Date: Fri, 4 Mar 2016 10:54:14 -0600 From: Karl Denninger <karl@denninger.net> To: freebsd-stable@freebsd.org Subject: Re: PPS input on a generic GPIO pin on Raspberry Pi. Message-ID: <56D9BDB6.6040903@denninger.net> In-Reply-To: <8C90C80B-AC5F-4B12-8E84-84193B8C55C4@pean.org> References: <8C90C80B-AC5F-4B12-8E84-84193B8C55C4@pean.org>
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This is a cryptographically signed message in MIME format. --------------ms020902020602000205010605 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 3/3/2016 12:57, Peter Ankerst=C3=A5l wrote: > Hi! > > I have sort of exactly the same question as Erik: > http://lists.freebsd.org/pipermail/freebsd-questions/2014-July/259055.h= tml > > I have bought a https://learn.adafruit.com/adafruit-ultimate-gps and wa= nt to use the PPS output to discipline my clock. > > But the only source of information on how PPS works in FreeBSD I could = find is this: https://docs.freebsd.org/doc/8.0-RELEASE/usr/share/doc/ntp/= pps.html and it clearly states the two ways to provide a PPS signal. "The= PPS signal can be connected in either of two ways: via the data carrier = detector (DCD) pin of a serial port or via the acknowledge (ACK) pin of a= parallel port=E2=80=9D > > Since the Pi doesn=E2=80=99t have any DCD pin i would like to use a gen= eric GPIO for this. There is a linux kernel module for this: http://lxr.f= ree-electrons.com/source/drivers/pps/clients/pps-gpio.c?v=3D3.6 GPIO is supported on the Pi, I'm using it on 11-Current on my home control software to drive relays on my pool hardware (e.g. valves, heater, VFD motor drive, etc) and it is working very well. I don't believe tapping into that at the kernel level to expose a pps signal (e.g. on /dev/pps or something of the like) would be very difficult at all, since the low-level driver capability is already present. If I get some free time I'll dig around a bit and see if I can cobble something up. It's of some interest to me as well since I have a GPS clock here that currently talks to a serial port on an Intel-based machine and being able to move that to a $35 "appliance" for NTP using the Adafruit setup looks sort of attractive given that the Pi plus the module would be under $100 all-in. --=20 Karl Denninger karl@denninger.net <mailto:karl@denninger.net> /The Market Ticker/ /[S/MIME encrypted email preferred]/ --------------ms020902020602000205010605 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="smime.p7s" Content-Description: S/MIME Cryptographic Signature MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgMFADCABgkqhkiG9w0BBwEAAKCC Bl8wggZbMIIEQ6ADAgECAgEpMA0GCSqGSIb3DQEBCwUAMIGQMQswCQYDVQQGEwJVUzEQMA4G A1UECBMHRmxvcmlkYTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3Rl bXMgTExDMRwwGgYDVQQDExNDdWRhIFN5c3RlbXMgTExDIENBMSIwIAYJKoZIhvcNAQkBFhND dWRhIFN5c3RlbXMgTExDIENBMB4XDTE1MDQyMTAyMjE1OVoXDTIwMDQxOTAyMjE1OVowWjEL MAkGA1UEBhMCVVMxEDAOBgNVBAgTB0Zsb3JpZGExGTAXBgNVBAoTEEN1ZGEgU3lzdGVtcyBM TEMxHjAcBgNVBAMTFUthcmwgRGVubmluZ2VyIChPQ1NQKTCCAiIwDQYJKoZIhvcNAQEBBQAD ggIPADCCAgoCggIBALmEWPhAdphrWd4K5VTvE5pxL3blRQPyGF3ApjUjgtavqU1Y8pbI3Byg XDj2/Uz9Si8XVj/kNbKEjkRh5SsNvx3Fc0oQ1uVjyCq7zC/kctF7yLzQbvWnU4grAPZ3IuAp 3/fFxIVaXpxEdKmyZAVDhk9az+IgHH43rdJRIMzxJ5vqQMb+n2EjadVqiGPbtG9aZEImlq7f IYDTnKyToi23PAnkPwwT+q1IkI2DTvf2jzWrhLR5DTX0fUYC0nxlHWbjgpiapyJWtR7K2YQO aevQb/3vN9gSojT2h+cBem7QIj6U69rEYcEDvPyCMXEV9VcXdcmW42LSRsPvZcBHFkWAJqMZ Myiz4kumaP+s+cIDaXitR/szoqDKGSHM4CPAZV9Yh8asvxQL5uDxz5wvLPgS5yS8K/o7zDR5 vNkMCyfYQuR6PAJxVOk5Arqvj9lfP3JSVapwbr01CoWDBkpuJlKfpQIEeC/pcCBKknllbMYq yHBO2TipLyO5Ocd1nhN/nOsO+C+j31lQHfOMRZaPQykXVPWG5BbhWT7ttX4vy5hOW6yJgeT/ o3apynlp1cEavkQRS8uJHoQszF6KIrQMID/JfySWvVQ4ksnfzwB2lRomrdrwnQ4eG/HBS+0l eozwOJNDIBlAP+hLe8A5oWZgooIIK/SulUAsfI6Sgd8dTZTTYmlhAgMBAAGjgfQwgfEwNwYI KwYBBQUHAQEEKzApMCcGCCsGAQUFBzABhhtodHRwOi8vY3VkYXN5c3RlbXMubmV0Ojg4ODgw CQYDVR0TBAIwADARBglghkgBhvhCAQEEBAMCBaAwCwYDVR0PBAQDAgXgMCwGCWCGSAGG+EIB DQQfFh1PcGVuU1NMIEdlbmVyYXRlZCBDZXJ0aWZpY2F0ZTAdBgNVHQ4EFgQUxRyULenJaFwX RtT79aNmIB/u5VkwHwYDVR0jBBgwFoAUJHGbnYV9/N3dvbDKkpQDofrTbTUwHQYDVR0RBBYw FIESa2FybEBkZW5uaW5nZXIubmV0MA0GCSqGSIb3DQEBCwUAA4ICAQBPf3cYtmKowmGIYsm6 eBinJu7QVWvxi1vqnBz3KE+HapqoIZS8/PolB/hwiY0UAE1RsjBJ7yEjihVRwummSBvkoOyf G30uPn4yg4vbJkR9lTz8d21fPshWETa6DBh2jx2Qf13LZpr3Pj2fTtlu6xMYKzg7cSDgd2bO sJGH/rcvva9Spkx5Vfq0RyOrYph9boshRN3D4tbWgBAcX9POdXCVfJONDxhfBuPHsJ6vEmPb An+XL5Yl26XYFPiODQ+Qbk44Ot1kt9s7oS3dVUrh92Qv0G3J3DF+Vt6C15nED+f+bk4gScu+ JHT7RjEmfa18GT8DcT//D1zEke1Ymhb41JH+GyZchDRWtjxsS5OBFMzrju7d264zJUFtX7iJ 3xvpKN7VcZKNtB6dLShj3v/XDsQVQWXmR/1YKWZ93C3LpRs2Y5nYdn6gEOpL/WfQFThtfnat HNc7fNs5vjotaYpBl5H8+VCautKbGOs219uQbhGZLYTv6okuKcY8W+4EJEtK0xB08vqr9Jd0 FS9MGjQE++GWo+5eQxFt6nUENHbVYnsr6bYPQsZH0CRNycgTG9MwY/UIXOf4W034UpR82TBG 1LiMsYfb8ahQJhs3wdf1nzipIjRwoZKT1vGXh/cj3gwSr64GfenURBxaFZA5O1acOZUjPrRT n3ci4McYW/0WVVA3lDGCBRMwggUPAgEBMIGWMIGQMQswCQYDVQQGEwJVUzEQMA4GA1UECBMH RmxvcmlkYTESMBAGA1UEBxMJTmljZXZpbGxlMRkwFwYDVQQKExBDdWRhIFN5c3RlbXMgTExD MRwwGgYDVQQDExNDdWRhIFN5c3RlbXMgTExDIENBMSIwIAYJKoZIhvcNAQkBFhNDdWRhIFN5 c3RlbXMgTExDIENBAgEpMA0GCWCGSAFlAwQCAwUAoIICTTAYBgkqhkiG9w0BCQMxCwYJKoZI hvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNjAzMDQxNjU0MTRaME8GCSqGSIb3DQEJBDFCBEB5 IIevBW9jxPU9MszKRRynYcgn+v1BnXtCpxb5tvZrQsCHfJKghP5I2vnJb1FeMllFZmVRadq+ Kzo5a/MpOjLFMGwGCSqGSIb3DQEJDzFfMF0wCwYJYIZIAWUDBAEqMAsGCWCGSAFlAwQBAjAK BggqhkiG9w0DBzAOBggqhkiG9w0DAgICAIAwDQYIKoZIhvcNAwICAUAwBwYFKw4DAgcwDQYI KoZIhvcNAwICASgwgacGCSsGAQQBgjcQBDGBmTCBljCBkDELMAkGA1UEBhMCVVMxEDAOBgNV BAgTB0Zsb3JpZGExEjAQBgNVBAcTCU5pY2V2aWxsZTEZMBcGA1UEChMQQ3VkYSBTeXN0ZW1z IExMQzEcMBoGA1UEAxMTQ3VkYSBTeXN0ZW1zIExMQyBDQTEiMCAGCSqGSIb3DQEJARYTQ3Vk YSBTeXN0ZW1zIExMQyBDQQIBKTCBqQYLKoZIhvcNAQkQAgsxgZmggZYwgZAxCzAJBgNVBAYT AlVTMRAwDgYDVQQIEwdGbG9yaWRhMRIwEAYDVQQHEwlOaWNldmlsbGUxGTAXBgNVBAoTEEN1 ZGEgU3lzdGVtcyBMTEMxHDAaBgNVBAMTE0N1ZGEgU3lzdGVtcyBMTEMgQ0ExIjAgBgkqhkiG 9w0BCQEWE0N1ZGEgU3lzdGVtcyBMTEMgQ0ECASkwDQYJKoZIhvcNAQEBBQAEggIAdrDt194x MeX/zfj+scT/Q5h0URy+1n9OkrbqPX1kik/+ECjhHs/9kpDvjz7IawNV8FzB0qrlURJQpTwz yLUFFKiO5nEZQKW7G3fGP6hjLa1H7Am3Fr3kSijEa1bWYeyxHKIByY/fIt98HxiFo8PStTRx ++k7Xa10QVbS5jiz0ROQb0vRJY+4VcT1iLPJ5xblQmLhTlJpk5eKTKCCD2mHeL5chG05HmMD bDIbyEnnlxBE9JvcUouufbWQKOwxcrXFdJjZDx1HEkyI2Wr+6voM7OaQEGGYdAQ40BhvDKSb pfyJ0PlfiGRZ2Rdy6VwQ4oQsUvbQhGwAYAEe+rhZs7sY+LVwR2+Gdd1hCWW7U1swuHiWZUiK VbUvjEwo/VIeSCbt6V+0X8PaJJU+6qXzrBvQ14MOorDkCEId9nskQx5k13L9Jg9OTkd7Q3/P ZUylYimDzWpKcctRL3SMUx/DkNngghBdBVe2JrNprF22gPBO/7tpt/Ewu16W0DKqnLFwFqVD K6TSMLkY6MmOx2JOpDXy1KKuEIYN5gukad/PJYKkFgEvgjzL2G6r3oPFKLDRovewAd/3vZT4 28jSsJqG7qutyB4ACNildEYVdt1mB0xWkwpcX3GtbagtO8NVo0DWrBYh66IE3noqUqfzf25i Jx7RokhZdXJzryHzu/5rL2dnttIAAAAAAAA= --------------ms020902020602000205010605--
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