nrf 9160 Serial MQTT

Question

Hello All, 
 I am trying to send data on serial port of nrf9160 to be published on a topic using MQTT protocol. So far using the mqtt example and UART example, I have successfully run both code independently not with each other . I am not sure how to integrate the UART received buffer in the publish function so that I could send the data to the broker on that specific topic. Can some please help me out with this. I would really appreciate it. 
 The following are the modifications which I have added to the main code: 1. function to respond on serial event static u8_t uart_buf[1024];
int i=0;
static u8_t inData[20];
void uart_cb(struct device *x)
{
	uart_irq_update(x);
	int data_length = 0;

	if (uart_irq_rx_ready(x)) {
 data_length = uart_fifo_read(x, uart_buf, sizeof(uart_buf));
 uart_buf[data_length] = 0;
	}

 if(i==19 || *uart_buf == '?'){ 
 inData[i] = '\0';
 printk("%s
",inData);
 i=0;
 }
 else{
 memcpy(&inData[i], uart_buf, 1); 
 i++;
 }
} 
 
 2. In the main function I have added this struct device *uart = device_get_binding("UART_0");

	uart_irq_callback_set(uart, uart_cb);
	uart_irq_rx_enable(uart);
	printk("UART loopback start!
"); 
 4. The following code has modifications. It takes data from serial port "uart_buf" and then publish it. I have made minor changes to length and some changes to if statement so that it publishes directly case MQTT_EVT_PUBLISH: {
 const struct mqtt_publish_param *p = &evt->param.publish;

 printk("[%s:%d] MQTT PUBLISH result=%d len=%d
", __func__,
 __LINE__, evt->result, p->message.payload.len);
 err = publish_get_payload(c, p->message.payload.len);
 if (err >= 0) { // just for testing
 data_print("Received: ", uart_buf,
 strlen(uart_buf));
 /* Echo back received data */
 data_publish(&client, MQTT_QOS_1_AT_LEAST_ONCE,
 uart_buf, strlen(uart_buf));
 } else {
 printk("mqtt_read_publish_payload: Failed! %d
", err);
 printk("Disconnecting MQTT client...
");

 err = mqtt_disconnect(c);
 if (err) {
 printk("Could not disconnect: %d
", err);
 }
 }
	} break; It doesn't seem to work. Can some please help me out with the same

Simon · Accepted Answer

The sample works in the following manner 
 
 Several work items are initialized: 
 
 for(int i=0; i < SERIAL_Q_SIZE; i++){
 k_work_init(&w_data[i].work, pub_uart_mqtt);
} 
 
 Serial data is sent from the computer to nRF9160 through a micro USB and uart_cb() gets called 
 In uart_cb() the incoming serial data is processed and put into the queue (at the top of main.c I have created an array of static struct work_data of size 5) 
 Each incoming element (separated by 10 (=LF)) is submitted to the work queue through k_work_submit() 
 When the work queue Thread gets scheduled to run, it will call pub_uart_mqtt() for each element, where the elements will be published to the topic CONFIG_MQTT_PUB_TOPIC through data_publish()

Try following these steps: 
 
 Put the sample into NCS of version 1.1.0 in the following folder: ncs
rf\samples
rf9160 
 Download and install Mosquitto on your computer: https://mosquitto.org/download/ 
 
 Add the Mosquitto folder to the System Variables path : C:\Program Files\Mosquitto

Make sure the following are set in prj.conf: 
 
 CONFIG_MQTT_PUB_TOPIC="/my/publish/topic"
CONFIG_MQTT_SUB_TOPIC="/my/subscribe/topic"
CONFIG_MQTT_CLIENT_ID="my-client-id"
CONFIG_MQTT_BROKER_HOSTNAME="mqtt.eclipse.org"
CONFIG_MQTT_BROKER_PORT=1883 
 
 Build and run the sample 
 
 west build -b nrf9160_pca10090ns 
 nrfjprog --eraseall 
 west flash

Subscribe to the topic /my/publish/topic -v from the mosquitto broker, by typing the following in a command line (cmd, git bash etc..) 
 
 mosquitto_sub -h mqtt.eclipse.org -t /my/publish/topic -v

Open Tera Term with the following setup:

Then, in Tera Term, type in e.g. "Hey", followed by enter and you should see the following response in the command line where mosquitto_sub -h were called 
 
 C:\Users\Simon>mosquitto_sub -h mqtt.eclipse.org -t /my/publish/topic -v
/my/publish/topic Hey

nrf 9160 Serial MQTT

Top Replies