FreeRTOS实现微秒级时间同步(基于1588V2)

本文介绍了基于FreeRTOS+STM32F4平台的PTPD同步协议(基于1588V2)的具体实现

qq_45731845

1066人浏览 · 2025-10-06 21:15:05

qq_45731845 · 2025-10-06 21:15:05 发布

1. 前言

主要是参考了该代码的实现,不过原代码的RTOS用的是RTX5,这里把它移植到了FreeRTOS上,并额外的做了一层抽象方便后续的移植。硬件:STM32F407ZGT6，软件环境: FreeRTOS,ubuntu18, keil5(ARMCC编译器)
原项目链接:
STM32_PTPD
也非常感谢这个博主的博文：
STM32F407移植1588V2
本项目链接:
FreeRTOS_PTPD

2. 项目的代码框架

在把原来的项目中的ptpd部分整合出来后,主要是以下几个文件

ethernetif.c
ethernetif.h
ethptp.c
ethptp.h
network.c
network.h
ptpd.h
ptpd_arch.c
ptpd_arch.h
ptpd_arith.c
ptpd_bmc.c
ptpd_constants.h
ptpd_datatypes.h
ptpd_main.c
ptpd_msg.c
ptpd_net.c
ptpd_protocol.c
ptpd_servo.c
ptpd_time.c
ptpd_timer.c

ethernetif:链接lwip和以太网驱动的核心。在这里把以太网驱动也放到了这个文件中,以及和ptpd协议底层状态记录的相关函数
ethptp: 主要是操作底层ETH外设用来设定时间戳和得到时间戳
network: 更上层的实现,包括LWIP协议栈初始化的封装和ptpd协议初始化的封装,同时定义了一些需要传给LWIP初始化的参数,包括IP地址,MAC地址等
- lwip初始化
- ptpd协议相关的初始化
- mdns协议 / ping协议等辅助的初始化(mdns相关的文件在lwip/apps中)
ptpd.h: 定义了一些DBG调试的宏
ptpd_arch: 对ptpd协议栈用到了进程间通信的IPC的抽象,包括事件标志组,软件定时器等,方便后续适配不同的RTOS平台(个人新增)
ptpd协议栈的代码:在4中进一步的介绍

3. PTPD的核心—时间戳

整个ptpd协议的核心是如何获取到报文发送的精确时间戳,这个不仅仅是协议层的,更需要硬件层提供支持

3.1 硬件层

这里时间戳依赖于硬件的MAC控制器,好在STM32F4底层的MAC控制器支持获取时间戳相关的参数。所以只需要我们在初始化的时候,做好对相关外设的初始化就可以通过ETH_DMA描述来获取时间戳或者修改时间戳了

typedef struct  
{
  __IO uint32_t   Status;           /*!< Status */
  
  uint32_t   ControlBufferSize;     /*!< Control and Buffer1, Buffer2 lengths */
  
  uint32_t   Buffer1Addr;           /*!< Buffer1 address pointer */
  
  uint32_t   Buffer2NextDescAddr;   /*!< Buffer2 or next descriptor address pointer */
  
  /*!< Enhanced ETHERNET DMA PTP Descriptors */
  uint32_t   ExtendedStatus;        /*!< Extended status for PTP receive descriptor */
  
  uint32_t   Reserved1;             /*!< Reserved */
  
  uint32_t   TimeStampLow;          /*!< Time Stamp Low value for transmit and receive */
  
  uint32_t   TimeStampHigh;         /*!< Time Stamp High value for transmit and receive */

} ETH_DMADescTypeDef;

void ETH_EnablePTPTimeStampUpdate(void)
{
  uint32_t tmpreg;

  /* Enable the PTP system time update with the Time Stamp Update register value */
  ETH->PTPTSCR |= ETH_PTPTSCR_TSSTU;

  /* Wait until the write operation will be taken into account :
   at least four TX_CLK/RX_CLK clock cycles */
  tmpreg = ETH->PTPTSCR;
  delay_us(ETH_REG_WRITE_DELAY);
  ETH->PTPTSCR = tmpreg;
}

/**
  * @brief  Initialize the PTP Time Stamp
  * @param  None
  * @retval None
  */
void ETH_InitializePTPTimeStamp(void)
{
  uint32_t tmpreg;

  /* Initialize the PTP Time Stamp */
  ETH->PTPTSCR |= ETH_PTPTSCR_TSSTI;

  /* Wait until the write operation will be taken into account :
   at least four TX_CLK/RX_CLK clock cycles */
  tmpreg = ETH->PTPTSCR;
  delay_us(ETH_REG_WRITE_DELAY);
  ETH->PTPTSCR = tmpreg;
}

另外,PTPD协议栈的实现依赖与mdns服务,所以我们需要配置底层的MAC控制器让它支持mdns协议

 // Initialize custom MAC parameters.
  // NOTE: the MulticastFramesFilter is set to none for support of MDNS packets.
ETH_MACInitTypeDef mac_init;
  memset(&mac_init, 0, sizeof(mac_init));
  mac_init.Watchdog = ETH_WATCHDOG_ENABLE;
  mac_init.Jabber = ETH_JABBER_ENABLE;
  mac_init.InterFrameGap = ETH_INTERFRAMEGAP_96BIT;
  mac_init.CarrierSense = ETH_CARRIERSENCE_ENABLE;
  mac_init.ReceiveOwn = ETH_RECEIVEOWN_ENABLE;
  mac_init.LoopbackMode = ETH_LOOPBACKMODE_DISABLE;
  mac_init.ChecksumOffload = ETH_CHECKSUMOFFLAOD_ENABLE;
  mac_init.RetryTransmission = ETH_RETRYTRANSMISSION_DISABLE;
  mac_init.AutomaticPadCRCStrip = ETH_AUTOMATICPADCRCSTRIP_DISABLE;
  mac_init.BackOffLimit = ETH_BACKOFFLIMIT_10;
  mac_init.DeferralCheck = ETH_DEFFERRALCHECK_DISABLE;
  mac_init.ReceiveAll = ETH_RECEIVEAll_DISABLE;
  mac_init.SourceAddrFilter = ETH_SOURCEADDRFILTER_DISABLE;
  mac_init.PassControlFrames = ETH_PASSCONTROLFRAMES_BLOCKALL;
  mac_init.BroadcastFramesReception = ETH_BROADCASTFRAMESRECEPTION_ENABLE;
  mac_init.DestinationAddrFilter = ETH_DESTINATIONADDRFILTER_NORMAL;
  mac_init.PromiscuousMode = ETH_PROMISCUOUS_MODE_DISABLE;
  mac_init.MulticastFramesFilter = ETH_MULTICASTFRAMESFILTER_NONE;
  mac_init.UnicastFramesFilter = ETH_UNICASTFRAMESFILTER_PERFECT;
  mac_init.HashTableHigh = 0x0U;
  mac_init.HashTableLow = 0x0U;
  mac_init.PauseTime = 0x0U;
  mac_init.ZeroQuantaPause = ETH_ZEROQUANTAPAUSE_DISABLE;
  mac_init.PauseLowThreshold = ETH_PAUSELOWTHRESHOLD_MINUS4;
  mac_init.UnicastPauseFrameDetect = ETH_UNICASTPAUSEFRAMEDETECT_DISABLE;
  mac_init.ReceiveFlowControl = ETH_RECEIVEFLOWCONTROL_DISABLE;
  mac_init.TransmitFlowControl = ETH_TRANSMITFLOWCONTROL_DISABLE;
  mac_init.VLANTagComparison = ETH_VLANTAGCOMPARISON_16BIT;
  mac_init.VLANTagIdentifier = 0x0U;
  HAL_ETH_ConfigMAC(&ethernetif_handle, &mac_init);

3.2 协议层

通过函数ethernetif_get_tx_timestamp可以得到具体的时间戳

// Get the TX time associated with the packet buffer.
void ethernetif_get_tx_timestamp(struct pbuf *p)
{
  // Lock the Ethernet mutex.
   sys_mutex_lock(&ethernetif_mutex_id);

  // Start without a DMA TX descriptor.
  __IO ETH_DMADescTypeDef *dma_tx_desc = NULL;

  // Find the DMA TX descriptor assocated with this packet buffer.
  // This is a onetime function to prevent issues with accidently
  // pointing to a recycled DMA TX descriptor.
  uint32_t index = ethernet_tx_tail;
  while (index != ethernet_tx_head)
  {
    // Is this the DMA TX descriptor we are interested in?
    if (p->time_nsec == ethernet_tx_entries[index].id)
    {
      // Get the DMA TX descriptor for use below.
      dma_tx_desc = ethernet_tx_entries[index].tx_desc;

      // This is a one time operation so clear the entry.
      ethernet_tx_entries[index].id = 0;
      ethernet_tx_entries[index].tx_desc = NULL;

      // We found the DMA TX descriptor.
      break;
    }

    // Increment to the next TX buffer.
    index = (index + 1) == ETH_TXBUFNB ? 0 : index + 1;
  }

  // Release the Ethernet mutex.
  sys_mutex_unlock(&ethernetif_mutex_id);

  // Fill in the default values.
  p->time_sec = 0;
  p->time_nsec = 0;

  // Did we find the dma tx descriptor?
  if (dma_tx_desc)
  {
    // Wait up to 20 millisecond for the DMA transfer to complete.
    for (uint32_t retry_count = 10; (retry_count > 0) && ((dma_tx_desc->Status & ETH_DMATXDESC_TTSS) != ETH_DMATXDESC_TTSS); --retry_count)
    {
      // Wait up to two milliseconds for a transfer to complete.
      EventBits_t xReceivedBits;
      xReceivedBits = sys_eventgroup_wait_bits(&ethernetif_event_id, ETHERNETIF_EVENT_TRANSMIT, 2);
      if (xReceivedBits & ETHERNETIF_EVENT_TRANSMIT)
      {
		break;
      }
    }

    // Make sure after waiting we have the timestamp information.
    if (dma_tx_desc->Status & ETH_DMATXDESC_TTSS )
    {
      // Fill in the timestamp information.
      p->time_sec = dma_tx_desc->TimeStampHigh;
      p->time_nsec = subsecond_to_nanosecond(dma_tx_desc->TimeStampLow);
    }
    else
    {
      // Report timeount.
      printf("ETHERNETIF: tx timestamp timeout\n");
    }
  }
}

得到时间戳的过程可以大概简化为:

底层调用netif->linkouput发送数据包,如果数据包是PTPD协议相关的,就记录以太网的描述符和pbuf之间的映射关系(这里对pbuf做了一定的修改,新增了时间戳变量成员)
当以太网发送完成后,会调用对应的回调函数,此时回调函数会对事件标志组进行置位操作

// Ethernet Tx transfer complete callback from the HAL.
void HAL_ETH_TxCpltCallback(ETH_HandleTypeDef *eth_handle)
{
  UNUSED(eth_handle);
	BaseType_t xHigherPriorityTaskWoken = pdFALSE;
  // Notify the Ethernet thread of the outgoing packet complete.
  xHigherPriorityTaskWoken = sys_eventgroup_set_bits_isr(&ethernetif_event_id, ETHERNETIF_EVENT_TRANSMIT); 
	if( xHigherPriorityTaskWoken != pdFALSE )
  {
    portYIELD_FROM_ISR( xHigherPriorityTaskWoken );
  }
}

ethernetif_get_tx_timestamp就可以等到这个标志位置位,从而从对应的以太网描述符中取出时间进行记录

4.PTPD其它文件的简介

具体的实现我看的也不深,权当是做了个了解

4.1 ptpd_net.c : 在应用层与LWIP协议栈交互
- ptpd_net_init函数
  初始化两个消息队列
- 创建了两个udp控制块
  - 事件端口的控制块 eventPcb: 319端口控制事件消息(Sync同步 Delay_seq(延迟请求))
    需要加时间戳的消息
  - 通用端口控制块 generalPcb: 320端口辅助同步的消息
    不需要加时间戳的消息
- 事件端口的接收回调 : ptpd_net_event_callback
  把pbuf放入事件队列eventQ并唤醒处理线程
- 通用端口的接收回调 : ptpd_net_general_callback
  把pbuf放入通用事件队列generalQ,并唤醒处理线程(ptpd_main当中)
- ptpd发送数据 ptpd_net_send函数:
  通过对应的udp控制块发送数据然后如果需要返回时间戳的会把具体发送时刻通过指针返回
```
if (time != NULL)
{
    // We have special call back into the Ethernet interface to fill the timestamp
    // of the buffer just transmitted. This call will block for up to a certain amount
    // of time before it may fail if a timestamp was not obtained.
    ethernetif_get_tx_timestamp(p);
}
// Get the timestamp of the sent buffer.  We avoid overwriting 
// the time if it looks to be an invalid zero value.
if ((time != NULL) && (p->time_sec != 0))
{
    time->seconds = p->time_sec;
    time->nanoseconds = p->time_nsec;
    DBGV("PTPD: %d sec %d nsec\n", time->seconds, time->nanoseconds);
}
```
- ptpd真正接收数据
```
/*从对应队列取出数据并处理*/
static ssize_t ptpd_net_recv(octet_t *buf, TimeInternal *time, BufQueue *queue)
```
  把数据从queue中取出来数据信息放在buf里时间信息放在TimeInternal, 时间信息来自以太网的DMA描述符

4.2 ptpd_protocol.c: 协议实现的核心

ptpd_protocol_to_state : 状态机状态切换
ptpd_protocol_do_state: 处理事件调用 do_state进行状态切换

handle: 协议事件处理的核心

step1: 把数据从消息队列取出来

step2: switch - case 处理 : 根据不同报文的类型去做处理

 switch (ptp_clock->msgTmpHeader.messageType)
{
    case ANNOUNCE:
    handle_announce(ptp_clock, is_from_self);
    break;

    case SYNC:
    handle_sync(ptp_clock, &time, is_from_self);
    break;

    case FOLLOW_UP:
    handle_follow_up(ptp_clock, is_from_self);
    break;

    case DELAY_REQ:
    handle_delay_req(ptp_clock, &time, is_from_self);
    break;

    case PDELAY_REQ:
    handle_peer_delay_req(ptp_clock, &time, is_from_self);
    ...
}

4.3 ptpd_sero
ptpd的算法部分包括如何计算同步时间还有一些滤波操作在这里面
- ptpd_aritch.c: 辅助数学函数
- ptpd_bmc.c : 最佳主时钟（BMC）算法核心作为丛机用不到
4.4 ptpd_time 与 ethptp: ptpd算法得到时间后对于底层的修正
修正以太网的ETH寄存器相关的标志位
ptpd_get_rand无用正好也没随机数寄存器删了就行
4.5 ptpd_msg
中间层就是涉及到某些帧具体是怎么封装了(delay_req / Sync / follow_up) 需要适配的话得改这里—根据不同的实现进行修改
4.6 ptpd_timer.c:
涉及到一些ptpd协议中用到的软件定时器,是为了辅助前面提到的ptpd_protocol,进行一些超时的处理
4.7 ptpd_main.c:
没啥好讲的就是调用封装的prptocol的API 以及提供一些对外的接口来得到ptpd协议栈的信息
为什么底层用udp不用tcp
可能是因为udp的mudp多播吧把自己报文广播给特定的主机
包括udp的传输效率更高

5 使用与测试

首先要保证你的ubutnu和你的开发板在一个子网下
ubutun上要安装一个ptpd4l，然后启动协议，我这里是ens33网卡,根据具体情况进行修改

sudo ptp4l -E -4 -S -i ens33 -m

最终的结果为

handle: ptpd_net_recv_event returned 44
handle: unpacked message type 0
handle_sync: received in state PTP_LISTENING
handle_sync: disreguard
handle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 44
handle: unpacked message type 8
handle_followup: received in state PTP_LISTENING
handle_followup: disreguard
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 64
handle: unpacked message type 11
handle_announce: received in state PTP_LISTENING
handle_announce: from another foreign master
event STATE_DECISION_EVENT
recommending state PTP_SLAVE
leaving state PTP_LISTENING
ptpd_servo_init_clock
entering state PTP_UNCALIBRATED
PTPD: entering UNCALIBRATED statehandle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 44
handle: unpacked message type 8
handle_followup: received in state PTP_UNCALIBRATED
handle_followup: not waiting a message
event MASTER_CLOCK_CHANGED
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: something
handle: ptpd_net_recv_event returned 44
handle: unpacked message type 0
handle_sync: received in state PTP_UNCALIBRATED
handle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 44
handle: unpacked message type 8
handle_followup: received in state PTP_UNCALIBRATED
ptpd_servo_update_offset
ptpd_servo_update_offset: offset -1759720361 seconds -340254876 nanoseconds
ptpd_servo_update_offset: cannot filter seconds
PTPD: ptpd_servo_update_clock offset -1759720361 sec 340254876 nsec
ptpd_servo_init_clock
PTPD: ptpd_servo_update_clock: one-way delay averaged (E2E): 0 sec 0 nsec
PTPD: ptpd_servo_update_clock: offset from master: -1759720361 sec -340254876 nsec
PTPD: ptpd_servo_update_clock: observed drift: 0
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 64
handle: unpacked message type 11
handle_announce: received in state PTP_UNCALIBRATED
event STATE_DECISION_EVENT
recommending state PTP_SLAVE
handle: something
handle: ptpd_net_recv_event returned 44
handle: unpacked message type 0
handle_sync: received in state PTP_UNCALIBRATED
handle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 44
handle: unpacked message type 8
handle_followup: received in state PTP_UNCALIBRATED
ptpd_servo_update_offset
ptpd_servo_update_offset: offset 0 seconds -76817 nanoseconds
PTPD: filter: -76817 -> -76817 (0)
PTPD: ptpd_servo_update_clock offset 0 sec 76817 nsec
PTPD: ptpd_servo_update_clock: one-way delay averaged (E2E): 0 sec 0 nsec
PTPD: ptpd_servo_update_clock: offset from master: 0 sec -76817 nsec
PTPD: ptpd_servo_update_clock: observed drift: -4801
event MASTER_CLOCK_SELECTED
leaving state PTP_UNCALIBRATED
entering state PTP_SLAVE
PTPD: entering SLAVE statehandle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 0
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: something
handle: ptpd_net_recv_event returned 44
handle: unpacked message type 0
handle_sync: received in state PTP_SLAVE
handle: something
handle: ptpd_net_recv_event returned 0
handle: ptpd_net_recv_general returned 44
handle: unpacked message type 8
handle_followup: received in state PTP_SLAVE
ptpd_servo_update_offset
ptpd_servo_update_offset: offset 0 seconds -44237 nanoseconds
PTPD: filter: -44237 -> -60527 (1)
PTPD: ptpd_servo_update_clock offset 0 sec 60527 nsec
PTPD: ptpd_servo_update_clock: one-way delay averaged (E2E): 0 sec 0 nsec
PTPD: ptpd_servo_update_clock: offset from master: 0 sec -60527 nsec
PTPD: ptpd_servo_update_clock: observed drift: -8583
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: nothing
handle: something

从结果来看,大概是几十微妙,emmm客观来说这个结果算不上太优秀,想要更请准的结果可以修改对应的宏

#define DEFAULT_CALIBRATED_OFFSET_NS    10000    // Offset from master < 10us -> calibrated
#define DEFAULT_UNCALIBRATED_OFFSET_NS  100000   // Offset from master > 100us -> uncalibrated
#define MAX_ADJ_OFFSET_NS               100000000  // Max offset to try to adjust it < 100ms