Hello,
can anyone tell me if the new RaspberryPi4 is capable of hardware timestamping according to IEEE1588/PTP?
Regards
Hello,
can anyone tell me if the new RaspberryPi4 is capable of hardware timestamping according to IEEE1588/PTP?
Regards
On Mon, 29 Jul 2019 00:32:15 -0700 (PDT), snipped-for-privacy@gmail.com declaimed the following:
I highly doubt it... Given the requirements for
Software-based ptpd appears as an option even in Stretch-based Raspbian...
md_admin@microdiversity:~$ apt-cache search ptpd bcrelay - Broadcast relay daemon pptpd - PoPToP Point to Point Tunneling Server ptpd - Precision Time Protocol daemon md_admin@microdiversity:~$
-- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/
It's unclear which ethernet MAC the Pi4 is actually using - we know it uses the Broadcom GENET driver, which is used by some BCM7xxx set top box chips, but as usual with Broadcom we don't get any documentation. The Linux driver is pretty minimal and doesn't do much beyond transferring packets.
Until such time as more data comes out, I don't think we'll be any the wiser.
Theo
I'm sure it can be a slave, it's just a Linux computer, but the Pi (any version) doesn't even have a hardware clock, so probably useless as a ptp master.
There is a battery backed RTC module for the Pi, and a number of people have interfaced to GPS based time signals. So there is no reason why a Pi can't be used for this.
---druck
"With additional hardware and sofware, an Apple II can put a man on the moon"
-- "When a true genius appears in the world, you may know him by this sign, that the dunces are all in confederacy against him."
I wonder how much extra it would add to the purchase price of a Pi to include an RTC powered by a capacitor to keep things going until the Pi has rebooted. If you have a permanent internet connection, it's no problem because as soon as the Pi boots it resyncs with a time source on the internet, but it can be a problem if a Pi is used with an intermittent internet connection.
OK, so we had a very unusual case: no ADSL/VDSL internet connection in our new house for a few weeks, so I was relying on tethering my PC and Pi to the mobile phone internet. That was fine until my Pi rebooted when there was no mobile in range, and its time reset itself to an hour or so earlier. That screwed up the data for my weather station logging that my Pi does: I had to go in and hand-modify the time stamps on some readings until I realised the problem and synced the Pi to NTP.
Given the very portable nature of a Pi, and therefore the chance that it may be used on projects that don't have an internet connection, it needs to be resilient to reboots when it's not able to see an NTP source or when the date/time can't be modified manually.
But maybe an external RTC for those special cases is more cost-effective than adding it to the Pi where it is not needed for situations where there is access to NTP.
Hanging a GPS receiver on it could be a neat solution.
Are there any suitably packaged units and interfacing software available?
-- Martin | martin at Gregorie | gregorie dot org
On Wed, 31 Jul 2019 17:14:59 +0000 (UTC), Martin Gregorie declaimed the following:
-- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/
Thanks for those, especially the first link - that's a goldmine.
-- Martin | martin at Gregorie | gregorie dot org
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