想在项目中实现 PTP 精确时钟协议功能。选用 STM32H745 的原因是该芯片以太网 MAC 内置硬件 PTP 模块，支持硬件时间戳卸载。
研读参考手册后编写了如下初始化代码：
uint32_t SubSecondValue = 43;
#define ADJ_FREQ_BASE_ADDEND 0x35455A81
// Mask the Timestamp Trigger interrupt by clearing bit 12 of Interrupt enable register (ETH_MACIER).
heth->Instance->MACIER &= ~(ETH_MACIER_TSIE);
// Set bit 0 of Timestamp control Register (ETH_MACTSCR) to enable timestamping.
//heth->Instance->MACTSCR |= 1; // Done at the END! :)
//Program Subsecond increment register (ETH_MACSSIR) based on the PTP clock frequency.
heth->Instance->MACSSIR = (SubSecondValue<<16);
// if you use the Fine Correction method, program Timestamp addend register (ETH_MACTSAR) and set bit 5 of Timestamp control Register (ETH_MACTSCR)
heth->Instance->MACTSAR = ADJ_FREQ_BASE_ADDEND;
heth->Instance->MACTSCR |= ETH_MACTSCR_TSADDREG;
/* Poll the Time stamp control register until bit 5 is cleared. */
while(ETH_GetPTPFlagStatus(heth, ETH_PTP_FLAG_TSARU) == SET);
/* Enable the PTP Fine Update method Fine*/
heth->Instance->MACTSCR |= ETH_MACTSCR_TSCFUPDT;
/* Program the Time stamp high update and Time stamp low update registers
* with the appropriate time value. */
/* Set the PTP Time Update High Register */
heth->Instance->MACSTSUR = 0;
/* Set the PTP Time Update Low Register with sign */
heth->Instance->MACSTNUR = ETH_PTP_PositiveTime | 0;
/* Set Time stamp control register bit 2 (Time stamp init). */
heth->Instance->MACTSCR |= ETH_MACTSCR_TSINIT;
/* Set PPS frequency to 128 Hz */
heth->Instance->MACPPSCR = 7;
// Source: RM0399 Page 3039
// 1. Program SNAPTYPSEL, TSMSTRENA and TSEVNTENA fields of Timestamp control Register (ETH_MACTSCR) to 0, 0, and 1 respectively.
heth->Instance->MACTSCR &= ~((0b00)<<16); // Clear SNAPTYPSEL
heth->Instance->MACTSCR &= ~((0b0)<<15); // Clear TSMSTRENA
heth->Instance->MACTSCR |= (1 << 14); // Set TSEVNTENA
// 2. Program the PTOEN bit and DN field of PTP Offload control register (ETH_MACPOCR) to enable PTP Offload feature and domain Number to match with ingress PTP Sync message and send in egress PTP Delay_Req message.
heth->Instance->MACPOCR &= ~((0b00000000)<<8); // Set Domain number to 0
heth->Instance->MACPOCR |= 4; // Set APDREQEN
// 3. Program the 80-bit Source Port Identity in PTP Source Port Identity 0 Register (ETH_MACSPI0R), PTP Source port identity 1 register (ETH_MACSPI1R) and PTP Source port identity 2 register (ETH_MACSPI2R) to match with ingress PTP Sync message and send in egress PTP Delay_Req message.
heth->Instance->MACSPI0R = 0x57ffec79;
heth->Instance->MACSPI1R = 0xfe81d0c8;
heth->Instance->MACSPI2R = 0x0001;
// 4. Program the DRSYNCR field in Log message interval register (ETH_MACLMIR) to indicate one PTP Delay_Req message is generated in response to how many received PTP Sync messages.
heth->Instance->MACLMIR |= (2<<24);
heth->Instance->MACPOCR |= 1; // Set PTOEN
这段代码在以太网底层初始化low_level_init函数返回前执行。
开发目标是实现 PTP 从设备，依靠硬件卸载机制自动响应主时钟的 PTP 报文、同步硬件内部时间计数器，尽量减少软件干预。
遇到的问题是Wireshark 抓包看不到 STM32 向 PTP 主时钟发出任何报文；外部专用 PTP 主时钟设备正常持续发送 SYNC、Follow Up 报文。请问代码哪里存在错误？
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