lwip-ptp

PTPd port for use with lwIP on embedded devices.

IMPORTANT NOTICE!!!

This codebase is not very stable! I am working on a ptpd C++ re-write that should be more stable. However for now, consider this repository more of a code-reference than a working project.

This port is based on PTPv2 release v2rc1, January 2010. In particular, the code is based on ST Microelectronics' AN3411 and the work of mpthompson.

UPDATE Note that stable release V2.1.0 is now being used as a reference.

Since then, the ptpd project structure has changed significantly. The newer versions are much harder to port to a microcontroller, so this project can be considered as a fork from v2rc1 rather than a direct port of the existing project.

Note that the port interface layer is designed to be rollover-safe, but PTPd itself is not yet... ...something to worry about in 2038!

Note that this PTP implementation only uses a fine update method. The coarse update method is not that different to resetting the system time with every sync, so it has been removed from the source.

Prerequisites:

• lwIP is installed and has an architecture port that supports RTOS features such as tasks, mailboxes, queues, etc.

• When PTP is used, the lwipopts.h file should contain the following entry:

#if LWIP_PTP
    #define LWIP_PBUF_CUSTOM_DATA \
                    u32_t tv_sec; \
                    u32_t tv_nsec;
#endif /* LWIP_PTP */

This adds timestamp fields to the basic lwIP pbuf structure.

• All static PTP configuration overrides is done through the lwipopts.h file. All PTP-specific macros start with the prefix LWIP_PTP. Any PTP-specific code in your network driver should be wrapped in the following guard:

#if LWIP_PTP
  // code goes here
#endif /* LWIP_PTP */

this ensures that if LWIP_PTP is defined as 0, all traces of the PTP protocol are removed and lwIP can be used as normal.

• Macros beginning with LWIP_PTP are designed to be set/overridden by the user in lwipopts.h. Macros beginning with __LWIP_PTP are internal, and should not be overriden.

TODO

[x] check the validity of the lwip timers + check for memory allocation issues here!

[ ] management message handling doesn't appear to be implemented in AN3411. Look into this.

[x] If hardware timestamping is used, ptpClock->Outbound/Inbound Latency = 0, but events must wait for a callback

[ ] Document pbuf interface for timestamps

[x] Add OS-specific timer implementation and opts file.

[x] Create document summarising all components required in the driver file.

[ ] see if there is a good way to abstract the actual timer output - this is very hardware-specific.