Publishing MQTT data to multiple topics in Thingy91

RE: Publishing MQTT data to multiple topics in Thingy91

Adeel — Wed, 10 Feb 2021 09:59:40 GMT

Hi Hakon,

Yes, makes sense. I understood what you mean here. This helps 🙂.

Thanks for the help :) .

Regards,

Adeel.

RE: Publishing MQTT data to multiple topics in Thingy91

Hakon — Tue, 09 Feb 2021 14:06:16 GMT

[quote user="Adeel"]Is it possible to have just one data_publish function wherein I can publish to various topics ?[/quote]

Yes, it should be possible to use the same function if you just change the content of param.message.topic.topic.utf8 between each time you call mqtt_publish(). No need to have two separate functions, just change the publish topic inside the data_publish() function. Does that make sense?

RE: Publishing MQTT data to multiple topics in Thingy91

Adeel — Wed, 03 Feb 2021 12:54:19 GMT

Hi Hakon,

[quote userid="73166" url="~/f/nordic-q-a/70951/publishing-mqtt-data-to-multiple-topics-in-thingy91/292670#292670"] You can't use the data_publish() as it is, because the publish topic is hard coded.[/quote]

Yeah I understand this now.

I added another function : data_publish1() like this :

/**@brief Function to publish data on the configured topic
 */
static int data_publish(struct mqtt_client *c, enum mqtt_qos qos,
	u8_t *data, size_t len)
{
	struct mqtt_publish_param param;

	param.message.topic.qos = qos;
	param.message.topic.topic.utf8 = CONFIG_MQTT_PUB_TOPIC;
	param.message.topic.topic.size = strlen(CONFIG_MQTT_PUB_TOPIC);
	param.message.payload.data = data;
	param.message.payload.len = len;
	param.message_id = sys_rand32_get();
	param.dup_flag = 0;
	param.retain_flag = 0;

	data_print("Publishing: ", data, len);
	printk("to topic: %s len: %u\n",
		CONFIG_MQTT_PUB_TOPIC,
		(unsigned int)strlen(CONFIG_MQTT_PUB_TOPIC));

	return mqtt_publish(c, &param);
}


/**@brief Function to publish data on the configured topic
 */
static int data_publish1(struct mqtt_client *c, enum mqtt_qos qos,
	u8_t *data, size_t len)
{
	struct mqtt_publish_param param;

	param.message.topic.qos = qos;
	param.message.topic.topic.utf8 = CONFIG_MQTT_PUB_TOPIC_1;
	param.message.topic.topic.size = strlen(CONFIG_MQTT_PUB_TOPIC_1);
	param.message.payload.data = data;
	param.message.payload.len = len;
	param.message_id = sys_rand32_get();
	param.dup_flag = 0;
	param.retain_flag = 0;

	data_print("Publishing: ", data, len);
	printk("to topic: %s len: %u\n",
		CONFIG_MQTT_PUB_TOPIC_1,
		(unsigned int)strlen(CONFIG_MQTT_PUB_TOPIC_1));

	return mqtt_publish(c, &param);
}

In the autoconf.h file, I added :

#define CONFIG_MQTT_PUB_TOPIC "sensorstest1/nrf352656101119801/pressure"
#define CONFIG_MQTT_PUB_TOPIC_1 "sensorstest1/nrf352656101119801/humidity"

In the MQTT_EVENT_PUBLISH: , i added :

case MQTT_EVT_PUBLISH: {
		const struct mqtt_publish_param *p = &evt->param.publish;

		printk("[%s:%d] MQTT PUBLISH result=%d len=%d\n", __func__,
		       __LINE__, evt->result, p->message.payload.len);
		err = publish_get_payload(c, p->message.payload.len);
		if (err >= 0) {
			data_print("Received: ", payload_buf,
				p->message.payload.len);
			/* Echo back received data */
			data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE,
				payload_buf, p->message.payload.len);
                        data_publish1(&client, MQTT_QOS_1_AT_LEAST_ONCE,
				payload_buf, p->message.payload.len);

This made it work as I am able to publish on different topic.

Is it possible to have just one data_publish function wherein I can publish to various topics ? (only if possible, otherwise the above mentioned method is working :) ).

Regards,

Adeel.

RE: Publishing MQTT data to multiple topics in Thingy91

Hakon — Wed, 03 Feb 2021 12:46:51 GMT

[quote user="Adeel"]Could you let me know if there can be another method for doing this ?[/quote]

You can't use the data_publish() as it is, because the publish topic is hard coded. But you can just change the value of param.message.topic.topic.utf8 to something else.

RE: Publishing MQTT data to multiple topics in Thingy91

Adeel — Mon, 01 Feb 2021 10:28:36 GMT

Hi Hakon,

I found a way of doing this, though I am not sure its the most optimized way.

I duplicated the data_publish() function in the mqtt_simple , with a name : data_publish1() and configured it with a different topic : CONFIG_MQTT_PUB_TOPIC_1. I already updated this topic in the autoconf.h file.

I added this new function I created to the MQTT_EVT_PUBLISH event after the data_publish() function.

By doing this, I am able to publish different data to different topics now, although I think there can be an optimized method of doing this instead of creating new functions for different MQTT_topics.

Could you let me know if there can be another method for doing this ?

Regards,

Adeel.

RE: Publishing MQTT data to multiple topics in Thingy91

Adeel — Thu, 28 Jan 2021 10:07:14 GMT

Hi Hakon,

No, I am just building up my application on the mqtt_simple example. So basically the sample I am using is mqtt_simple.

Right now, I have 1 topic assigned and I am able to publish the data to that topic. I need to publish another data to a different topic as well. I wanted to know as to how I could do that.

Regards,

Adeel.

RE: Publishing MQTT data to multiple topics in Thingy91

Hakon — Thu, 28 Jan 2021 10:04:36 GMT

What sample are you using? Are you using the AWS IoT library?

RE: Publishing MQTT data to multiple topics in Thingy91

Adeel — Thu, 28 Jan 2021 09:56:30 GMT

Hi Hakon,

I meant publishing to multiple topics .

Regards,

Adeel.

RE: Publishing MQTT data to multiple topics in Thingy91

Hakon — Thu, 28 Jan 2021 09:54:50 GMT

Hello,

[quote user=""]Could you let me know how to configure multiple topics in the program ?[/quote]

What do you mean by configure multiple topics? Do you mean publishing to multiple topics or subscribe to multiple topics?