#开发板漂流计划#小车控制由简入繁之UDP控制原创精华

Soon_L

发布于 2021-10-5 16:17

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1.简介

在#开发板漂流计划#小车控制由简入繁之按键控制的基础上，实现小车上电后自动连接到指定WIFI，并建立UDP Server监听指定端口数据。电脑端作为UDP Client 连接到小车对应的端口，通过发送字符串来控制小车状态。
以下代码基于OpenHarmony-v3.0-LTS编译测试。

2.WIFI连接的实现

wifi连接的代码使用了润和Gitee中的wifi_connecter.c和wifi_connecter.h将这两个文件分别放到car目录下的src和include中，修改Car 目录下BUILD.gn和car_main.c添加如下代码，详细修改说明如下：

2.1.在applications\sample\wifi-iot\app\car\BUILD.gn中添加sources中添加编译wifi_connecter.c

static_library("car") {
    sources = [
        ......
        "src/wifi_connecter.c",
    ]

}

2.2.在applications\sample\wifi-iot\app\car\BUILD.gn中include_dirs 里面添加//applications/sample/wifi-iot/app/car/include这样wifi_connecter.h等就可以包到了，另外因为wifi_connecter.h中有用到wifi_device.h所以需要再把//foundation/communication/wifi_lite/interfaces/wifiservice加入。wifi_connecter.h中的"lwip/netifapi.h"和 “lwip/api_shell.h” 是在"//device/hisilicon/hispark_pegasus/sdk_liteos/third_party/lwip_sack/include"中也需要，所以需要添加以下路径。

    include_dirs = [
        ......
        "//applications/sample/wifi-iot/app/car/include",
        "//foundation/communication/wifi_lite/interfaces/wifiservice",
        "//device/hisilicon/hispark_pegasus/sdk_liteos/third_party/lwip_sack/include",
    ]

2.3 在car_main.c中参考如下修改,将wifi_connecter.h加入include，"SSIDABCD"改成你要连接的WIFI SSID， "MIMA1234"填入WIFI密码。

#include "wifi_connecter.h"
......
static void CarDemoTask(void *arg)
{
    ......

    // setup your AP params
    WifiDeviceConfig apConfig = {0};
    strcpy(apConfig.ssid, "SSIDABCD");
    strcpy(apConfig.preSharedKey, "MIMA1234");
    apConfig.securityType = WIFI_SEC_TYPE_PSK;
    int netId = ConnectToHotspot(&apConfig);
    printf("[CarDemo] ConnectToHotspot done netId=%d!\n",netId);

}

securityType 的enum 如下按照你的WIFI设定的加密方式来选择，

typedef enum {
    /** Invalid security type */
    WIFI_SEC_TYPE_INVALID = -1,
    /** Open */
    WIFI_SEC_TYPE_OPEN,
    /** Wired Equivalent Privacy (WEP) */
    WIFI_SEC_TYPE_WEP,
    /** Pre-shared key (PSK) */
    WIFI_SEC_TYPE_PSK,
    /** Simultaneous Authentication of Equals (SAE) */
    WIFI_SEC_TYPE_SAE,
} WifiSecurityType;

通过ConnectToHotspot()就可以轻松的连接到指定WIFI了。

3.UDP Server的实现
3.1 UDP Server的实现代码
在hispark_pegasus中可以使用"//device/hisilicon/hispark_pegasus/sdk_liteos/third_party/lwip_sack/include"（该目录在WIFI连接的实现中已添加）中的"lwip/sockets.h"来实现，代码如下

#include "lwip/sockets.h"

static char response[] = "\nSucess.\n";
static char message[128] = "";
void UdpServer(unsigned short port)
{
    ssize_t retval = 0;
    int needfb = 0;
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0); // UDP socket

    struct sockaddr_in clientAddr = {0};
    socklen_t clientAddrLen = sizeof(clientAddr);
    struct sockaddr_in serverAddr = {0};
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(port);
    serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    retval = bind(sockfd, (struct sockaddr *)&serverAddr, sizeof(serverAddr));
    if (retval < 0) {
        printf("bind failed, %ld!\r\n", retval);
        goto do_cleanup;
    }
    printf("bind to port %d success!\r\n", port);

    while(1)
    {
        needfb = 0;
        memset(message, 0, sizeof(message));
        retval = recvfrom(sockfd, message, sizeof(message), 0, (struct sockaddr *)&clientAddr, &clientAddrLen);
        if (retval > 0) {
            printf("recv message {%s} %ld done!\r\n", message, retval);
            printf("peer info: ipaddr = %s, port = %d\r\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));

            if(strncmp("forward", message, 7)== 0) {
                needfb = 1;
                car_go_forward();
            }
            if(strncmp("back", message, 4) == 0) {
                needfb = 1;
                car_go_back();
            }
            if(strncmp("left", message, 4) == 0) {
                needfb = 1;
                car_turn_left();
            }
            if(strncmp("right", message, 5) == 0) {
                needfb = 1;
                car_turn_right();
            }
            if(strncmp("stop", message, 4) == 0) {
                needfb = 1;
                car_stop();
            }
            if(needfb == 1) {
                retval = sendto(sockfd, response, strlen(response), 0, (struct sockaddr *)&clientAddr, sizeof(clientAddr));
                if (retval > 0) {  
                    printf("send response {%s} %ld done!\r\n", response, retval);
                } else {
                    printf("send failed, %ld!\r\n", retval);
                }
            }
        }
    }

do_cleanup:
    printf("do_cleanup...\r\n");
    close(sockfd);
}

需要注意的是在每次检查数据recvfrom()前memset(message, 0, sizeof(message))清一下之前的数据。
在收到"forward"、“back”、“left”、“right”、“stop"后会执行相应的小车控制函数，并回复"Sucess”。
3.2 UDP Server的调用
在Task 最后面调用UdpServer()传入端口函数即可,这里端口使用62021

static void CarDemoTask(void *arg)
{
    ......
    UdpServer(62021);
    
    printf("[CarDemo] create CarDemoTask!\n");
}

4.编译
4.1 将附件car.zip 解压后放到applications\sample\wifi-iot\app\下，如下图
4.2 修改applications/sample/wifi-iot/app/BUILD.gn

import("//build/lite/config/component/lite_component.gni")

lite_component("app") {
    features = [
        "car",
    ]
}

4.3 电机的控制需要用到PWM，所以需要先将PWM 功能开启，开启方式如下
device/hisilicon/hispark_pegasus/sdk_liteos/build/config/usr_config.mk

# CONFIG_PWM_SUPPORT is not set

改为

CONFIG_PWM_SUPPORT=y

4.4 进入代码根目录执行hb set输入.(当前目录)并选择wifiiot_hispark_pegasus，执行 hb build -b release -f

soon@soon-u20:~/ohos300_iot $ hb set
[OHOS INFO] Input code path: .
OHOS Which product do you need?  wifiiot_hispark_pegasus
soon@soon-u20:~/ohos300_iot $ hb build -b release -f

4.5 使用HiBurn或者Visual Studio Code烧录，可参考
使用HiBurn烧录鸿蒙.bin文件到Hi3861开发板
5.功能测试
5.1 从串口日志获取小车IP，如下图成功连接WIFI获取IP 打印如下，如我这边获取的IP为192.168.123.247
5.2 电脑端测试软件如附件SocketTool2.zip ，解压后直接运行按下图步骤创建UDP Client，

建立连接后就可以在数据发送窗口中发送文本数据"forward"、“back”、“left”、“right”、"stop"来控制小车了，小车接受成功后回复Sucess如下图。
6.总结