通过SIM800C与onenet进行数据传输例程（基于STM32F407）

以下是基于STM32F407和SIM800C模块通过onenet进行数据传输的例程：

首先，需要连接SIM800C模块和STM32F407开发板。连接方式如下：

SIM800C模块：

VCC：5V
GND：GND
RXD：PA9
TXD：PA10
PWRKEY：PB0
RESET：PB1

STM32F407开发板：

PA9：SIM800C的RXD
PA10：SIM800C的TXD
PB0：SIM800C的PWRKEY
PB1：SIM800C的RESET

在STM32F407开发板上使用HAL库进行编程，首先需要配置UART串口：

/*定义串口句柄*/
UART_HandleTypeDef huart1;

/*初始化串口1*/
void MX_USART1_UART_Init(void)
{
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
}

接下来，需要配置SIM800C模块的AT指令：

/*定义AT指令缓存*/
char at_cmd[50];

/*发送AT指令*/
void send_at_cmd(char *cmd)
{
    HAL_UART_Transmit(&huart1, (uint8_t*)cmd, strlen(cmd), 1000);
    HAL_UART_Transmit(&huart1, (uint8_t*)"\r\n", 2, 1000);
}

/*获取AT指令回复*/
void get_at_reply(char *reply, uint16_t timeout)
{
    uint8_t rx_data;
    uint16_t idx = 0;
    HAL_UART_Receive(&huart1, &rx_data, 1, 0xFFFF);
    while (rx_data != '\n' && idx < 50)
    {
        if (rx_data != '\r')
        {
            reply[idx++] = rx_data;
        }
        HAL_UART_Receive(&huart1, &rx_data, 1, timeout);
    }
    reply[idx] = '\0';
}

接下来，需要连接onenet平台。首先需要获取设备ID和API Key：

/*定义设备ID和API Key*/
char device_id[] = "123456";
char api_key[] = "abcdefghijklmnopqrstuvwxyz";

然后，需要连接GPRS网络并获取IP地址：

/*连接GPRS网络*/
send_at_cmd("AT+CGATT=1");
get_at_reply(at_cmd, 1000);
send_at_cmd("AT+CSTT=\"CMNET\"");
get_at_reply(at_cmd, 1000);
send_at_cmd("AT+CIICR");
get_at_reply(at_cmd, 10000);

/*获取IP地址*/
send_at_cmd("AT+CIFSR");
get_at_reply(at_cmd, 1000);

接下来，需要连接onenet平台：

/*连接onenet平台*/
sprintf(at_cmd, "AT+CIPSTART=\"TCP\",\"%s\",\"%s\"", "183.230.40.39", "80");
send_at_cmd(at_cmd);
get_at_reply(at_cmd, 10000);

然后，需要构建HTTP请求头：

/*构建HTTP请求头*/
sprintf(at_cmd, "POST /devices/%s/datapoints HTTP/1.1\r\n", device_id);
send_at_cmd(at_cmd);
send_at_cmd("Host: api.heclouds.com\r\n");
sprintf(at_cmd, "api-key: %s\r\n", api_key);
send_at_cmd(at_cmd);
send_at_cmd("Content-Type: application/json\r\n");

接下来，需要构建HTTP请求体：

/*构建HTTP请求体*/
char json_data[50];
sprintf(json_data, "{\"datastreams\":[{\"id\":\"temperature\",\"datapoints\":[{\"value\":%d}]}]}", temperature);
sprintf(at_cmd, "Content-Length: %d\r\n", strlen(json_data));
send_at_cmd(at_cmd);
send_at_cmd("\r\n");
send_at_cmd(json_data);

最后，需要关闭GPRS网络和释放SIM800C模块的UART资源：

/*关闭GPRS网络*/
send_at_cmd("AT+CIPSHUT");
get_at_reply(at_cmd, 10000);

/*释放UART资源*/
HAL_UART_DeInit(&huart1);

完整的代码如下：

#include "main.h"
#include <string.h>
#include <stdio.h>

/*定义串口句柄*/
UART_HandleTypeDef huart1;

/*定义AT指令缓存*/
char at_cmd[50];

/*定义设备ID和API Key*/
char device_id[] = "123456";
char api_key[] = "abcdefghijklmnopqrstuvwxyz";

/*获取AT指令回复*/
void get_at_reply(char *reply, uint16_t timeout)
{
    uint8_t rx_data;
    uint16_t idx = 0;
    HAL_UART_Receive(&huart1, &rx_data, 1, 0xFFFF);
    while (rx_data != '\n' && idx < 50)
    {
        if (rx_data != '\r')
        {
            reply[idx++] = rx_data;
        }
        HAL_UART_Receive(&huart1, &rx_data, 1, timeout);
    }
    reply[idx] = '\0';
}

/*发送AT指令*/
void send_at_cmd(char *cmd)
{
    HAL_UART_Transmit(&huart1, (uint8_t*)cmd, strlen(cmd), 1000);
    HAL_UART_Transmit(&huart1, (uint8_t*)"\r\n", 2, 1000);
}

/*连接GPRS网络并获取IP地址*/
void connect_gprs_network()
{
    /*连接GPRS网络*/
    send_at_cmd("AT+CGATT=1");
    get_at_reply(at_cmd, 1000);
    send_at_cmd("AT+CSTT=\"CMNET\"");
    get_at_reply(at_cmd, 1000);
    send_at_cmd("AT+CIICR");
    get_at_reply(at_cmd, 10000);

    /*获取IP地址*/
    send_at_cmd("AT+CIFSR");
    get_at_reply(at_cmd, 1000);
}

/*连接onenet平台*/
void connect_onenet_platform()
{
    /*连接onenet平台*/
    sprintf(at_cmd, "AT+CIPSTART=\"TCP\",\"%s\",\"%s\"", "183.230.40.39", "80");
    send_at_cmd(at_cmd);
    get_at_reply(at_cmd, 10000);
}

/*构建HTTP请求头*/
void construct_http_request_header()
{
    /*构建HTTP请求头*/
    sprintf(at_cmd, "POST /devices/%s/datapoints HTTP/1.1\r\n", device_id);
    send_at_cmd(at_cmd);
    send_at_cmd("Host: api.heclouds.com\r\n");
    sprintf(at_cmd, "api-key: %s\r\n", api_key);
    send_at_cmd(at_cmd);
    send_at_cmd("Content-Type: application/json\r\n");
}

/*构建HTTP请求体*/
void construct_http_request_body(int temperature)
{
    /*构建HTTP请求体*/
    char json_data[50];
    sprintf(json_data, "{\"datastreams\":[{\"id\":\"temperature\",\"datapoints\":[{\"value\":%d}]}]}", temperature);
    sprintf(at_cmd, "Content-Length: %d\r\n", strlen(json_data));
    send_at_cmd(at_cmd);
    send_at_cmd("\r\n");
    send_at_cmd(json_data);
}

/*关闭GPRS网络*/
void shutdown_gprs_network()
{
    /*关闭GPRS网络*/
    send_at_cmd("AT+CIPSHUT");
    get_at_reply(at_cmd, 10000);
}

/*释放UART资源*/
void release_uart_resources()
{
    /*释放UART资源*/
    HAL_UART_DeInit(&huart1);
}

/*初始化串口1*/
void MX_USART1_UART_Init(void)
{
  huart1.Instance = USART1;
  huart1.Init.BaudRate = 115200;
  huart1.Init.WordLength = UART_WORDLENGTH_8B;
  huart1.Init.StopBits = UART_STOPBITS_1;
  huart1.Init.Parity = UART_PARITY_NONE;
  huart1.Init.Mode = UART_MODE_TX_RX;
  huart1.Init.HwFlowCtl = UART_HWCONTROL_NONE;
  huart1.Init.OverSampling = UART_OVERSAMPLING_16;
  if (HAL_UART_Init(&huart1) != HAL_OK)
  {
    Error_Handler();
  }
}

int main(void)
{
  /*初始化串口1*/
  MX_USART1_UART_Init();

  /*连接GPRS网络并获取IP地址*/
  connect_gprs_network();

  /*连接onenet平台*/
  connect_onenet_platform();

  /*构建HTTP请求头*/
  construct_http_request_header();

  /*构建HTTP请求体*/
  int temperature = 25;
  construct_http_request_body(temperature);

  /*关闭GPRS网络*/
  shutdown_gprs_network();

  /*释放UART资源*/
  release_uart_resources();

  while (1)
  {
  }
}