customize publish function in mqtt sample

[mschweig]

Hi, I  am currently testing the MQTT Communication with our IoT-Platform. 

I am successfully connected to the broker and I am able to receive messages from the subscribed topic. 

Now I want to publish my own messages and not just reply the received message from the subscribe function. 

Therefore I need to know how to edit the data_publish function and subsequently the MQTT_EVT_PUBLISH case in the mqtt_simple sample. 

Thanks in advance and best regards, 

Manuel

[mschweig]

For example I want to publish that string which can be used with our IoT-Platform: 

"200,myCustomTemperatureMeasurement,fahrenheit,75.2,F"

[Hakon]

Hey, can't you just call

data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE, "200,myCustomTemperatureMeasurement,fahrenheit,75.2,F", strlen("200,myCustomTemperatureMeasurement,fahrenheit,75.2,F"));

?

Just make sure you run it after subscribing.

[mschweig]

Hi, 

yes, ofc I can call this and it is being successfully published, but I would like to call it on a event, for example on button press. Or publish the current button state.

In would have used gpio_pin_read in while (1) and the use the data_publish function, but that does not work. 

while (1) {

                u32_t val = 0;
                gpio_pin_read(gpiob, PIN, &val);
                printk("Button: %d\n", val);

                char buffer[2];

                
                data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE,sprintf(buffer,"%u",val), 1);

Also tried it without conversion to string. 

Do you have a better solution how to solve that? 

Thanks!

[Linus]

Hi!

You are using sprintf() in the wrong way. It doesn't return a string, but the number of characters used in the result. Here's how you should use it:

sprintf(buffer, "%u", val);
data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE, buffer, 1);

Regards,

Linus

[mschweig]

Hi, thanks!