原创 原代码实例：驱动器 in ZRTOS (1)

1、问题综述

在一款车载记录仪中，车载仪需要将以下数据输出：a）记录仪的时钟；b）车辆的VIN号、车牌号码、车牌分类；c）车辆最近360小时内的速度数据；d）最近的10次的停车前20秒内的速度、刹车数据等。输出设备包括：1）U盘；2）打印机；3）手提设备（电脑串口）。如果采用传统的嵌入式系统，要对不同的设备分别编程、调试，然后再把它们integrate在一起，这样不但编程、调试工作量大，而且不利于软件的维护和重复使用。
使用ZRTOS的驱动器理念，只须对上述的a)-d)的功能/features进行编程，使用写/write()而无需考虑是什么设备。这样就大大地减少了编程、调试的工作量，同时也大大地有利于软件的维护和重复使用。
以下是原代码：

A）功能/Features
//get 车辆的VIN号、车牌号码、车牌分类；
void get_VIN_plate(RTOS_FD_TYPE gb_fd) //RTOS_FD_TYPE - file descriptor
{
  char data[44];
  U8 sum;
 
  _mycpy((U8*)data, (U8*)&vehicle_driver.v_info,41);//复制车辆的VIN号、
                                                    //车牌号码、车牌分类；
  sign_header[2]=GET_VIN_PLATE;//国标GB/T19056数据格式
  sign_header[3]=0;//国标GB/T19056数据格式
  sign_header[4]=41;//国标GB/T19056数据格式
  write(gb_fd,sign_header,6);//输出到驱动器
  sum = checksumByte((U8*)sign_header,6);//国标GB/T19056数据格式
  sum += checksumByte((U8*)data,41);//check sum
  data[41] = sum;//国标GB/T19056数据格式
  write(gb_fd,data,42);//输出到驱动器
}
...
//other features here
...

B) USB驱动器和interface
void usb_host_init(void) //USB initialization
{ 
  usbData.sem = rtos_semBCreate(0, SEM_EMPTY);
  rtos_taskSpawn(RTOS_DEFAULT_PRIORITY-2, (RTOS_FUNCPTR) usb_host_tsk,
        (long) 0 ); //spawn a task to handle USB interface
  file_dev.fp = rtos_iosDrvInstall((RTOS_FUNCPTR) NULL, (RTOS_FUNCPTR)
        usb_file_write);//install read() and write() into device driver,
                        //here, read() is NULL or unused
                        //      write() is subroutine usb_file_write()
  rtos_iosDrvAdd((RTOS_FD_TYPE) &file_dev, FILE_IO_0_DEV, file_dev.fp);//add
                //the device driver into device-driver-table
  //...
  //other initialization here
  //... 
}

static RTOS_FD_TYPE usb_file_write(RTOS_FD_TYPE devs, char * buf, size_t num)
{ //write data into USB disk
  int n;
  FILE_DEV * dev = (FILE_DEV *) devs;
  U32 sect;
 
  for(n = 0; n < num; n++) {
    dev->buffer[dev->size++] = buf[n];//move the data into a buffer
    if (dev->size == _SIZE_2_WRITE) { //buffer is full, move data into USB disk's
                                      //sector
      dev->size = 0;
      sect = (file_dev.fat.cluster[file_dev.fat.cluster_num]-2
             *usbData.BPB_SecPerClus + file_dev.fat.sector + usbData.sectRoot;
      //caculate USB disk's sector number
      if (mWriteSector(sect,_NUMBER_SECTORS,dev->buffer)) //do sector write
        return 0; //failed
      file_dev.fat.sector += _NUMBER_SECTORS; //for new FAT in FAT32
      if (file_dev.fat.sector == usbData.BPB_SecPerClus) {//for new FAT
        file_dev.fat.sector = 0; //for new FAT
        file_dev.fat.cluster_num++;//for new FAT
      }
    }
  }
 
  file_dev.fdts.size += num; //for FDT in FAT32
  return num; //return with successful num bytes writing
}

void usb_host_start(void)//this function is called as a USB disk is inserted
{
  CH375_POWER_ON(1); //power on
  usbData.command = 0; //zero command step; the command step is used to return
                       //the correct process step as the USB
                       //interface handler (task) may have to give up the CPU, the user
                       //may find more info later in the "usb_host_tsk()"
  usbData.fd_usb = open(USB_SER_DRV); //open device driver's file descriptor
  rtos_semGive(usbData.sem); //wake up the USB interface handle task
}

static void usb_host_tsk(void) //the USB interface handle task
{
  rtos_semTake(usbData.sem, WAIT_FOREVER);//may pended here
  rtos_semGive(usbData.sem);//give the semaphone to itself so that the task
                            //will continue
  usbData.command++; //incremental the command step
  if(usbData.command==1) { //the command step is equal to 1
    CH375_RST(0);//USB chip hardware reset
    rtos_taskDelay(10);//delay 10 tick or 100ms, the task will give up the CPU
  } else if(usbData.command==2) {
    CH375_WR_CMD_PORT(CMD_RESET_ALL);//USB chip software reset
    rtos_taskDelay(10);
  } else if (usbData.command == 3) {
 
    if (mCH375Init( ))  { //initialize the USB chip
      usb_out();//failed, get out
    }   
    rtos_taskDelay(2);
  } else if (usbData.command == 4) {
    if (mInitDisk()) { //initialize the USB disk
      usb_out();
    }
    rtos_taskDelay(5);
  } else if (usbData.command == 5) {
    displayShortMsg((char *) insert_usb); //show "please wait..." on
                                          //LCD screen
    rtos_taskDelay(250);//200);
  } else if (usbData.command == 6) {
    //...
    //find DBR and MBR of the USB disck
    //...
  } else if (usbData.command == 7) {
    get_VIN_plate(file_dev.fp);//get 车辆的VIN号、车牌号码、车牌分类
    get_vehicle_character(file_dev.fp);//get 车辆特征
    get_real_time_clock(file_dev.fp);//get 记录仪的时钟
    cmd_counter = 0;//a command counter used by get_last360hour_speed() and
                    //get_suspect_acct_data()
                    //in case the task is delay() or pended
  } else if (usbData.command == 8) {
    usbData.command--;
    get_last360hour_speed(file_dev.fp,&cmd_counter);//get 车辆最近360小时内的速度数据
                         //the task may give up the CPU
    cmd_counter = 0;//a command counter used by get_last360hour_speed() and
                    //get_suspect_acct_data()
                    //in case the task is delay() or pended
    usbData.command++;
  } else if (usbData.command == 9) {
    usbData.command--;
    get_suspect_acct_data(file_dev.fp,&cmd_counter);// get 最近的10次的停车前
        //20秒内的速度、刹车数据等 the task may give up the CPU
   usbData.command++;
  } else if (usbData.command == 10) {
    if (!getFat32()) { //finalize the FAT32, FAT, FDT etc.
      usb_return(FALSE);//failed;
    } else
      usb_return(TRUE);//successful
  }
}

C) 串口interface
//国标GB/T 19056 interface initialization code here
GB_data.timeout = WAIT_FOREVER;//never time out or task read_GB_tsk() shall
                               //pended util other release the semaphone
...
//other initialization here
//
当车载仪收到国标GB/T 19056的指令时，
GB_data.command = 国标GB/T 19056的指令；
GB_data.timeout = 4；//wait for 4 tick or 40 ms
GB_data.fp = open(SCI_IO_DEV1);//open 国标GB/T 19056 or 串口 device driver's file                   
                               //descriptor
rtos_semGive(GB_data.sem); //wake up read_GB_tsk()
...
（略）
...
//

//
static void read_GB_tsk(void)//task to handle GB/T 19056 commands
{
  long result = rtos_semTake(GB_data.sem, GB_data.timeout);
  if (result == (long) OK) return;//it is not timeout
 
  switch (GB_data.command) {
    case GET_DRIVER_ID_LICENSE:
    get_driver_id_lisence(GB_data.fp);
    break;
    case GET_REAL_TIME_CLOCK:
    get_real_time_clock(GB_data.fp);
    break;
    case GET_LAST360HOUR_MILES:
    get_last360hour_miles(GB_data.fp，&GB_data.cnt);
    break;
    case GET_VEHICLE_CHARACTER:
    get_vehicle_character(GB_data.fp);
    break;
    case GET_LAST360HOUR_SPEED:
    get_last360hour_speed(GB_data.fp，&GB_data.cnt);
    break;
    case GET_VIN_PLATE:
    get_VIN_plate(GB_data.fp);
    break;
    case GET_SUSPECT_ACCNT_DATA:
    get_suspect_acct_data(GB_data.fp，&GB_data.cnt);
    break;
    //
    //（略）
    //
    default:
    break;
  }
 
  //no problem, out here
  GB_data.timeout = WAIT_FOREVER;
  GB_data.cmd = GB_data.current = 0;
}

2、结论
使用驱动器理念，可以清晰地定义功能和设备以及它们之间的联系，可以大大地减少了编程、调试的工作量，比如在本例中，串口的驱动器 is well defined, thus the programmers call easily start from GB/T 19056 protocol and get those features (such as get_last360hour_speed(), etc.) done/搞定 first. The group who process USB interface shall focus on their attention to the USB hardware interface (they may also get a short cut by using other project's device driver codes). 同时使用驱动器理念也大大地有利于软件的维护和重复使用。
另外，ZRTOS中的驱动器的使用方式和效果与vxWorks基本相同。