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痛斥 AT 之 AT 组件

发布于 2021-06-26 09:34:46 浏览：3133 订阅该版

最近本人重新使用了一下 AT 组件，阅读了其源码，并拓展阅读了一下 at_socket 及 at_device 的源码，深恶痛绝，特此写下该系列的吐槽文章。
首先我先展示下我的最终效果，我使用的 MCU 为 GD32，模组为 EC600S-CN。
我将每个 socket 都作为一个 device：
```
msh />list_device
device                   type         ref count
---------------- -------------------- ----------
norflash0        Block Device         0
spi20            SPI Device           0
rtc              RTC                  0
EC600S_skt11     Miscellaneous Device 0
EC600S_skt10     Miscellaneous Device 0
EC600S_skt9      Miscellaneous Device 0
EC600S_skt8      Miscellaneous Device 0
EC600S_skt7      Miscellaneous Device 0
EC600S_skt6      Miscellaneous Device 0
EC600S_skt5      Miscellaneous Device 0
EC600S_skt4      Miscellaneous Device 0
EC600S_skt3      Miscellaneous Device 1
EC600S_skt2      Miscellaneous Device 1
EC600S_skt1      Miscellaneous Device 1
EC600S_skt0      Miscellaneous Device 1
EC600S           Miscellaneous Device 1
spi2             SPI Bus              0
i2c1             I2C Bus              0
wdt              Miscellaneous Device 0
acon             Character Device     2
usart5           Character Device     0
usart2           Character Device     1
usart1           Character Device     1
pin              Miscellaneous Device 0
msh />lis
list_fd
list_thread
list_sem
list_event
list_mutex
list_mailbox
list_msgqueue
list_timer
list_device
msh />list_fd
fd type    ref magic  path
-- ------  --- ----- ------
 3 device    1 fdfd  /acon
 4 device    1 fdfd  /usart2
 5 device    1 fdfd  /EC600S_skt0
 6 device    1 fdfd  /EC600S_skt1
 7 device    1 fdfd  /EC600S_skt2
 8 device    1 fdfd  /EC600S_skt3
msh />

```
编程方法如下：
```C
rt_device_t ec600s_dev = rt_device_find(EC600S_DEVICE_NAME);
    rt_device_t empty_socket;
    rt_device_control(ec600s_dev, RT_EC600S_CTRL_ALLOC_SOCKET, &empty_socket);

char port[30] = "";
    strcat(port, "/dev/");
    strcat(port, empty_socket->parent.name);
    int s = open(port, O_RDWR);
    struct ec600s_socket_configure config;
    config.type = EC600S_SOCKET_TCP;
    config.server = "119.23.105.150";
    config.port = 6008;
    int rc;

fd_set rset, wset, errset;
    struct timeval select_timeout;

_tcp_pass_start:
    rc = ioctl(s, RT_EC600S_SOCKET_CTRL_CONNECT, &config);
    if(rc != 0)
        goto _tcp_pass_restart;
    
    select_timeout.tv_sec = 150;
    select_timeout.tv_usec = 0;

FD_ZERO(&wset);
    FD_SET(s, &wset);

rc = select(s + 1, RT_NULL, &wset, RT_NULL, &select_timeout);
    if(rc <= 0)
        goto _tcp_pass_restart;

rt_kprintf("TCP server connect success.\r\n");

select_timeout.tv_sec = 1;
    select_timeout.tv_usec = 0;

restart_flag = 0;

while(1)
    {
        if(restart_flag)
            break;
        
        FD_ZERO(&rset);
        FD_ZERO(&errset);
        FD_SET(s, &rset);
        FD_SET(s, &errset);
        rc = select(s + 1, &rset, RT_NULL, &errset, &select_timeout);
        if(rc < 0)
            break;
        if(rc > 0)
        {
            if(FD_ISSET(s, &errset))
                break;
            if(FD_ISSET(s, &rset))
            {
                int recv_len = tcp_receive(s, recv_buf, sizeof(recv_buf), 300, 300);
                if(recv_len <= 0)
                    break;
                LOG_I("recv len:%d", recv_len);
                if(write(s, recv_buf, recv_len) != recv_len)
                    break;
            }
        }
    }

_tcp_pass_restart:
    ioctl(s, RT_EC600S_SOCKET_CTRL_CLOSE, RT_NULL);
    rt_thread_mdelay(1000);
    rt_kprintf("restart!\r\n");
    goto _tcp_pass_start;
```
使用 posix 接口对每个 socket 进行操作。
最终测试结果：
![image.png](https://oss-club.rt-thread.org/uploads/20210626/c4f111413214ead099f17eb80c424382.png)
使用 4 个 socket 连接服务器，这里我使用了内网穿透。
通过服务器给 4 个 socket 同时发送 1000K 的数据。

1.at_client 的 end sign
设置 end sign 就是需要到结束符的时候通知应用啊，at_client 中检测到 end sign 就作为一行，然后呢也没个通知，怎么用？
我们来看下 at_device 中对于其的使用：
        
![image.png](https://oss-club.rt-thread.org/uploads/20210626/402d9215dce847bb2fc26ea4290fe253.png)

创建 resp 的时候指定行数为 2，设置 end sign 为 > ,这出问题概率不要太高。模组中间突然给你上报一条 URC ，你也认为满足条件了，然后就开始发送数据，结果就是出问题。

我的改进方案：
![image.png](https://oss-club.rt-thread.org/uploads/20210626/6884ab74cefd1b90bfbf04fd265d7f19.png)

增加 end sign 的通知。

2.at_client_obj_recv 的问题
```C
rt_size_t at_client_obj_recv(at_client_t client, char *buf, rt_size_t size, rt_int32_t timeout)
{
    rt_size_t read_idx = 0;
    rt_err_t result = RT_EOK;
    char ch;

RT_ASSERT(buf);

if (client == RT_NULL)
    {
        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
        return 0;
    }

while (1)
    {
        if (read_idx < size)
        {
            result = at_client_getchar(client, &ch, timeout);
            if (result != RT_EOK)
            {
                LOG_E("AT Client receive failed, uart device get data error(%d)", result);
                return 0;
            }

buf[read_idx++] = ch;
        }
        else
        {
            break;
        }
    }

#ifdef AT_PRINT_RAW_CMD
    at_print_raw_cmd("urc_recv", buf, size);
#endif

return read_idx;
}
```
你这一个字节一个字节获取，得多占用时间啊。而且一旦读取过程中有一个字节没获取到就返回 0 ，很有问题。
我的优化方案：
```C
rt_size_t at_client_obj_recv(at_client_t client, char *buf, rt_size_t size, rt_int32_t timeout)
{
    rt_size_t len = 0;

RT_ASSERT(buf);

if (client == RT_NULL)
    {
        LOG_E("input AT Client object is NULL, please create or get AT Client object!");
        return 0;
    }

while(1)
    {
        rt_sem_control(client->rx_notice, RT_IPC_CMD_RESET, RT_NULL);

rt_size_t read_len = rt_device_read(client->device, 0, buf + len, size);
        if(read_len > 0)
        {
            len += read_len;
            size -= read_len;
            if(size == 0)
                break;
            
            continue;
        }

if(rt_sem_take(client->rx_notice, rt_tick_from_millisecond(timeout)) != RT_EOK)
            break;
    }

#ifdef AT_PRINT_RAW_CMD
    at_print_raw_cmd("urc_recv", buf, len);
#endif

return len;
}
```