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衡水龙腾网站建设,杭州大的做网站的公司,公司门户网站源码,公司网站管理维护BetaFlight飞控启动运行过程简介 1. 源由2. 启动过程2.1 main#xff08;主程序#xff09;2.2 init #xff08;初始化#xff09;2.3 run 3. 任务调度3.1 任务定义3.2 scheduler (调度器) 4. 总结5. 参考资料6. 附录 – 问题汇总6.1 Why desiredPeriodCycles is so … BetaFlight飞控启动运行过程简介 1. 源由2. 启动过程2.1 main主程序2.2 init 初始化2.3 run 3. 任务调度3.1 任务定义3.2 scheduler (调度器) 4. 总结5. 参考资料6. 附录 – 问题汇总6.1 Why desiredPeriodCycles is so important to Betaflight task?6.2 What root cause has made gyro task to been overrun, so scheduler has to skip a gyro cycle?6.3 What if serial task is running quite long, which corrupt gyro cycle, is it a problem?6.4 What does the condition of scheduleCount SCHED_TASK_DEFER_MASK 0 stand for in scheduler? 1. 源由 BetaFlight经过工程结构、代码框架、传感模块框架、统一硬件配置文件这一路的研读让我们对BetaFlight飞控系统更多的了解。 BetaFlight开源工程结构简明介绍BetaFlight开源代码框架简介BetaFlight深入传感设计传感模块设计框架BetaFlight统一硬件配置文件研读 逐步领悟到结构化设计的优势的同时为了更好的理解整体系统如何融合在一起我们将会进入本章BetaFlight飞控启动和运行过程这也是SOC系统初始化的主轴。

1. 启动过程 作为C语言级别启动过程的入口相信大家都很容易就想到了Linux应用程序之Helloworld入门。 因此我们这里就是从main入口开始分析的详见下面代码走读。 2.1 main主程序 不错C的入口就是main程序而BetaFlight是用C语言开发的一款飞控项目其入口当然亦是如此详见betaflight\src\main\main.c。 整体上分为两部分初始化和运行。 main├── init└── run注飞控基本上电池拔掉就好了没有复杂的去初始化过程。这也体现了航模的专属特性 _ 2.2 init 初始化 整个初始化流程是比较长的所以看这个初始化流程真的比较辛苦但是从流程的角度来说注意以下几点 初始化步骤逐一自上而下执行初始化可能存在硬件初始化和应用初始化应用对应的硬件初始化应早于应用执行初始化应用之前有耦合的需要根据依赖关系初始化 笔者阅读代码时整个函数长度 1000 - 258 742 代码行含空行非常可怕的一个函数。 注如果能够进行归纳整理进行应用功能块区分就好了可惜目前代码尚没有做到这点。 init├── SERIAL_PORT_COUNT printfSerialInit├── systemInit├── tasksInitData├── IOInitGlobal├── USE_HARDWARE_REVISION_DETECTION detectHardwareRevision├── USE_TARGET_CONFIG targetConfiguration├── pgResetAll├── USE_SDCARD_SPI configureSPIBusses(); initFlags | SPI_BUSSES_INIT_ATTEMPTED;├── sdCardAndFSInit; initFlags | SD_INIT_ATTEMPTED;├── !sdcard_isInserted() failureMode(FAILURE_SDCARD_REQUIRED)├── [SD Card FS check] //while (afatfs_getFilesystemState() ! AFATFS_FILESYSTEM_STATE_READY)│ ├── afatfs_poll()│ └── afatfs_getFilesystemState() AFATFS_FILESYSTEM_STATE_FATAL failureMode(FAILURE_SDCARD_INITIALISATION_FAILED)├── CONFIG_IN_EXTERNAL_FLASH || CONFIG_IN_MEMORY_MAPPED_FLASH)│ ├── pgResetAll()│ ├── CONFIG_IN_EXTERNAL_FLASH configureSPIBusses(); initFlags | SPI_BUSSES_INIT_ATTEMPTED;│ ├── configureQuadSPIBusses();configureOctoSPIBusses();initFlags | QUAD_OCTO_SPI_BUSSES_INIT_ATTEMPTED;│ ├── bool haveFlash flashInit(flashConfig());│ ├── !haveFlashfailureMode(FAILURE_EXTERNAL_FLASH_INIT_FAILED)│ └── initFlags | FLASH_INIT_ATTEMPTED├── initEEPROM├── ensureEEPROMStructureIsValid├── bool readSuccess readEEPROM()├── USE_BOARD_INFO initBoardInformation├── !readSuccess || !isEEPROMVersionValid() || strncasecmp(systemConfig()-boardIdentifier, TARGET_BOARD_IDENTIFIER, sizeof(TARGET_BOARD_IDENTIFIER)) resetEEPROM()├── systemState | SYSTEM_STATE_CONFIG_LOADED├── USE_DEBUG_PIN dbgPinInit├── debugMode systemConfig()-debug_mode├── TARGET_PREINIT targetPreInit├── !defined(USE_VIRTUAL_LED) ledInit(statusLedConfig())├── !defined(SIMULATOR_BUILD) EXTIInit├── USE_BUTTONS│ ├── buttonsInit│ └── EEPROM_RESET_PRECONDITION defined(BUTTON_A_PIN) defined(BUTTON_B_PIN) //#define EEPROM_RESET_PRECONDITION (!isMPUSoftReset())│ └── resetEEPROM/systemReset├── defined(STM32F4) || defined(STM32G4) // F4 has non-8MHz boards, G4 for Betaflight allow 24 or 27MHz oscillator│ └── systemClockSetHSEValue(systemConfig()-hseMhz * 1000000U)├── USE_OVERCLOCK OverclockRebootIfNecessary(systemConfig()-cpu_overclock)├── USE_MCO│ ├── defined(STM32F4) || defined(STM32F7)│ │ └── mcoConfigure(MCODEV_2, mcoConfig(MCODEV_2));│ └── defined(STM32G4)│ └── mcoConfigure(MCODEV_1, mcoConfig(MCODEV_1));├── USE_TIMER timerInit├── BUS_SWITCH_PIN busSwitchInit├── defined(USE_UART) !defined(SIMULATOR_BUILD) uartPinConfigure(serialPinConfig())├── [serialInit]│ ├── AVOID_UART1_FOR_PWM_PPM serialInit(featureIsEnabled(FEATURE_SOFTSERIAL), featureIsEnabled(FEATURE_RX_PPM) || featureIsEnabled(FEATURE_RX_PARALLEL_PWM) ? SERIAL_PORT_USART1 : SERIAL_PORT_NONE);│ ├── AVOID_UART2_FOR_PWM_PPM serialInit(featureIsEnabled(FEATURE_SOFTSERIAL), featureIsEnabled(FEATURE_RX_PPM) || featureIsEnabled(FEATURE_RX_PARALLEL_PWM) ? SERIAL_PORT_USART2 : SERIAL_PORT_NONE);│ ├── AVOID_UART3_FOR_PWM_PPM serialInit(featureIsEnabled(FEATURE_SOFTSERIAL), featureIsEnabled(FEATURE_RX_PPM) || featureIsEnabled(FEATURE_RX_PARALLEL_PWM) ? SERIAL_PORT_USART3 : SERIAL_PORT_NONE);│ └── else serialInit(featureIsEnabled(FEATURE_SOFTSERIAL), SERIAL_PORT_NONE)├── mixerInit(mixerConfig()-mixerMode)├── uint16_t idlePulse motorConfig()-mincommand├── featureIsEnabled(FEATURE_3D) idlePulse flight3DConfig()-neutral3d├── motorConfig()-dev.motorPwmProtocol PWM_TYPE_BRUSHED idlePulse 0; // brushed motors├── USE_MOTOR motorDevInit(motorConfig()-dev, idlePulse, getMotorCount()); systemState | SYSTEM_STATE_MOTORS_READY├── USE_RX_PPM featureIsEnabled(FEATURE_RX_PARALLEL_PWM) pwmRxInit(pwmConfig())├── USE_BEEPER beeperInit(beeperDevConfig())├── defined(USE_INVERTER) !defined(SIMULATOR_BUILD) initInverters(serialPinConfig())├── [Hardware Bus Initialization]│ ├── TARGET_BUS_INIT targetBusInit()│ └── else │ ├── !(initFlags SPI_BUSSES_INIT_ATTEMPTED) configureSPIBusses();initFlags | SPI_BUSSES_INIT_ATTEMPTED;│ ├── !(initFlags QUAD_OCTO_SPI_BUSSES_INIT_ATTEMPTED) configureQuadSPIBusses();configureOctoSPIBusses();initFlags | QUAD_OCTO_SPI_BUSSES_INIT_ATTEMPTED;│ ├── defined(USE_SDCARD_SDIO) !defined(CONFIG_IN_SDCARD) defined(STM32H7) sdioPinConfigure(); SDIO_GPIO_Init();│ ├── USE_USB_MSC│ │ ├── mscInit()│ │ └── USE_SDCARD blackboxConfig()-device BLACKBOX_DEVICE_SDCARD sdcardConfig()-mode !(initFlags SD_INIT_ATTEMPTED) sdCardAndFSInit();initFlags | SD_INIT_ATTEMPTED;│ ├── USE_FLASHFS blackboxConfig()-device BLACKBOX_DEVICE_FLASH emfat_init_files│ ├── USE_SPI spiInitBusDMA│ ├── mscStart() 0 mscWaitForButton();│ ├── mscStart() ! 0 systemResetFromMsc()│ ├── USE_PERSISTENT_MSC_RTC│ │ ├── persistentObjectWrite(PERSISTENT_OBJECT_RTC_HIGH, 0);│ │ └── persistentObjectWrite(PERSISTENT_OBJECT_RTC_LOW, 0);│ └── USE_I2C│ ├── i2cHardwareConfigure(i2cConfig(0));│ ├── USE_I2C_DEVICE_1 i2cInit(I2CDEV_1);│ ├── USE_I2C_DEVICE_2 i2cInit(I2CDEV_2);│ ├── USE_I2C_DEVICE_3 i2cInit(I2CDEV_3);│ └── USE_I2C_DEVICE_4 i2cInit(I2CDEV_4);├── USE_HARDWARE_REVISION_DETECTION updateHardwareRevision ├── USE_VTX_RTC6705 bool useRTC6705 rtc6705IOInit(vtxIOConfig());├── USE_CAMERA_CONTROL cameraControlInit();├── USE_ADC adcInit(adcConfig());├── initBoardAlignment(boardAlignment());├── !sensorsAutodetect()│ ├── isSystemConfigured()│ │ └── indicateFailure(FAILURE_MISSING_ACC, 2);│ └── setArmingDisabled(ARMING_DISABLED_NO_GYRO);├── systemState | SYSTEM_STATE_SENSORS_READY;├── gyroSetTargetLooptime(pidConfig()-pid_process_denom); // Set the targetLooptime based on the detected gyro sampleRateHz and pid_process_denom├── validateAndFixGyroConfig();├── gyroSetTargetLooptime(pidConfig()-pid_process_denom); // Now reset the targetLooptime as its possible for the validation to change the pid_process_denom├── gyroInitFilters();├── pidInit(currentPidProfile);├── mixerInitProfile();├── USE_PID_AUDIO pidAudioInit();├── USE_SERVOS│ ├── servosInit();│ ├── isMixerUsingServos() servoDevInit(servoConfig()-dev) //pwm_params.useChannelForwarding featureIsEnabled(FEATURE_CHANNEL_FORWARDING);│ └── servosFilterInit();├── USE_PINIO pinioInit(pinioConfig());├── USE_PIN_PULL_UP_DOWN pinPullupPulldownInit();├── USE_PINIOBOX pinioBoxInit(pinioBoxConfig());├── [LED Oprations]├── imuInit();├── failsafeInit();├── rxInit();├── USE_GPS featureIsEnabled(FEATURE_GPS)│ ├── gpsInit();│ └── USE_GPS_RESCUE gpsRescueInit();├── USE_LED_STRIP│ ├── ledStripInit();│ └── featureIsEnabled(FEATURE_LED_STRIP) ledStripEnable();├── USE_ESC_SENSOR featureIsEnabled(FEATURE_ESC_SENSOR) escSensorInit();├── USE_USB_DETECT usbCableDetectInit();├── USE_TRANSPONDER featureIsEnabled(FEATURE_TRANSPONDER)│ ├── transponderInit();│ ├── transponderStartRepeating();│ └── systemState | SYSTEM_STATE_TRANSPONDER_ENABLED;├── USE_FLASH_CHIP !(initFlags FLASH_INIT_ATTEMPTED)│ └── flashInit(flashConfig());initFlags | FLASH_INIT_ATTEMPTED;├── USE_FLASHFS flashfsInit();├── USE_SDCARD dcardConfig()-mode !(initFlags SD_INIT_ATTEMPTED)│ └── sdCardAndFSInit();initFlags | SD_INIT_ATTEMPTED;├── USE_BLACKBOX blackboxInit();├── USE_ACC mixerConfig()-mixerMode MIXER_GIMBAL accStartCalibration();├── gyroStartCalibration(false);├── USE_BARO baroStartCalibration();├── positionInit();├── defined(USE_VTX_COMMON) || defined(USE_VTX_CONTROL) vtxTableInit();├── USE_VTX_CONTROL │ ├── vtxControlInit();│ ├── USE_VTX_COMMON vtxCommonInit();│ ├── USE_VTX_MSP vtxMspInit();│ ├── USE_VTX_SMARTAUDIO vtxSmartAudioInit();│ ├── USE_VTX_TRAMP vtxTrampInit();│ └── USE_VTX_RTC6705 !vtxCommonDevice() useRTC6705 vtxRTC6705Init();├── USE_TIMER timerStart();├── batteryInit(); // always needs doing, regardless of features.├── USE_RCDEVICE rcdeviceInit();├── USE_PERSISTENT_STATS statsInit();├── [Initialize MSP]│ ├── mspInit();│ └── mspSerialInit();├── USE_CMS cmsInit();├── defined(USE_OSD) || (defined(USE_MSP_DISPLAYPORT) defined(USE_CMS)) displayPort_t *osdDisplayPort NULL;├── USE_OSD│ ├── osdDisplayPortDevice_e osdDisplayPortDevice OSD_DISPLAYPORT_DEVICE_NONE;│ └── featureIsEnabled(FEATURE_OSD)│ ├── osdDisplayPortDevice_e device osdConfig()-displayPortDevice;│ ├── case OSD_DISPLAYPORT_DEVICE_AUTO: FALLTHROUGH;│ ├── case OSD_DISPLAYPORT_DEVICE_FRSKYOSD:│ │ ├── osdDisplayPort frskyOsdDisplayPortInit(vcdProfile()-video_system);│ │ └── osdDisplayPort || device OSD_DISPLAYPORT_DEVICE_FRSKYOSD osdDisplayPortDevice OSD_DISPLAYPORT_DEVICE_FRSKYOSD; break;│ ├── case OSD_DISPLAYPORT_DEVICE_MAX7456:│ │ └── max7456DisplayPortInit(vcdProfile(), osdDisplayPort) || device OSD_DISPLAYPORT_DEVICE_MAX7456 osdDisplayPortDevice OSD_DISPLAYPORT_DEVICE_MAX7456;break;│ ├── case OSD_DISPLAYPORT_DEVICE_MSP:│ │ ├── osdDisplayPort displayPortMspInit();│ │ └── osdDisplayPort || device OSD_DISPLAYPORT_DEVICE_MSP osdDisplayPortDevice OSD_DISPLAYPORT_DEVICE_MSP; break;│ ├── case OSD_DISPLAYPORT_DEVICE_NONE:) default:│ ├── osdInit(osdDisplayPort, osdDisplayPortDevice);│ └── osdDisplayPortDevice OSD_DISPLAYPORT_DEVICE_NONE featureDisableImmediate(FEATURE_OSD);├── defined(USE_CMS) defined(USE_MSP_DISPLAYPORT) !osdDisplayPort cmsDisplayPortRegister(displayPortMspInit());├── USE_DASHBOARD featureIsEnabled(FEATURE_DASHBOARD)│ ├── dashboardInit();│ ├── USE_OLED_GPS_DEBUG_PAGE_ONLY dashboardShowFixedPage(PAGE_GPS);│ └── !USE_OLED_GPS_DEBUG_PAGE_ONLY dashboardResetPageCycling();dashboardEnablePageCycling();├── USE_TELEMETRY featureIsEnabled(FEATURE_TELEMETRY) telemetryInit();├── setArmingDisabled(ARMING_DISABLED_BOOT_GRACE_TIME);├── defined(USE_SPI) defined(USE_SPI_DMA_ENABLE_EARLY) spiInitBusDMA();├── USE_MOTOR │ ├── motorPostInit();│ └── motorEnable();├── defined(USE_SPI) defined(USE_SPI_DMA_ENABLE_LATE) !defined(USE_SPI_DMA_ENABLE_EARLY)│ └── spiInitBusDMA();├── debugInit();├── unusedPinsInit();├── tasksInit();└── systemState | SYSTEM_STATE_READY;2.3 run 初始化完成以后我们来理解run运行的过程它主要是一个BetaFlight自研的一个任务调度。 注这个任务调度不会再任务运行过程中途被打断与通常OS系统所描述的任务是不一样的。 run└── loop: scheduler()通俗点的理解 可以认为BetaFlight是在一个bare-metal loop的基础上增加了对业务过程耗时统计基于过程时间优先级调度的一个算法逻辑scheduler。 注后面我们会重点针对BetaFlight自研的调度器进行研读和介绍。
2. 任务调度 系统启动后接下来最为核心的就是任务调度。作为飞控自研的调度器其BetaFlight设计有以下特点 历史遗留问题从性价比开发历程等方面来思考也许不难想象为什么现在是一个基于bare-metal的一个自研任务调度器。业务强耦合鉴于IMU和PID业务对于飞行器飞行来说至关重要因此该调度器在Gyro/Acc/PID的任务调用采用了精准时刻调度(/-0.1us)。任务优先级MCU性能和业务逻辑复杂度在至关重要任务调度之后剩余的时间片可能存在资源不够导致任务“饿死”得不到调度的情况。边缘弹性任务时间优化有限资源 非充分测试 资源可体感设计(OSD/CPU占用率等) 3.1 任务定义 这个结构体是一个优先级和任务配置的相关结构。当然因为BetaFlight自研调度器与飞控应用高度耦合强耦合这只是调度的一部分内容。 typedef struct {// Task static datatask_attribute_t *attribute;// Schedulinguint16_t dynamicPriority; // measurement of how old task was last executed, used to avoid task starvationuint16_t taskAgePeriods;timeDelta_t taskLatestDeltaTimeUs;timeUs_t lastExecutedAtUs; // last time of invocationtimeUs_t lastSignaledAtUs; // time of invocation event for event-driven taskstimeUs_t lastDesiredAt; // time of last desired execution// Statisticsfloat movingAverageCycleTimeUs;timeUs_t anticipatedExecutionTime; // Fixed point expectation of next execution timetimeUs_t movingSumDeltaTime10thUs; // moving sum over 64 samplestimeUs_t movingSumExecutionTime10thUs;timeUs_t maxExecutionTimeUs;timeUs_t totalExecutionTimeUs; // total time consumed by task since boottimeUs_t lastStatsAtUs; // time of last stats gathering for rate calculation #if defined(USE_LATE_TASK_STATISTICS)uint32_t runCount;uint32_t lateCount;timeUs_t execTime; #endif } task_t;3.2 scheduler (调度器) 这就是大名鼎鼎的BetaFlight任务调度器。 scheduler├── gyroEnabled│ ├── [Realtime gyro/filtering/PID tasks get complete priority]│ │ ├── task_t *gyroTask getTask(TASK_GYRO)│ │ ├── nowCycles getCycleCounter()│ │ ├── nextTargetCycles lastTargetCycles desiredPeriodCycles│ │ └── schedLoopRemainingCycles cmpTimeCycles(nextTargetCycles, nowCycles)│ ├── schedLoopRemainingCycles -desiredPeriodCycles //错过了一个desiredPeriodCycles周期导致剩余时间负值且大于一个运行周期│ │ ├── nextTargetCycles desiredPeriodCycles * (1 (schedLoopRemainingCycles / -desiredPeriodCycles)) //常见USB配置工具连接的时候尽力挽救scheduler算法│ │ └── schedLoopRemainingCycles cmpTimeCycles(nextTargetCycles, nowCycles)│ ├── (schedLoopRemainingCycles schedLoopStartMinCycles) (schedLoopStartCycles schedLoopStartMaxCycles)│ │ └── schedLoopStartCycles schedLoopStartDeltaUpCycles│ └── schedLoopRemainingCycles schedLoopStartCycles│ ├── schedLoopStartCycles schedLoopStartMinCycles│ │ └── schedLoopStartCycles - schedLoopStartDeltaDownCycles│ ├── currentTimeUs micros()│ ├── taskExecutionTimeUs schedulerExecuteTask(gyroTask, currentTimeUs)│ ├── gyroFilterReady() taskExecutionTimeUs schedulerExecuteTask(getTask(TASK_FILTER), currentTimeUs)│ ├── pidLoopReady() taskExecutionTimeUs schedulerExecuteTask(getTask(TASK_PID), currentTimeUs)│ ├── rxFrameCheck(currentTimeUs, cmpTimeUs(currentTimeUs, getTask(TASK_RX)-lastExecutedAtUs)) //检查是否有新的RC控制链路数据包收到│ ├── cmp32(millis(), lastFailsafeCheckMs) PERIOD_RXDATA_FAILURE //核查、更新failsafe状态│ ├── lastTargetCycles nextTargetCycles│ ├── gyroDev_t *gyro gyroActiveDev() //获取活跃的gyro设备│ └── [Sync scheduler into lock with gyro] // gyro-gyroModeSPI ! GYRO_EXTI_NO_INT, 这里指数级收敛只要desiredPeriodCycles越精准理论精度会越高│ ├── [Calculate desiredPeriodCycles sampleCycles / GYRO_RATE_COUNT and reset terminalGyroRateCount GYRO_RATE_COUNT]│ └── [Sync lastTargetCycles using exponential normalization by GYRO_RATE_COUNT/GYRO_LOCK_COUNT times iteration]├── nowCycles getCycleCounter();schedLoopRemainingCycles cmpTimeCycles(nextTargetCycles, nowCycles);├── !gyroEnabled || (schedLoopRemainingCycles (int32_t)clockMicrosToCycles(CHECK_GUARD_MARGIN_US))│ ├── currentTimeUs micros()│ ├── for (task_t *task queueFirst(); task ! NULL; task queueNext()) task-attribute-staticPriority ! TASK_PRIORITY_REALTIME //Update task dynamic priorities│ │ ├── task-attribute-checkFunc //有属性检查函数│ │ │ ├── task-dynamicPriority 0│ │ │ │ ├── task-taskAgePeriods 1 (cmpTimeUs(currentTimeUs, task-lastSignaledAtUs) / task-attribute-desiredPeriodUs);│ │ │ │ └── task-dynamicPriority 1 task-attribute-staticPriority * task-taskAgePeriods;│ │ │ ├── task-attribute-checkFunc(currentTimeUs, cmpTimeUs(currentTimeUs, task-lastExecutedAtUs))│ │ │ │ ├── const uint32_t checkFuncExecutionTimeUs cmpTimeUs(micros(), currentTimeUs);│ │ │ │ ├── checkFuncMovingSumExecutionTimeUs checkFuncExecutionTimeUs - checkFuncMovingSumExecutionTimeUs / TASK_STATS_MOVING_SUM_COUNT;│ │ │ │ ├── checkFuncMovingSumDeltaTimeUs task-taskLatestDeltaTimeUs - checkFuncMovingSumDeltaTimeUs / TASK_STATS_MOVING_SUM_COUNT;│ │ │ │ ├── checkFuncTotalExecutionTimeUs checkFuncExecutionTimeUs; // time consumed by scheduler task│ │ │ │ ├── checkFuncMaxExecutionTimeUs MAX(checkFuncMaxExecutionTimeUs, checkFuncExecutionTimeUs)│ │ │ │ ├── task-lastSignaledAtUs currentTimeUs│ │ │ │ ├── task-taskAgePeriods 1│ │ │ │ └── task-dynamicPriority 1 task-attribute-staticPriority│ │ │ └── else│ │ │ └── task-taskAgePeriods 0│ │ ├── !task-attribute-checkFunc //无属性检查函数│ │ │ ├── task-taskAgePeriods (cmpTimeUs(currentTimeUs, task-lastExecutedAtUs) / task-attribute-desiredPeriodUs)│ │ │ └── task-taskAgePeriods 0│ │ │ └── task-dynamicPriority 1 task-attribute-staticPriority * task-taskAgePeriods│ │ └── task-dynamicPriority selectedTaskDynamicPriority│ │ ├── timeDelta_t taskRequiredTimeUs task-anticipatedExecutionTime TASK_EXEC_TIME_SHIFT│ │ ├── int32_t taskRequiredTimeCycles (int32_t)clockMicrosToCycles((uint32_t)taskRequiredTimeUs)│ │ ├── taskRequiredTimeCycles checkCycles taskGuardCycles //增加守护时间预留一些│ │ └── taskRequiredTimeCycles schedLoopRemainingCycles || //剩余时间足够执行任务│ │ (scheduleCount SCHED_TASK_DEFER_MASK) 0 || //???? 这里还不太清楚什么情况│ │ (task - tasks) TASK_SERIAL) //串行任务不阻塞│ │ ├── selectedTaskDynamicPriority task-dynamicPriority;│ │ └── selectedTask task; //选中任务│ ├── checkCycles cmpTimeCycles(getCycleCounter(), nowCycles) //优先级调整以及checkFunc运行需要计算耗时时间│ └── selectedTask│ ├── timeDelta_t taskRequiredTimeUs selectedTask-anticipatedExecutionTime TASK_EXEC_TIME_SHIFT // Recheck the available time as checkCycles is only approximate│ ├── int32_t taskRequiredTimeCycles (int32_t)clockMicrosToCycles((uint32_t)taskRequiredTimeUs)│ ├── nowCycles getCycleCounter()│ ├── schedLoopRemainingCycles cmpTimeCycles(nextTargetCycles, nowCycles)│ ├── !gyroEnabled || (taskRequiredTimeCycles schedLoopRemainingCycles)│ │ ├── uint32_t antipatedEndCycles nowCycles taskRequiredTimeCycles;│ │ ├── taskExecutionTimeUs schedulerExecuteTask(selectedTask, currentTimeUs);│ │ ├── nowCycles getCycleCounter();│ │ ├── int32_t cyclesOverdue cmpTimeCycles(nowCycles, antipatedEndCycles);│ │ ├── (currentTask - tasks) TASK_RX│ │ │ └── skippedRxAttempts 0│ │ ├── (currentTask - tasks) TASK_OSD│ │ │ └── skippedOSDAttempts 0│ │ ├── (cyclesOverdue 0) || (-cyclesOverdue taskGuardMinCycles) //超时但可控在taskGuardMinCycles范围之内│ │ │ └── taskGuardCycles taskGuardMaxCycles│ │ │ └── taskGuardCycles taskGuardDeltaUpCycles //增加守护时间预留更多一些│ │ └── else if (taskGuardCycles taskGuardMinCycles //未超时│ │ └── taskGuardCycles - taskGuardDeltaDownCycles; //减少守护时间│ └── else selectedTask-taskAgePeriods TASK_AGE_EXPEDITE_COUNT) ||│ ((selectedTask - tasks) TASK_OSD) (TASK_AGE_EXPEDITE_OSD ! 0) (skippedOSDAttempts TASK_AGE_EXPEDITE_OSD) ||│ ((selectedTask - tasks) TASK_RX) (TASK_AGE_EXPEDITE_RX ! 0) (skippedRxAttempts TASK_AGE_EXPEDITE_RX)│ └── selectedTask-anticipatedExecutionTime * TASK_AGE_EXPEDITE_SCALE└── scheduleCount;注这里讨论的是不包含UNIT_TEST和USE_LATE_TASK_STATISTICS的代码。
3. 总结 从当前最新4.4.x版本代码上看 BetaFlight整体代码可以分为两部分初始化(init)和运行时(run)应用功能代码已经通过宏定义支持可剪裁编译整个调度器要了解存在一些背景知识需要澄清和讨论已经在附录中整理并正在与开发团队讨论中。。。。
4. 参考资料 【1】BetaFlight开源工程结构简明介绍 【2】BetaFlight开源代码框架简介 【3】BetaFlight深入传感设计传感模块设计框架 【4】BetaFlight统一硬件配置文件研读
5. 附录 – 问题汇总 6.1 Why desiredPeriodCycles is so important to Betaflight task? Let’s say default desiredPeriodCycles is about 8K, which 125us. And the code still check desiredPeriodCycles by GYRO_RATE_COUNT interrupts, what’s the story here? If sample rate is NOT sync with gyro task, there might be dirty/invalid data, is there any bad thing happens if just missed 1 or 2 valid samples? Or this code only tends to logically eliminate this effective data sampling bias? 6.2 What root cause has made gyro task to been overrun, so scheduler has to skip a gyro cycle? As scheduler comments A task has so grossly overrun that at entire gyro cycle has been skipped, especially via USB as the serial. Is there too much serial communication through bf configurator and FC or just USB-VCP code on FC side take a lot of resources? It’ll be the same issue when switching to TTL comunication with FC (suggest test bf-configurator usb_serial convertor FC(UART1 for example)? 6.3 What if serial task is running quite long, which corrupt gyro cycle, is it a problem? As previous discussion on “Why desiredPeriodCycles is so important during Betaflight task?” e.g. use MSP protocol as communication channel with companion computer there are lots of packets, result in long time processing. if this happens, it seems mess up with the gyro cycle, am i right? is there any solution or way to overcome this issue? Code 6.4 What does the condition of “scheduleCount SCHED_TASK_DEFER_MASK 0” stand for in scheduler? Code There are three scenarios for normal(except gyro/acc/pid) tasks to execute: taskRequiredTimeCycles schedLoopRemainingCycles // there is time for task to execute.scheduleCount SCHED_TASK_DEFER_MASK 0 //???(task - tasks) TASK_SERIAL // ok, special case for serial So what’s for case #2 “scheduleCount SCHED_TASK_DEFER_MASK 0”