China Mobile 4G module-ML302-OpenCpu development-(MQTT connection to Alibaba Cloud-receiving and sending data)

Station B: https://space.bilibili.com/309103931

China Mobile 4G module-ML302 column: https://blog.csdn.net/qq_33259323/category_10453372.html

China Mobile 4G Module-ML302 Collection: https://www.bilibili.com/read/readlist/rl328642

1. China Mobile 4G module-ML302-OpenCpu development-(firmware compilation and burning)

https://blog.csdn.net/qq_33259323/article/details/108586847

https://www.bilibili.com/read/cv7876504

2. China Mobile 4G module-ML302-OpenCpu development-(MQTT connects to Alibaba Cloud)

https://blog.csdn.net/qq_33259323/article/details/108638945

https://www.bilibili.com/read/cv7876527

2.1 China Mobile 4G module-ML302-OpenCpu development-(MQTT connection to Alibaba Cloud-subscribe topic)

https://blog.csdn.net/qq_33259323/article/details/108960540

https://www.bilibili.com/read/cv7879954

2.2 China Mobile 4G module-ML302-OpenCpu development-(MQTT connection to Alibaba Cloud-receiving and sending data)

https://blog.csdn.net/qq_33259323/article/details/108964810

https://www.bilibili.com/read/cv7886836

2.3 China Mobile 4G Module-ML302-OpenCpu Development-(MQTT connects to Alibaba Cloud-RRPC communication)

https://blog.csdn.net/qq_33259323/article/details/108965071

https://www.bilibili.com/read/cv7888259

3. China Mobile 4G module-ML302-OpenCpu development-serial port development

https://blog.csdn.net/qq_33259323/article/details/108974888

https://www.bilibili.com/read/cv7888865

4. China Mobile 4G module-ML302-OpenCpu development-51 MCU serial port to I2C

https://blog.csdn.net/qq_33259323/article/details/109020642

https://www.bilibili.com/read/cv7922942

5. China Mobile 4G module-ML302-OpenCpu development-MCP23017 input/output

https://blog.csdn.net/qq_33259323/article/details/109109136

https://www.bilibili.com/read/cv7969395

7. Mid-shift 4G module-ML302-OpenCpu development-PCF8591 measurement voltage

https://blog.csdn.net/qq_33259323/article/details/109109266

https://www.bilibili.com/read/cv7969365

8. China Mobile 4G module-ML302-OpenCpu development-GPIO

https://blog.csdn.net/qq_33259323/article/details/108960947

https://www.bilibili.com/read/cv7877192

9. China Mobile 4G Module-ML302-OpenCpu Development-ADC

https://blog.csdn.net/qq_33259323/article/details/109020864

https://www.bilibili.com/read/cv7922958

10. China Mobile 4G Module-ML302-OpenCpu Development-CJSON

https://blog.csdn.net/qq_33259323/article/details/109020898

https://www.bilibili.com/read/cv7923020

11. China Mobile 4G Module-ML302-OpenCpu Development-HTTP

https://blog.csdn.net/qq_33259323/article/details/109020904

https://www.bilibili.com/read/cv7923054

China Mobile 4G module-ML302-OpenCpu development-(MQTT connection to Alibaba Cloud-receiving and sending data)

According to the study in the previous article, if you haven’t read it, you can take a look at the above 2.1 China Mobile 4G module-ML302-OpenCpu development-(MQTT connection to Alibaba Cloud-subscribe topic)

The data can be received, how to send it.

int example_publish(void *handle)
{
    int             res = 0;
    const char     *fmt = "/%s/%s/user/get";
    char           *topic = NULL;
    int             topic_len = 0;
    char           *payload = "{\"message\":\"hello!\"}";

    //*** 对topic的拼接***

    topic_len = strlen(fmt) + strlen(DEMO_PRODUCT_KEY) + strlen(DEMO_DEVICE_NAME) + 1;
    topic = HAL_Malloc(topic_len);
    if (topic == NULL) {
        cm_printf("[ALIYUN]: memory not enough\n");  
        return -1;
    }
    memset(topic, 0, topic_len);
    HAL_Snprintf(topic, topic_len, fmt, DEMO_PRODUCT_KEY, DEMO_DEVICE_NAME);

    //*** 对topic的拼接***
    
    // 调用IOT_MQTT_Publish_Simple发送数据
    res = IOT_MQTT_Publish_Simple(0, topic, IOTX_MQTT_QOS0, payload, strlen(payload));
    
    if (res < 0) {
        cm_printf("[ALIYUN]: publish failed, res = %d\n", res);
        HAL_Free(topic);
        return -1;
    }

    HAL_Free(topic);
    return 0;
}

IOT_MQTT_Publish_Simple function

topic_name: topic name

qos:qos

data: data

len: send data length

int IOT_MQTT_Publish_Simple(void *handle, const char *topic_name, int qos, void *data, int len)

This is a relatively simple MQTT sending program