pixhawk启动脚本分析

Nuttx系统启动是由ardupilot/mk/PX4/ROMFS/init.d里的rcS和rc.APM完成的。笔者阅读了rcS和rc.APM，该脚本类似C语言，并做了相关注释。主要是一些设备自检，启动各模块，最后启动进入ArduPilot_main，开始运行程序。本节只介绍启动脚本，程序的启动与整体运行下节再分析。

rcS

rcS
#!nsh由nsh进行解析的脚本
#
# PX4FMU startup script.
#
# This script is responsible for:这个脚本是为了回应
#
# - mounting the microSD card (if present)安装SD卡
# - running the user startup script from the microSDcard (if present)从SD卡中运行用户启动脚本
# - detecting the configuration of the systemand picking a suitable查找系统配置并选择一个合适的启动脚
#  startup script to continue with                                      本继续运行
#
# Note: DO NOT add configuration-specificcommands to this script;
#      add them to the per-configuration scripts instead.
#
 
#
# Default to auto-start mode.  An initscript on the microSD card
# can change this to prevent automatic startupof the flight script.
#
set MODE autostart  模式设置为自动开始   MODE跟USB应该是环境变量
set USB autoconnect  USB自动连接        在Linux中也是用set去给一个环境变量赋值的
 
#
 
#
 
 
if rgbled start  亮灯的设置，有就亮白灯
then
       set HAVE_RGBLED 1
        #show startup white 
        rgbled rgb 16 16 16
else
       set HAVE_RGBLED 0
fi
 
#
# Try to mount the microSD card.尝试挂载SD卡
#
echo "[init]looking for microSD..."echo是打印的命令
if mount -t vfat/dev/mmcsd0 /fs/microsdmount [-t vfstype] [-ooptions] device dir.
then                                   -t vfstype指定文件系统的类型，通常不必指定，fat32文件系统：vfat
    echo"[init] card mounted at /fs/microsd"      /dev/mmcsd0指SD卡  /fs/microsd指挂载目录
       set HAVE_MICROSD 1
    # Startplaying the startup tune    产生启动语调，表示启动成功
    tone_alarm1
else
       set HAVE_MICROSD 0
    echo"Trying format of microSD"
       tone_alarm MBAGP
        ifmkfatfs /dev/mmcsd0     格式化SD卡
       then
        echo "microSD card formatted"
               if mount -t vfat /dev/mmcsd0 /fs/microsd    挂载SD卡
               then
                        echo "formatsucceeded"
                        set HAVE_MICROSD 1
                        tone_alarm 1
               else
                        echo "mountfailed"
                        tone_alarm MNBG          挂载失败的语调
                        if [ $HAVE_RGBLED == 1]
                        then
                           rgbled rgb 16 0 0     挂载失败的灯
                        fi
               fi
       else                      格式化失败
             echo"format failed"
               tone_alarm MNBGG    挂载失败的语调
               if [ $HAVE_RGBLED == 1 ]
               then
                        rgbled rgb 16 0 0  挂载失败的灯
               fi
            fi
fi
 
#
# Look for an initscript on the microSD card.    寻找初始化脚本
#
# To prevent automatic startup in the currentflight mode,为了避免自动启动当前飞行模式，脚本应该设置成
# the script should set MODE to some othervalue.          其他值
#
if [ -f /fs/microsd/etc/rc ]      查找/fs/microsd/etc/rc这个路径的rc文件
then
    echo"[init] reading /fs/microsd/etc/rc"
    sh /fs/microsd/etc/rc         执行rc文件   sh是用来执行nsh脚本的一个命令
fi
# Also consider rc.txt files
if [ -f /fs/microsd/etc/rc.txt ]查找/fs/microsd/etc/rc.txt这个路径的rc文件
then
    echo"[init] reading /fs/microsd/etc/rc.txt"
    sh /fs/microsd/etc/rc.txt 执行rc.txt文件
fi
 
#
# Check for USB host
#
if [ $USB != autoconnect]    判断USB不是自动连接
then
    echo"[init] not connecting USB"
else
    if sercon     初始化USB串口
    then
        echo"[init] USB interface connected"
    else
        echo"[init] No USB connected"
    fi
fi
 
if [ $HAVE_MICROSD == 0 ]    判断是否有SD卡
then
        ifusb_connected
       then
               echo "Opening USB nsh"
       else
               echo "booting with no microSD"
               set HAVE_MICROSD 1
        fi
fi
 
# if this is an APM build then there will be arc.APM script如果这是APM build，那么会有rc.APM脚本文件
# from an EXTERNAL_SCRIPTS build option        rc.APM脚本文件来自EXTERNAL_SCRIPTS(外部脚本)build选项中
if [ -f /etc/init.d/rc.APM -a $HAVE_MICROSD == 1-a ! -f /fs/microsd/APM/nostart ]
then
    echoRunning rc.APM
    # ifAPM startup is successful then nsh will exit
    sh /etc/init.d/rc.APM          执行/etc/init.d/rc.APM文件
else
        nshterm /dev/ttyACM0&
fi

其实我们完全把它当作一个 Linux脚本来阅读就可以了。
    MODE跟 USB应该是环境变量，在Linux中也是用 set去给一个环境变量赋值的。然后去启动 “rgbled”，这是由 “Firmware”提供的。我们很容易猜到这是用来控制那个高亮的 LED灯的。然后才是挂载 SD卡，文件系统为 vfat，挂载目录为 /fs/microsd。 SD卡挂载上来之后就去执行 SD卡中的脚本 “/fs/microsd/etc/rc”，所以我们就知道 sh是用来执行 nsh脚本的一个命令。应该来说 “/fs/microsd/etc/rc.txt”也是一个脚本，要不然也不会使用 sh命令了。 sercon你需要去看下源码才知道这是用来初始化 USB串口的。而最后则是通过调用 /etc/init.d/rc.APM脚本来真正初始化飞控。

rc.APM

#!nsh  由nsh进行解析的脚本
 
# APM startup script for NuttX on PX4    APM的Nuttx系统启动脚本
 
# To disable APM startup add a /fs/microsd/APM/nostart file
# To enable mkblctrlstartup add a /fs/microsd/APM/mkblctrl file
# To enable mkblctrl_+ startup add a /fs/microsd/APM/mkblctrl_+file
# To enable mkblctrl_x startup add a /fs/microsd/APM/mkblctrl_xfile
# To enable PWM on FMUv1 on ttyS1 add a /fs/microsd/APM/AUXPWM.enfile
 
set deviceA /dev/ttyACM0
 
# check for an old file called APM, caused by 核查一个叫APM旧的文件
# a bug in an earlier firmware release         它由firmware发布，为了应对之前的一个bug
if [ -f /fs/microsd/APM ]
then
   echo"APM file found - renaming"
   mv /fs/microsd/APM /fs/microsd/APM.old   将/fs/microsd/APM命名为/fs/microsd/APM.old
fi
 
if [ -f /fs/microsd/APM/nostart]是否找到/fs/microsd/APM/nostart文件
then
   echo"APM/nostart found - skipping APMstartup"
   sh /etc/init.d/rc.error    执行/etc/init.d/rc.error
fi
 
# mount binfsso we can find the built-in apps挂载binfs(built_in_files)文件，这样就可以找到built-in应
if [ -f /bin/reboot ]         查找/bin/reboot文件                                       用程序
then
    echo"binfs already mounted"
else
    echo"Mounting binfs"
        ifmount -t binfs /dev/null/bin   将binfs挂载到/bin目录下
       then
               echo "binfs mounted OK"
       else
               sh /etc/init.d/rc.error    执行/etc/init.d/rc.error
        fi
fi
 
set sketch NONE            设置环境变量sketch为NONE
if rm /fs/microsd/APM/boot.log    删除(remove)/fs/microsd/APM/boot.log
then
   echo"removed old boot.log"
fi
set logfile /fs/microsd/APM/BOOT.LOG  将logfile文件设置成/fs/microsd/APM/BOOT.LOG文件
 
if [ ! -f /bin/ArduPilot ]           查找/bin/ArduPilot文件
then
   echo"/bin/ardupilot not found"
   sh /etc/init.d/rc.error
fi
 
if mkdir /fs/microsd/APM >/dev/null    生成/fs/microsd/APM/dev/null目录(猜测)
then
     echo"Created APM directory"
fi

这部分是我划出来的第一部分。先设置串口，然后一堆跟SD卡相关的命令。其实我们将一张空的SD卡放进去也是可以正常工作的。可能这里最让人感兴趣的就是“ArduPilot”了，因为APM工程就叫“ArduPilot”。在 g_builtins数组中也有这样一行信息：

{"ArduPilot",SCHED_PRIORITY_DEFAULT, 4096, ArduPilot_main},
也就是说 PX4将 APM原来的主程序设计成了 Nuttx中的一个命令。但其实我们在使用 Linux系统的时候，可执行文件其实就等同命令。这个命令跟其他命令还是有很大不同的，这个我们后面再讨论。

if [ -f /bin/px4io ]   查找/bin/px4io文件
then
  if [ -f/bin/lsm303d ]   查找/bin/lsm303d
  then
     echo"Detected FMUv2 board"
     setBOARD FMUv2           将BOARD设置成FMUv2
  else
     echo"Detected FMUv1 board"
     setBOARD FMUv1            将BOARD设置成FMUv1
  fi
else
  echo"Detected FMUv4 board"
  setBOARD FMUv4              将BOARD设置成FMUv4
fi
 
if [ $BOARD == FMUv1 ]      从这开始是对deviceC和D的设置
then
   setdeviceC /dev/ttyS2
   if [ -f/fs/microsd/APM/AUXPWM.en]
   then           To enablePWM on FMUv1 on ttyS1 add a /fs/microsd/APM/AUXPWM.en file
      setdeviceD /dev/null
   else
      setdeviceD /dev/ttyS1
   fi
else
   setdeviceC /dev/ttyS1
   setdeviceD /dev/ttyS2
fi
 
if uorb start         uorb是否被设置为start
then
    echo"uorb started OK"
else
    sh /etc/init.d/rc.error
fi

从这里我们可以看到FMUv1跟 FMUv2的差别在于 lsm303d这颗传感器。通过这颗传感器我们可以用肉眼进行区分。当然它们所使用的串口不同这个可能就无法直接看到了。

我看了下 uorb的源码，源码中有这样一条注释：“Start/load the driver”，我没太搞懂这里 “driver”是什么，只是它用到了一个变量：PX4IO *g_dev = nullptr;，由此也只能确定这是跟 IO板相关的，更具体的就不知道了。

 

# start mkblctrldriver if configured   启动mkblctrl驱动，如果mkblctrl被配置了
if [ -f /fs/microsd/APM/mkblctrl]
then
    echo"Setting up mkblctrl driver"
    echo"Setting up mkblctrl driver">> $logfile          写入logfile
    mkblctrl -d /dev/pwm_output
fi
 
if [ -f /fs/microsd/APM/mkblctrl_+ ]
then                     Toenable mkblctrl_+ startup add a /fs/microsd/APM/mkblctrl_+ file
    echo"Setting up mkblctrl driver +"
    echo"Setting up mkblctrl driver +">> $logfile
    mkblctrl -mkmode +-d /dev/pwm_output
fi
 
if [ -f /fs/microsd/APM/mkblctrl_x ]
then                      Toenable mkblctrl_x startup add a /fs/microsd/APM/mkblctrl_x file
    echo"Setting up mkblctrl driver x"
    echo"Setting up mkblctrl driver x">> $logfile
    mkblctrl -mkmode x-d /dev/pwm_output
fi
这一段我想应该是比较好理解的，就算我们不去看这个命令，因为这里是在设置机型。
 
if [ -f /bin/px4io ]
then
  echo"Trying PX4IO board"
 
  # trythe px4io start twice. Some FMUv2 board don't再次启动px4io，因为有些FMUv2板第一次启动会不成功
  # comeup the first time
  setHAVE_PX4IO false
  if px4iostart norc     px4是否启动正常
  then
    setHAVE_PX4IO true    将HAVE_PX4IO设置为true
  else
    # itmay be in bootloader mode      此时应该在bootloader模式
    echoLoading /etc/px4io/px4io.bin   下载/etc/px4io/px4io.bin文件到板中
   tone_alarm MBABGP                    发出MBABGP的提示语调
    ifpx4io update /etc/px4io/px4io.bin   判断px4是否跟新成/etc/px4io/px4io.bin
    then
    echo"upgraded PX4IO firmware OK"
       tone_alarm MSPAA                  发出MSPAA的提示语调
    else
    echo"Failed to upgrade PX4IO firmware"
       tone_alarm MNGGG                  发出MNGGG的提示语调
    fi
    sleep1
    ifpx4io start norc  px4是否启动正常
    then
       set HAVE_PX4IO true   将HAVE_PX4IO设置为true
        #play happy tune again
    tone_alarm1             发出1号提示语调
    fi
  fi
else          找不到/bin/px4io
    setHAVE_PX4IO false
    echo"No PX4IO support"
fi
 
if [ $HAVE_PX4IO == true ]
then
    echo"PX4IO board OK"
    ifpx4io checkcrc /etc/px4io/px4io.bin   校验/etc/px4io/px4io.bin通过CRC校验判断是否需要更新的
    then
       echo "PX4IO CRC OK"
    else
       echo "PX4IO CRC failure"
       echo "PX4IO CRC failure" >> $logfile   
       tone_alarm MBABGP            发出MBABGP的提示语调
 
        ifpx4io safety_on      
       then
           echo "PX4IO disarm OK"
       else
           echo "PX4IO disarm failed"
        fi
 
       sleep 1
 
        ifpx4io forceupdate 14662 /etc/px4io/px4io.bin        强制跟新/etc/px4io/px4io.bin
       then
              sleep 1
              if px4io start norc       px4是否启动正常
              then
                 echo "PX4IO restart OK"
                 echo "PX4IO restart OK" >> $logfile    写入logfile
                 tone_alarm MSPAA
              else
                 echo "PX4IO restart failed"
                 echo "PX4IO restart failed" >> $logfile   
                 tone_alarm MNGGG
                 sh /etc/init.d/rc.error          执行/etc/init.d/rc.error
              fi
       else
              echo "PX4IO update failed"
              echo "PX4IO update failed" >> $logfile   
              tone_alarm MNGGG
        fi
    fi
else     HAVE_PX4IO=false
    echo"No PX4IO board found"
    echo "No PX4IO board found">> $logfile
 
    if [$BOARD == FMUv2 ] FMUv4不需要PX4IO，通过/bin/lsm303d传感器文件，判断是FMUv2还是FMUv1
    then
       sh/etc/init.d/rc.error
    fi
fi

这里看似很长的一段脚本，其实质做了一件事情：更新IO板的固件。这么长的脚本处理了两种情况：一、IO板没有固件；二，IO板有固件但不是最新的。更新固件是通过 px4io命令来完成的，如果我们想知道固件是如何更新的可以去阅读该命令的源码。固件更新其实我们在分析 IO板的启动的时候已经知道是通过 CRC校验判断是否需要更新的。

 

if [ $BOARD == FMUv1 -a $deviceD == /dev/ttyS1 ]   判断板子是否是FMUV1，deviceD是否对应/dev/ttyS1
then
       echo "Setting FMU mode_serial"
       fmu mode_serial     将fmu设置为串口模式
else
        iffmu mode_pwm4    将fmu设置为pwm模式
       then
               echo "Set FMU mode_pwm4"
        fi
fi

我粗略看了下 fmu的源码，没看明白这一段是干嘛的。

 

if mtd start /fs/mtd MTD(memory technology device内存技术设备)用于访问memory设备（ROM，Flash）的子系统
then   linux中MTD的主要目的是为了使新的memory设备的驱动更加简单，为此它在硬件和上层之间提供了一个
    echo"started mtd driver OK"            抽象的接口,MTD的所有源代码在/driver/mtd子目录中
else
    echo"failed to start mtd driver"
    echo"failed to start mtd driver" >> $logfile
    sh/etc/init.d/rc.error          
fi
 
if mtd readtest /fs/mtd
then
    echo"mtd readtest OK"           读mtd测试
else
    echo"failed to read mtd"
    echo"failed to read mtd" >> $logfile
    sh/etc/init.d/rc.error          
fi
 
if [ $BOARD == FMUv2 -o $BOARD == FMUv4 ]
then
  # theramtron on FMUv2 is very fast and can handle trillions of 之前有个设备读写失败了，所以进行读
  #writes. This full rw test on each boot ensures it is working    写测试，确保读写没问题
  #properly. We have one board that failed this, so
  # thetest is arguably worth having
  if mtdrwtest /fs/mtd    mtd读写测试
  then
    echo"mtd rwtest OK"
  else
    echo"failed to test mtd"
    echo"failed to test mtd" >> $logfile
    sh/etc/init.d/rc.error          
  fi
fi

对mtd进行读写测试，确保这方面没问题。这部分脚本是对mtd的操作，根据对Linux的了解，我觉得这里应该跟存储设备相关。虽然没有mount操作，但我仍然觉得这里可能是挂载存储设备，具体的仍然要到源码中去找寻答案。

 

echo "Starting APM sensors"
 
if ms5611 start启动ms5611
then
   echo"ms5611 started OK"
else
   echo"no ms5611 found"
   echo"No ms5611 found" >> $logfile
   sh/etc/init.d/rc.error
fi
 
if adc start 启动adc
then
   echo"adc started OK"
else
   echo"No adc" >> $logfile
   sh/etc/init.d/rc.error
fi
 
if [ $BOARD == FMUv1 ]         板子为FMUv1
then
    echo"Starting FMUv1 sensors"
    ifhmc5883 -C -T -X start         启动hmc5883
    then
       echo "Have external hmc5883"
    else
       echo "No external hmc5883"
    fi
    ifhmc5883 -C -T -I  start
    then
       echo "Have internal hmc5883"
    else
       echo "No internal hmc5883"
    fi
    ifmpu6000 start           启动mpu6000
    then
      echo "mpu6000  startedOK"
    else
       sh/etc/init.d/rc.error
    fi
    ifl3gd20 start              启动l3gd20
    then
      echo "l3gd20 started OK"
    else
      echo "No l3gd20"
      echo "No l3gd20" >> $logfile
    fi
fi
 
if [ $BOARD == FMUv2 ]      板子为FMUv2
then
    echo"Starting FMUv2 sensors"
    ifhmc5883 -C -T -X start
    then
       echo "Have external hmc5883"
    else
       echo "No external hmc5883"
    fi
    ifhmc5883 -C -T -I -R 4 start
    then
        echo "Have internal hmc5883"
    else
       echo "No internal hmc5883"
    fi
 
    #external MPU6000 is rotated YAW_180 from standard
    ifmpu6000 -X -R 4 start
    then
      echo "Found MPU6000 external"
       setHAVE_FMUV3 true
    else
       ifmpu9250 -X -R 4 start
      then
          echo "Found MPU9250 external"
          set HAVE_FMUV3 true
      else
          echo "No MPU6000 or MPU9250 external"
          set HAVE_FMUV3 false
       fi
    fi
    if [$HAVE_FMUV3 == true ]
    then
        #external L3GD20 is rotated YAW_180 from standard
        ifl3gd20 -X -R 4 start
       then
              echo "l3gd20 external started OK"
       else
              echo "No l3gd20"
              sh /etc/init.d/rc.error
        fi
        #external LSM303D is rotated YAW_270 from standard
        iflsm303d -a 16 -X -R 6 start
       then
              echo "lsm303d external started OK"
       else
              echo "No lsm303d"
              sh /etc/init.d/rc.error
        fi
        #internal MPU6000 is rotated ROLL_180_YAW_270 from standard
        ifmpu6000 -R 14 start
       then
              echo "Found MPU6000 internal"
       else
          if mpu9250 -R 14 start
          then
              echo "Found MPU9250 internal"
          else
              echo "No MPU6000 or MPU9250"
              echo "No MPU6000 or MPU9250" >> $logfile
              sh /etc/init.d/rc.error
          fi
        fi
        ifhmc5883 -C -T -S -R 8 start
       then
              echo "Found SPI hmc5883"
        fi
    else
        ifmpu6000 start
       then
              echo "Found MPU6000"
       else
              if mpu9250 start
              then
                   echo "FoundMPU9250"
              else
                   echo "No MPU6000 orMPU9250"
                   echo "No MPU9250">> $logfile
              fi
        fi
        ifl3gd20 start
       then
              echo "l3gd20 started OK"
       else
              sh /etc/init.d/rc.error
        fi
        iflsm303d -a 16 start
       then
              echo "lsm303d started OK"
       else
              sh /etc/init.d/rc.error
        fi
    fi
fi
 
 
if [ $BOARD == FMUv4 ]         板子为FMUv4
then
    echo"Starting FMUv4 sensors"
    ifhmc5883 -C -T -X start
    then
       echo "Have external hmc5883"
    else
       echo "No external hmc5883"
    fi
    ifhmc5883 -C -T -S -R 2 start
    then
       echo "Have SPI hmc5883"
    else
       echo "No SPI hmc5883"
    fi
 
    ifmpu6000 -R 2 -T 20608 start
    then
      echo "Found ICM-20608 internal"
    fi
 
    ifmpu9250 -R 2 start
    then
      echo "Found mpu9250 internal"
    fi
fi

从 echo那一句很容易看出这里是在启动传感器。当然，我暂时是不会去研究这些传感器是干嘛用的，只以看流程为主。从这段脚本我们也可以看出 V1跟 V2的一些区别，即 V1是内置罗盘，并且上电校准。但是 V2可以使用外置罗盘，而且上电过程是不校准的。至于陀螺为什么会有内部和外部的区别这个我没想通，也没有找到相关资料，这或许就要到源码中去寻找答案了。而源码肯定是要去看的。

 

# optional ETS airspeed sensor  空速计
if ets_airspeed start
then
    echo"Found ETS airspeed sensor"
fi
 
if meas_airspeed start
then
    echo"Found MEAS airspeed sensor"
else
    ifmeas_airspeed start -b 2
    then
       echo "Found MEAS airspeed sensor (bus2)"
    fi
fi
 
# optional Range Finder sensor  测距仪
if ll40ls -X start
then
    echo"Found external ll40ls sensor"
fi
 
if ll40ls -I start
then
    echo"Found internal ll40ls sensor"
fi
 
if trone start
then
    echo"Found trone sensor"
fi
 
if mb12xx start
then
    echo"Found mb12xx sensor"
fi
 
# optional PX4Flow sensor     光流
if [ -f /bin/px4flow ]
then
  ifpx4flow start
  then
    echo"Found px4flow sensor"
  fi
fi
 
# optional PWM input driver     pwm输入驱动
if pwm_input start
then
    echo"started pwm_input driver"
fi
 
# optional oreo leds    oled屏
if [ -f /bin/oreoled ]
then
  iforeoled start autoupdate
  then
    echo "oreoledstarted OK"
  fi
fi
 
# optional smbus battery monitor   电池总线监视器
if batt_smbus -b 2 start
then
    echo"Found batt_smbus"
fi
 
# optional irlock     irlock暂时不知道是什么
if irlock start
then
    echo"irlock started"
fi
 
echo Starting ArduPilot $deviceA $deviceC$deviceD
if ArduPilot -d $deviceA -d2 $deviceC -d3$deviceD start   启动deviceA、deviceC、deviceD
then
    echo ArduPilot started OK
else
    sh/etc/init.d/rc.error
fi
 
echo "rc.APM finished"

最后还有一个人脚本： /etc/init.d/rc.error，在出错的时候我们经常看到这个脚本。

rc.error

echo "Error in startup"
 
tone_alarm MNCC
 
if [ $HAVE_RGBLED == 1 ]
then
        rgbled rgb16 0 0
fi
 
nshterm/dev/ttyACM0 &     启动/dev/ttyACM0
sleep 1
nshterm/dev/ttyS0 &       启动/dev/ttyS0
sleep 1
exit

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