro.hpp>
RCLCPP_COMPONENTS_REGISTER_NODE(mqtt_client::MqttClient)
Expand Down Expand Up @@ -164,6 +165,12 @@ bool fixedMqtt2PrimitiveRos(mqtt::const_message_ptr mqtt_msg,
std_msgs::msg::Float64 msg;
msg.data = mqtt2float<double>(mqtt_msg);

serializeRosMessage(msg, serialized_msg);
} else if (msg_type == "std_msgs/msg/UInt8MultiArray") {
std_msgs::msg::UInt8MultiArray msg;
const std::string& str_msg = mqtt_msg->to_string();
msg.data = std::vector<uint8_t>(str_msg.begin(), str_msg.end());

serializeRosMessage(msg, serialized_msg);
} else {
throw std::domain_error("Unhandled message type (" + msg_type + ")");
Expand Down Expand Up @@ -251,6 +258,10 @@ bool primitiveRosMessageToString(
std_msgs::msg::Float64 msg;
deserializeRosMessage(*serialized_msg, msg);
primitive = std::to_string(msg.data);
} else if (msg_type == "std_msgs/msg/UInt8MultiArray") {
std_msgs::msg::UInt8MultiArray msg;
deserializeRosMessage(*serialized_msg, msg);
primitive = std::string(msg.data.begin(), msg.data.end());
} else {
found_primitive = false;
}
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