[嵌入式]RT-Thread AT组件对接Modem RIL xMUX的AT接口的方法

前言

• RT-Thread 的AT组件，可以用于对接基于串口的蜂窝模块，如SIM800这样的模块，实现电话与短信等业务
• 目前部分蜂窝厂商，提供的Modem芯片，可能不是uart串口，而是SPI、USB或其他串口，他们提供了xMUX多路复用的组件，也就说，底层可以提供一个类uart的AT收发接口。
• 如何使用AT组件对接这种xMUX出来的AT收发接口呢？如物理上是SPI接口，通过xMUX出来几个接口，包括数据服务与AT命令的接口。

解决方法

• 这时，需要手动注册一个基于RT-Thread rt_device 字符设备，因为AT组件，就是通过字符设备，对底层进行AT命令的收发控制的。
• 如何注册这样的设备？我开个BSP_USING_UART？不用，这个字符设备不是具体的外设的接口设备，只是一个字符设备即可。
• 上一篇我们讲过把一个引脚（LED）抽象成一个设备，本篇就用这个方法，改改名字，抽象一个ril设备出来，用于对接Modem xMUX的AT命令接口。
• 后续可以根据这个思路，抽象一个【虚拟网卡】设备出来，用于对接Modem xMUX的【数据服务】接口。

操作步骤

• 验证平台：STM32L475 Pandora 开发板
• board\Kconfig配置，用于控制是否开启设备，这里使用RIL_VDEVICE命名。

    config BSP_USING_RIL_VDEVICE
        bool "Enable RIL Virtual Device"
        default n
    if BSP_USING_RIL_VDEVICE
        config BSP_RIL_VDEVICE_NAME
        string "RIL Virtual Device Name"
        default "ril_dev"
    endif

• 配置board\SConscript

if GetDepend(['BSP_USING_RIL_VDEVICE']):
    src += Glob('ril_vdevice/*.c')

• 添加的文件
  

• 开启AT组件

• 开启配置的ril_dev设备
  

• ril_vdev.c，字符设备的注册，对接xMUX AT收发接口

#include "ril_vdev.h"
#include "board.h"

#ifndef BSP_RIL_VDEVICE_NAME
#define BSP_RIL_VDEVICE_NAME        "ril_dev"
#endif

static struct rt_device _ril_vdev;

static rt_err_t  _ril_vdev_init(rt_device_t dev)
{
    return RT_EOK;
}

static rt_err_t  _ril_vdev_open(rt_device_t dev, rt_uint16_t oflag)
{
    if (dev == RT_NULL)
        return -RT_ERROR;

    return RT_EOK;
}

static rt_err_t _ril_vdev_close(rt_device_t dev)
{
    if (dev == RT_NULL)
        return -RT_ERROR;

    return RT_EOK;
}

rt_size_t _ril_vdev_read(rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
{
    rt_kprintf("%s : buffer = %s, size = %d\r\n", __func__, buffer, size);
    // XMUX_read(buffer, size);
    return RT_EOK;
}

rt_size_t _ril_vdev_write(rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
{
    rt_kprintf("%s : buffer = %s, size = %d\r\n", __func__, buffer, size);
    // XMUX_write(buffer, size);
    return RT_EOK;
}

rt_err_t _ril_vdev_rx_indicate(rt_device_t dev, rt_size_t size)
{
    rt_kprintf("%s : rx_in size = %d\r\n", __func__, size);
    // XMUX_rx_indicate(size);
    return RT_EOK;
}

rt_err_t _ril_vdev_tx_complete(rt_device_t dev, void *buffer)
{
    rt_kprintf("%s : buffer=%s\r\n", __func__, buffer);
    // XMUX_tx_indicate(size);
    return RT_EOK;
}

static rt_err_t _ril_vdev_control(rt_device_t dev, int cmd, void *args)
{
    if (dev == RT_NULL)
        return -RT_ERROR;

    switch (cmd)
    {
        case RIL_VDEV_CTRL_CMD_POWER_ON:
            break;
        case RIL_VDEV_CTRL_CMD_POWER_OFF:
            break;
        default:
            break;
    }

    return RT_EOK;
}

#ifdef RT_USING_DEVICE_OPS
const static struct rt_device_ops ril_vdev_ops =
{
    _ril_vdev_init,
    _ril_vdev_open,
    _ril_vdev_close,
    _ril_vdev_read,
    _ril_vdev_write,
    _ril_vdev_control
};
#endif

static int ril_vdevice_register(const char *name, void *user_data)
{
    _ril_vdev.type         = RT_Device_Class_Char;
    _ril_vdev.rx_indicate  = _ril_vdev_rx_indicate;
    _ril_vdev.tx_complete  = _ril_vdev_tx_complete;

#ifdef RT_USING_DEVICE_OPS
    _ril_vdev.ops          = &ril_vdev_ops;
#else
    _ril_vdev.init         = _ril_vdev_init;
    _ril_vdev.open         = _ril_vdev_open;
    _ril_vdev.close        = _ril_vdev_close;
    _ril_vdev.read         = _ril_vdev_read;
    _ril_vdev.write        = _ril_vdev_write;
    _ril_vdev.control      = _ril_vdev_control;
#endif

    _ril_vdev.user_data    = user_data;

    /* register a character device */
    rt_device_register(&_ril_vdev, name, RT_DEVICE_FLAG_RDWR);

    return 0;
}

int ril_vdevice_init(void)
{
    return ril_vdevice_register(BSP_RIL_VDEVICE_NAME, RT_NULL);
}

• ril_vdev.h 头文件

#ifndef __RIL_VDEV_H__
#define __RIL_VDEV_H__

#include <rtthread.h>
#include <rtdevice.h>

#define RIL_VDEV_CTRL_CMD_POWER_OFF          0xAA00
#define RIL_VDEV_CTRL_CMD_POWER_ON           0xAA01

int ril_vdevice_init(void);

#endif

• ril_app.c，ril device的操作接口，AT client设备的初始化与简单操作

#include "ril_app.h"
#include "at.h"

#define DBG_ENABLE
#define DBG_SECTION_NAME    "rild.test"
#define DBG_LEVEL           DBG_LOG
#include <rtdbg.h>

#ifndef BSP_RIL_VDEVICE_NAME
#define BSP_RIL_VDEVICE_NAME        "ril_dev"
#endif

#ifndef BSP_RIL_RECV_MAX_SIZE
#define BSP_RIL_RECV_MAX_SIZE       1600
#endif

static rt_device_t _ril_dev = RT_NULL;

static rt_device_t get_ril_dev(void)
{
    if (_ril_dev != RT_NULL)
        return _ril_dev;

    _ril_dev = rt_device_find(BSP_RIL_VDEVICE_NAME);

    return _ril_dev;
}

static rt_err_t ril_dev_open(void)
{
    rt_device_t dev = get_ril_dev();
    if (dev == RT_NULL)
        return -RT_ERROR;

    return rt_device_open(dev, RT_DEVICE_FLAG_RDWR);
}

rt_err_t ril_dev_power_on(void)
{
    rt_device_t dev = get_ril_dev();

    if (dev == RT_NULL)
        return -RT_ERROR;

    return rt_device_control(dev, RIL_VDEV_CTRL_CMD_POWER_ON, RT_NULL);
}

rt_err_t ril_dev_power_off(void)
{
    rt_device_t dev = get_ril_dev();

    if (dev == RT_NULL)
        return -RT_ERROR;

    return rt_device_control(dev, RIL_VDEV_CTRL_CMD_POWER_OFF, RT_NULL);
}

rt_err_t ril_dev_init(void)
{
    ril_vdevice_init();
    return ril_dev_open();
}

int ril_at_device_init(void)
{
    ril_dev_init();
    at_client_init(BSP_RIL_VDEVICE_NAME, BSP_RIL_RECV_MAX_SIZE);

    return 0;
}

static void at_response_dump(at_response_t resp)
{
    rt_uint8_t line_num = 0;

    LOG_D("%s: line_counts=%d\n", __func__, resp->line_counts);

    for (line_num = 1; line_num <= resp->line_counts; line_num++)
    {
        const char *resp_line_buf = at_resp_get_line(resp, line_num);

        if (resp_line_buf != RT_NULL)
        {
            LOG_D("%s:line=%d, buf=%s\n", __func__, line_num, resp_line_buf);
        }
    }
}

rt_err_t ril_test_check_sim(void)
{
    at_response_t resp = RT_NULL;

    resp = at_create_resp(64, 3, rt_tick_from_millisecond(500));
    if (resp == RT_NULL)
    {
        LOG_E("%s:at_create_resp error!", __func__);
        return -RT_ERROR;
    }

    at_exec_cmd(resp, "AT+CPIN?");
    at_response_dump(resp);

    if (at_resp_get_line_by_kw(resp, "READY"))
    {
        LOG_D("at_check_sim success.");
        if (resp != RT_NULL)
            at_delete_resp(resp);
        return RT_EOK;
    }

    if (resp != RT_NULL)
        at_delete_resp(resp);
    LOG_E("at_check_sim failed.");
    return -RT_ERROR;
}
MSH_CMD_EXPORT(ril_test_check_sim, ril_test_check_sim);

/* ril_test_at_cmd */
static void ril_test_at_cmd(int argc, char **argv)
{
    at_response_t resp = RT_NULL;

    char *at_cmd = RT_NULL;

    if (argc >= 2)
    {
        at_cmd = argv[1];
    }

    resp = at_create_resp(1024, 4, rt_tick_from_millisecond(1000));
    if (resp == RT_NULL)
    {
        LOG_E("%s:at_create_resp error!", __func__);
        return;
    }

    at_exec_cmd(resp, at_cmd);
    at_response_dump(resp);

    if (resp != RT_NULL)
        at_delete_resp(resp);
}
MSH_CMD_EXPORT(ril_test_at_cmd, ril_test_at_cmd);

INIT_DEVICE_EXPORT(ril_at_device_init);

• ril_app.h 头文件

#ifndef __RIL_APP_H__
#define __RIL_APP_H__

#include "ril_vdev.h"

rt_err_t ril_app_init(void);
rt_err_t ril_vdev_power_on(void);
rt_err_t ril_vdev_power_off(void);
int ril_at_device_init(void);

#endif

测试验证

• 构建、编译、下载，打开串口终端，list_device 查看设备是否正常注册

 \ | /
- RT -     Thread Operating System
 / | \     4.1.0 build Jan 23 2022 13:17:49
 2006 - 2021 Copyright by rt-thread team
_ril_vdev_read : buffer = , size = 1
[I/at.clnt] AT client(V1.3.1) on device ril_dev initialize success.
[I/sensor] rt_sensor[humi_humidity] init success
[I/sensor] rt_sensor[temp_temperature] init success
[I/sensor] rt_sensor[baro_barometer] init success
[I/sensor] rt_sensor[gyro_gyroscope] init success
[I/sensor] rt_sensor[acce_accelerometer] init success
msh >
msh >
msh >
msh >
msh >list_de
list_device
msh >list_device
device           type         ref count
-------- -------------------- ----------
acce_acc Sensor Device        0       
gyro_gyr Sensor Device        0       
baro_bar Sensor Device        0       
temp_tem Sensor Device        0       
humi_hum Sensor Device        0       
ril_dev  Character Device     2    /* 注册的ril AT 字符设备 */   
uart2    Character Device     0       
uart1    Character Device     2       
pin      Miscellaneous Device 0       
msh >

• 测试AT组件，这里使用自己封装的AT组件的命令

msh >ril_test_check_sim
_ril_vdev_write : buffer = AT+CPIN?
, size = 10
[W/at.clnt] execute command (AT+CPIN?) timeout (500 ticks)!
[D/rild.test] at_response_dump: line_counts=0

[E/rild.test] at_check_sim failed.

msh >ril_test_at_cmd AT+CSQ?
_ril_vdev_write : buffer = AT+CSQ?

, size = 9
[W/at.clnt] execute command (AT+CSQ?) timeout (1000 ticks)!
[D/rild.test] at_response_dump: line_counts=0

msh >

• 上面是发送命令，发现已经成功调用了我们注册的ril_dev write接口：_ril_vdev_write，无响应是因为没有使用xMUX接口。xMUX接口需要根据具体Modem xMUX的接口对接。

使用总结

• AT组件对接的是字符设备，不需要一定是uart设备
• 对接xMUX虚拟出来的AT命令接口，需要实现rt_device的

rt_size_t _ril_vdev_read(rt_device_t dev, rt_off_t pos, void *buffer, rt_size_t size)
{
    rt_kprintf("%s : buffer = %s, size = %d\r\n", __func__, buffer, size);
    // XMUX_read(buffer, size);
    return RT_EOK;
}

rt_size_t _ril_vdev_write(rt_device_t dev, rt_off_t pos, const void *buffer, rt_size_t size)
{
    rt_kprintf("%s : buffer = %s, size = %d\r\n", __func__, buffer, size);
    // XMUX_write(buffer, size);
    return RT_EOK;
}

rt_err_t _ril_vdev_rx_indicate(rt_device_t dev, rt_size_t size)
{
    rt_kprintf("%s : rx_in size = %d\r\n", __func__, size);
    // XMUX_rx_indicate(size);
    return RT_EOK;
}

• 后续可以根据AT命令做一个【虚拟Modem】设备，从而让AT组件【空跑】运转起来

小结

• 熟悉AT组件的AT client的使用
• 熟悉AT组件对接Modem RIL层的xMUX AT命令接口的方法