Date: Sat, 5 Mar 2016 07:54:36 +0100 From: =?utf-8?Q?Peter_Ankerst=C3=A5l?= <peter@pean.org> To: Ian Lepore <ian@freebsd.org> Cc: Karl Denninger <karl@denninger.net>, freebsd-stable@freebsd.org Subject: Re: PPS input on a generic GPIO pin on Raspberry Pi. Message-ID: <EDF36350-65A9-4DB8-886E-6BCD852F2CE6@pean.org> In-Reply-To: <1457114408.13785.150.camel@freebsd.org> References: <8C90C80B-AC5F-4B12-8E84-84193B8C55C4@pean.org> <56D9BDB6.6040903@denninger.net> <1457114408.13785.150.camel@freebsd.org>
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--Apple-Mail-0307F1A2-4FAC-40ED-BC1A-2A8F9D7D194A Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable > On 4 mars 2016, at 19:00, Ian Lepore <ian@freebsd.org> wrote: >=20 >> On Fri, 2016-03-04 at 10:54 -0600, Karl Denninger wrote: >>> On 3/3/2016 12:57, Peter Ankerst=C3=A5l wrote: >>> Hi! >>>=20 >>> I have sort of exactly the same question as Erik: >>> http://lists.freebsd.org/pipermail/freebsd-questions/2014-July/2590 >>> 55.html >>>=20 >>> I have bought a https://learn.adafruit.com/adafruit-ultimate-gps an >>> d want to use the PPS output to discipline my clock. >>>=20 >>> But the only source of information on how PPS works in FreeBSD I >>> could find is this:=20 >>> 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 >>>=20 >>> Since the Pi doesn=C2=B4t have any DCD pin i would like to use a generic= >>> GPIO for this. There is a linux kernel module for this: http://lxr. >>> free-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. >>=20 >> 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 > Don't "cobble something up" just yet... there is "a right way" to fix > this, which is a generic gpio-pps driver. The problem is that it > requires support from the new INTRNG, and the rpi hasn't been converted > to that yet. I'm checking around to see if someone has done the > conversion for rpi and it just hasn't been reveiwed/committed yet; if > not, I guess I'll try to do it myself. >=20 > Writing the actual gpio-pps driver will be pretty quick and easy once > we have the intrng support, I think it'll take me a couple hours. >=20 Oh, so there is hope. Thanks for looking into it.=20 Im not a programmer myself but im willing to help if I can.=20 > Also, FYI, another option with PPS is to use a usb-serial adapter and > feed the PPS in on the CTS or DCD pin. I tested that on rpi a few > months ago and it worked fine. There's surpisingly little jitter even > when the usb bus is heavily loaded with other traffic such as disk or > network IO. >=20 Yes that was going to be my plan B. Good to know that it works. /Peter.=20= --Apple-Mail-0307F1A2-4FAC-40ED-BC1A-2A8F9D7D194A Content-Type: application/pkcs7-signature; name=smime.p7s Content-Disposition: attachment; filename=smime.p7s Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIIGHDCCBhgw ggUAoAMCAQICAwytFTANBgkqhkiG9w0BAQsFADCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0 YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcx ODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENB MB4XDTE1MDEyMDIzMzMxNloXDTE2MDEyMTE5NDgzOVowODEXMBUGA1UEAwwOcGV0ZXJAcGVhbi5v cmcxHTAbBgkqhkiG9w0BCQEWDnBldGVyQHBlYW4ub3JnMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8A MIIBCgKCAQEAwTIUUlN/a5KZCwsiy2W2RmQAuA9utUthnfHU2nrf7KqLx7pPwew/rV//AivhXvU9 SsBSJnDChoZV5w9zWgCZg92hBYtsQ5ocrQZ3nDUwozgrqFb7m5Meda7KoMfYMGb9Zu0XWtwPz2AV fIQA5BhtGQmX08HMAbZkXGZQ8oBF/g7s66OPqDJ/82dkfLagNaPits4zaEhb7Q+pGaa+TkrSXVgH 9Vdlt8t/3izAuQ64ut05NKRZVlljzqIRZB9rPTuSOl6TiViU7Di2s3Im+f1XDv8KmjhgJ/x6rwr/ hS1+PdLgzs64t3i4arkjHAvzzNDUiY8gSK6BKIbAmiJAUPHFjwIDAQABo4IC1DCCAtAwCQYDVR0T BAIwADALBgNVHQ8EBAMCBLAwHQYDVR0lBBYwFAYIKwYBBQUHAwIGCCsGAQUFBwMEMB0GA1UdDgQW BBQ88B0SKeTq4DR77Bl6Whd79uDBMTAfBgNVHSMEGDAWgBRTcu2SnODaywFcfH6WNU7y1LhRgjAZ BgNVHREEEjAQgQ5wZXRlckBwZWFuLm9yZzCCAUwGA1UdIASCAUMwggE/MIIBOwYLKwYBBAGBtTcB AgMwggEqMC4GCCsGAQUFBwIBFiJodHRwOi8vd3d3LnN0YXJ0c3NsLmNvbS9wb2xpY3kucGRmMIH3 BggrBgEFBQcCAjCB6jAnFiBTdGFydENvbSBDZXJ0aWZpY2F0aW9uIEF1dGhvcml0eTADAgEBGoG+ VGhpcyBjZXJ0aWZpY2F0ZSB3YXMgaXNzdWVkIGFjY29yZGluZyB0byB0aGUgQ2xhc3MgMSBWYWxp ZGF0aW9uIHJlcXVpcmVtZW50cyBvZiB0aGUgU3RhcnRDb20gQ0EgcG9saWN5LCByZWxpYW5jZSBv bmx5IGZvciB0aGUgaW50ZW5kZWQgcHVycG9zZSBpbiBjb21wbGlhbmNlIG9mIHRoZSByZWx5aW5n IHBhcnR5IG9ibGlnYXRpb25zLjA2BgNVHR8ELzAtMCugKaAnhiVodHRwOi8vY3JsLnN0YXJ0c3Ns LmNvbS9jcnR1MS1jcmwuY3JsMIGOBggrBgEFBQcBAQSBgTB/MDkGCCsGAQUFBzABhi1odHRwOi8v b2NzcC5zdGFydHNzbC5jb20vc3ViL2NsYXNzMS9jbGllbnQvY2EwQgYIKwYBBQUHMAKGNmh0dHA6 Ly9haWEuc3RhcnRzc2wuY29tL2NlcnRzL3N1Yi5jbGFzczEuY2xpZW50LmNhLmNydDAjBgNVHRIE HDAahhhodHRwOi8vd3d3LnN0YXJ0c3NsLmNvbS8wDQYJKoZIhvcNAQELBQADggEBACJEwwgTiszy cwG0jpVH1tbpXXGIoVOV7WEFqfB0VJ2cWiGUrggnRH4uIjh1LrP1UP0GAARk3UxJZYWdABK8WUXc aowp4UxkPUhlSk1ebuGaxqkntmkL8dz8p5D8Qf9DAgjRX6/5IJuqSSIGpySmVzVS7fMU65MM5SbV l1Qi15t7Bjf/BYdfH/QcUSVE8m0exndVlG7IFMm0GMlxBSH2nAJi+bRhwI3BplZA5XrXCMDMGklB xQuTYc7mZa50mgjtfm5GTSUtJnoD5MP7yd1w26bRXTowEG0H1KPI0iiDyCRF0cZqx0MfryU2EBTg huFZqVmiqJNStdBmRawG4b8CaGExggNvMIIDawIBATCBlDCBjDELMAkGA1UEBhMCSUwxFjAUBgNV BAoTDVN0YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNp Z25pbmcxODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xp ZW50IENBAgMMrRUwCQYFKw4DAhoFAKCCAa8wGAYJKoZIhvcNAQkDMQsGCSqGSIb3DQEHATAcBgkq hkiG9w0BCQUxDxcNMTYwMzA1MDY1NDM2WjAjBgkqhkiG9w0BCQQxFgQUZp1dwpBH8qOGxSlodL7G ULsEywswgaUGCSsGAQQBgjcQBDGBlzCBlDCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0YXJ0 Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcxODA2 BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENBAgMM rRUwgacGCyqGSIb3DQEJEAILMYGXoIGUMIGMMQswCQYDVQQGEwJJTDEWMBQGA1UEChMNU3RhcnRD b20gTHRkLjErMCkGA1UECxMiU2VjdXJlIERpZ2l0YWwgQ2VydGlmaWNhdGUgU2lnbmluZzE4MDYG A1UEAxMvU3RhcnRDb20gQ2xhc3MgMSBQcmltYXJ5IEludGVybWVkaWF0ZSBDbGllbnQgQ0ECAwyt FTANBgkqhkiG9w0BAQEFAASCAQCZHaXmP8VW7PJoPYvrA1cciAu3jMku7koO9kF0Xzm7z+wiv+aM ia19mQQyc0isW3UB3bBuqQNvGQ31HF1U10CdcSCxtLoqaR8aGiJyBxV9uzbCwXRVIqPnyt6nDHIZ +hyNTb6dO9gkECUNC5sLc1miMwkNktTW6qai+vIHqWYGUogVNn1kxwnbXmmPfnjMamg9Ljt+1eM8 MN+Q3fXNZwKF9+Kzv9noGBvCQnqLEzJZX1KX5hXfAwQHYb7oWtYJyb35JnPz46WZgQcxwzIj/I2k ZQG5dpVO46GA6T1wptf20ahZQymI2LC6zGHnexYJGG1c3fYBQfJg1YAVcHfuF/iFAAAAAAAA --Apple-Mail-0307F1A2-4FAC-40ED-BC1A-2A8F9D7D194A--
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