EMAC LL Descriptors

[cbrieske]

I have a few questions related to PTP (IEEE1588) support on the EMAC.

According to the technical reference manual, TDES6 & TDES7 are updated with the timestamp captured for the corresponding transmit frame. What is not clear, is where this timestamp is sourced from.

Is anyone able to shed any light on what timer might be used for this timestamp?

[chuledeco]

Hello, could you finally found the way to implement PTP on ESP32?

[cbrieske]

Unfortunately no. There is an unfortunate lack of information around how to actually enable the timestamping features. Unless i'm missing something obvious, I cant seem to get any timestamps for either TX or RX frames. But I also dont know where the timestamp values are actually derived from. Both of these are key point for actually getting this to work, and I have been unable to get any response from espressif on this subject so far.

I am more than happy to work on porting PTPd, but we really need some input from someone at espressif here!

Its really frustrating, and writes off a whole host of application because they simply haven't fully documented the EMAC.
I'ts annoying that I'm having to look at other MCU's simply because of a lack of documentation.

[ESP_Sprite]

Let me ask the digital team; will get back to you.

Edit: I asked: the PTP uses the internal 80MHz APB clock as a clock source for a 64-bit counter. Can't tell why you can't get anything working out of it, though.

[cbrieske]

Thanks Sprite.

I've only just seen your edit, and haven't spent any more time on this since. Perhaps you can pass the following query along to clear up some of my confusion:

• Can this 64 bit counter be read or set?
• According to the TRM, "When the Advanced Timestamp feature is present" RDES0 Bit 0 indicates the presence of a captured timestamp. Does this mean I need to enable something for the Advanced Timestamp feature to be available?

I would love some information that might point me in the right direction to get this working. I couldn't get any timestamps last time I tried when receiving PTP sync packets.