Connect devices that do not have an operating system

Prerequisites

• You have obtained the C Link SDK.

• You are familiar with the C Link SDK porting interfaces.

• You have obtained the device certificate.

Step 1: Port the interfaces

The device can run properly only after you implement the underlying interfaces that the Link SDK depends on. The following table describes how to implement different interfaces.

Step 2: Develop the application

For devices with an operating system, you can use multitasking in your application because the interfaces are blocking and a single task can affect other operations. Devices without an operating system have only one task. To handle blocking interfaces in the Link SDK, you can reduce the blocking time to minimize the impact on your business logic.

Blocking interfaces in the MQTT module

Configure the timeout period

    /* Configure the MQTT timeout period. */
    int32_t recv_timeout = 1000, connect_timeout = 2000;
    aiot_mqtt_setopt(mqtt_handle, AIOT_MQTTOPT_RECV_TIMEOUT_MS, (void *)&recv_timeout);
    aiot_mqtt_setopt(mqtt_handle, AIOT_MQTTOPT_CONNECT_TIMEOUT_MS, (void *)&connect_timeout);

Example

Environment description

Porting implementation example

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include "os_net_interface.h"
#include "stm32l4xx_hal.h"

/**
 * @brief Obtains the current timestamp. The SDK uses it to calculate differences.
 */
uint64_t __time(void) {
    return (uint64_t)HAL_GetTick();
}
/**
 * @brief Sleeps for the specified number of milliseconds.
 */
void __sleep(uint64_t time_ms) {
	  uint64_t start = __time();
	  while(__time() - start < time_ms) {
			;
		}
}
/**
 * @brief Method for random number generation.
 */
void __rand(uint8_t *output, uint32_t output_len) {
    uint32_t idx = 0, bytes = 0, rand_num = 0;

    srand(__time());
    for (idx = 0; idx < output_len;) {
        if (output_len - idx < 4) {
            bytes = output_len - idx;
        } else {
            bytes = 4;
        }
        rand_num = rand();
        while (bytes-- > 0) {
            output[idx++] = (uint8_t)(rand_num >> bytes * 8);
        }
    }
}
/**
 * @brief Creates a mutex.
 */
void*  __mutex_init(void) {
    return (void *)0xFFFFFFFF;
}
/**
 * @brief Locks a mutex.
 */
void __mutex_lock(void *mutex) {
    
}
/**
 * @brief Unlocks a mutex.
 */
void __mutex_unlock(void *mutex) {

}
/**
 * @brief Destroys a mutex.
 */
void __mutex_deinit(void **mutex) {
    if (mutex == NULL || *mutex == NULL) {
        return;
    }
    *mutex = NULL;
}

aiot_os_al_t  g_aiot_freertos_api = {
    .malloc = malloc,
    .free = free,
    .time = __time,
    .sleep = __sleep,
    .rand = __rand,
    .mutex_init = __mutex_init,
    .mutex_lock = __mutex_lock,
    .mutex_unlock = __mutex_unlock,
    .mutex_deinit = __mutex_deinit,
};

Example project

1. Download the example project.

2. You can use MDK-Arm to open the project at ./LinkSDK/portfiles/aiot_port/project/stm32_noneos/MDK-ARM/L476.uvprojx.

   For more information about how to use MDK-Arm, see MDK-Arm.

3. To adapt the interfaces for different environments, you can modify the ./LinkSDK/portfiles/aiot-port/project/stm32_noneos/Core/os_none_impl.c file.

   For more information about how to modify the file, see Step 1: Port the interfaces.

4. You can open ./LinkSDK/portfiles/aiot-port/project/stm32_noneos/Core/mqtt_at_basic_demo.c and configure the device certificate.

   Parameter	Example	Description
   product_key	a18wP******	The device certificate information. This is the device certificate that you obtained during preparation. You can also view the device certificate on the device details page in the IoT Platform console.
   device_name	LightSwitch
   device_secret	uwMTmVA**********DY6cHxxB******
   mqtt_host	a18wP******.iot-as-mqtt.cn-shanghai.aliyuncs.com	The MQTT domain name for device access. For the domain names of public instances and Enterprise instances, see View instance endpoints.

5. You can compile the project files and then download the executable file to the development board to run it.

   • After the file runs successfully, you can view logs on the device.

     • Module initialization:

       >>> AT
       >>> AT
       <<<
       RDY
       >>> AT
       <<< AT
       OK
       >>> AT+QIACT=1
       <<<
       OK
       >>> AT+QIACT?
       <<<
       +QIACT: 1,1,1,"10.13.***.***"
       OK

     • Establish a connection:

       [22.400][LK-0313] MQTT user calls aiot_mqtt_connect api, connect
       [22.433][LK-0317] LightSwitch&a18wP******
       [22.444][LK-0318] B4C45425D73E24B2935D73C1E98B6079A630FBE03F61E2A2031CEE7867D4D0D7
       >>> AT+QIOPEN=1,1,"TCP","a18wP******.iot-as-mqtt.cn-shanghai.aliyuncs.com",443,0,1
       <<<
       OK
       <<<
       +QIOPEN: 1,0
       >>> AT+QISEND=1,286
       <<<
       > >>> <<<
       SEND OK
       <<<
       +QIURC: "recv",1,4
        id 0, len 4, res 20
       [22.744][LK-0313] MQTT connect success in 341 ms
       AIOT_MQTTEVT_CONNECT

     • Report data:

       [27.766][LK-0309] pub: /sys/a18wP******/LightSwitch/thing/event/property/post
       [LK-030A] > 7B 22 69 64 22 3A 22 31  22 2C 22 76 65 72 73 69 | {"id":"1","versi
       [LK-030A] > 6F 6E 22 3A 22 31 2E 30  22 2C 22 70 61 72 61 6D | on":"1.0","param
       [LK-030A] > 73 22 3A 7B 22 4C 69 67  68 74 53 77 69 74 63 68 | s":{"LightSwitch
       [LK-030A] > 22 3A 30 7D 7D                                   | ":0}}
       >>> AT+QISEND=1,120
       <<<
       > >>> 0v<<<
       SEND OK
       <<<
       +QIURC: "recv",1,178
       0?id 0, len 178, res 22

     • Receive data:

       [27.933][LK-0309] pub: /sys/a18wP******/LightSwitch/thing/event/property/post_reply
       [LK-030A] < 7B 22 63 6F 64 65 22 3A  32 30 30 2C 22 64 61 74 | {"code":200,"dat
       [LK-030A] < 61 22 3A 7B 7D 2C 22 69  64 22 3A 22 31 22 2C 22 | a":{},"id":"1","
       [LK-030A] < 6D 65 73 73 61 67 65 22  3A 22 73 75 63 63 65 73 | message":"succes
       [LK-030A] < 73 22 2C 22 6D 65 74 68  6F 64 22 3A 22 74 68 69 | s","method":"thi
       [LK-030A] < 6E 67 2E 65 76 65 6E 74  2E 70 72 6F 70 65 72 74 | ng.event.propert
       [LK-030A] < 79 2E 70 6F 73 74 22 2C  22 76 65 72 73 69 6F 6E | y.post","version
       [LK-030A] < 22 3A 22 31 2E 30 22 7D                          | ":"1.0"}
       pub, qos: 0, topic: /sys/a18wP******/LightSwitch/thing/event/property/post_reply

   • You can also view logs in the IoT Platform console. For more information, see IoT Platform logs.