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Yes, it is. From: "O'Connor, Daniel" In-Reply-To: Date: Mon, 5 Aug 2019 15:28:53 +0930 Cc: "freebsd-arm@FreeBSD.org" , "usb@freebsd.org" Content-Transfer-Encoding: quoted-printable Message-Id: References: To: Ian Lepore X-Mailer: Apple Mail (2.3445.104.11) X-Spam-Score: 0 () No, score=0.0 required=5.0 tests=SPF_HELO_NONE, SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.1 X-Scanned-By: MIMEDefang 2.83 on 10.0.2.1 X-Rspamd-Queue-Id: 4626hg3yzjz4GnF X-Spamd-Bar: ++++++ Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=none (mx1.freebsd.org: domain of darius@dons.net.au has no SPF policy when checking 150.101.137.139) smtp.mailfrom=darius@dons.net.au X-Spamd-Result: default: False [6.19 / 15.00]; TO_DN_EQ_ADDR_SOME(0.00)[]; TO_DN_SOME(0.00)[]; MV_CASE(0.50)[]; HAS_XAW(0.00)[]; RCVD_COUNT_THREE(0.00)[4]; RCVD_NO_TLS_LAST(0.10)[]; RCVD_IN_DNSWL_LOW(-0.10)[139.137.101.150.list.dnswl.org : 127.0.5.1]; IP_SCORE(2.85)[ip: (8.07), ipnet: 150.101.0.0/16(4.31), asn: 4739(1.87), country: AU(0.01)]; R_DKIM_NA(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; SUBJECT_HAS_QUESTION(0.00)[]; ARC_NA(0.00)[]; ASN(0.00)[asn:4739, ipnet:150.101.0.0/16, country:AU]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; NEURAL_SPAM_SHORT(0.95)[0.946,0]; MIME_GOOD(-0.10)[text/plain]; PREVIOUSLY_DELIVERED(0.00)[usb@freebsd.org]; AUTH_NA(1.00)[]; NEURAL_SPAM_MEDIUM(1.00)[0.997,0]; DMARC_NA(0.00)[dons.net.au]; TO_MATCH_ENVRCPT_SOME(0.00)[]; R_SPF_NA(0.00)[]; GREYLIST(0.00)[pass,body] X-Spam: Yes X-BeenThere: freebsd-usb@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FreeBSD support for USB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 05 Aug 2019 06:06:12 -0000 Hi Ian, Firstly, this is a very cool test - thank you for running it :) > On 3 Aug 2019, at 06:46, Ian Lepore wrote: > PPS(2) is an FTDI 232R, a USB 1.1 serial adapter, connected to a port > on a USB 2.0 hub that's connected to a USB 2.0 host port on the > Wandboard. =20 >=20 > PPS(3) is an FTDI 4232H, a USB 2.0 serial adapter, connected to a port > on the same USB hub as PPS(2). =20 > Most people are not worried about their kernel clock being 200 > microseconds off from UTC, even if they're using the PPS signal from a > GPS receiver. So I think most people should feel completely at ease > using a USB serial adapter as the input device for a PPS signal. =20 Does the USB clock derive from the 10MHz Rb clock? If so that would mean = you would see a lot less jitter than a 'normal' user where the USB clock = is not locked too GPS. Do you have a more detailed write up of things like the NTP = configuration file? I think I could replicate your test here although I = have a Beaglebone Black, not a Wanboard so I will need to check if it = can take an external clock. (We have GPS modules & Rb oscillators at = work to create reference clock for bi-static meteor applications). Thanks again. -- Daniel O'Connor "The nice thing about standards is that there are so many of them to choose from." -- Andrew Tanenbaum