€•ÛŒ      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ"/translations/zh_CN/driver-api/pps”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ"/translations/zh_TW/driver-api/pps”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ"/translations/it_IT/driver-api/pps”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ"/translations/ja_JP/driver-api/pps”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ"/translations/ko_KR/driver-api/pps”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ"/translations/sp_SP/driver-api/pps”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒcomment”“”)”}”(hŒ SPDX-License-Identifier: GPL-2.0”h]”hŒ SPDX-License-Identifier: GPL-2.0”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒ</var/lib/git/docbuild/linux/Documentation/driver-api/pps.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒPPS - Pulse Per Second”h]”hŒPPS - Pulse Per Second”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h KubhŒ	paragraph”“”)”}”(hŒ;Copyright (C) 2007 Rodolfo Giometti <giometti@enneenne.com>”h]”(hŒ%Copyright (C) 2007 Rodolfo Giometti <”…””}”(hhËhžhhŸNh NubhŒ	reference”“”)”}”(hŒgiometti@enneenne.com”h]”hŒgiometti@enneenne.com”…””}”(hhÕhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:giometti@enneenne.com”uh1hÓhhËubhŒ>”…””}”(hhËhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhÊ)”}”(hŒïThis program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.”h]”hŒïThis program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.”…””}”(hhïhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K	hh¶hžhubhÊ)”}”(hŒéThis program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.”h]”hŒéThis program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.”…””}”(hhýhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khh¶hžhubhµ)”}”(hhh]”(hº)”}”(hŒOverview”h]”hŒOverview”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj  hžhhŸh³h KubhÊ)”}”(hŒ\LinuxPPS provides a programming interface (API) to define in the
system several PPS sources.”h]”hŒ\LinuxPPS provides a programming interface (API) to define in the
system several PPS sources.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj  hžhubhÊ)”}”(hŒ°PPS means "pulse per second" and a PPS source is just a device which
provides a high precision signal each second so that an application
can use it to adjust system clock time.”h]”hŒ´PPS means â€œpulse per secondâ€ and a PPS source is just a device which
provides a high precision signal each second so that an application
can use it to adjust system clock time.”…””}”(hj*  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj  hžhubhÊ)”}”(hX/  A PPS source can be connected to a serial port (usually to the Data
Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
CPU's GPIOs (this is the common case in embedded systems) but in each
case when a new pulse arrives the system must apply to it a timestamp
and record it for userland.”h]”hX1  A PPS source can be connected to a serial port (usually to the Data
Carrier Detect pin) or to a parallel port (ACK-pin) or to a special
CPUâ€™s GPIOs (this is the common case in embedded systems) but in each
case when a new pulse arrives the system must apply to it a timestamp
and record it for userland.”…””}”(hj8  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj  hžhubhÊ)”}”(hŒ©Common use is the combination of the NTPD as userland program, with a
GPS receiver as PPS source, to obtain a wallclock-time with
sub-millisecond synchronisation to UTC.”h]”hŒ©Common use is the combination of the NTPD as userland program, with a
GPS receiver as PPS source, to obtain a wallclock-time with
sub-millisecond synchronisation to UTC.”…””}”(hjF  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K%hj  hžhubeh}”(h]”Œoverview”ah ]”h"]”Œoverview”ah$]”h&]”uh1h´hh¶hžhhŸh³h Kubhµ)”}”(hhh]”(hº)”}”(hŒRFC considerations”h]”hŒRFC considerations”…””}”(hj_  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj\  hžhhŸh³h K+ubhÊ)”}”(hŒ“While implementing a PPS API as RFC 2783 defines and using an embedded
CPU GPIO-Pin as physical link to the signal, I encountered a deeper
problem:”h]”hŒ“While implementing a PPS API as RFC 2783 defines and using an embedded
CPU GPIO-Pin as physical link to the signal, I encountered a deeper
problem:”…””}”(hjm  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K-hj\  hžhubhŒblock_quote”“”)”}”(hŒVAt startup it needs a file descriptor as argument for the function
time_pps_create().
”h]”hÊ)”}”(hŒUAt startup it needs a file descriptor as argument for the function
time_pps_create().”h]”hŒUAt startup it needs a file descriptor as argument for the function
time_pps_create().”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K1hj}  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j{  hŸh³h K1hj\  hžhubhÊ)”}”(hX¼  This implies that the source has a /dev/... entry. This assumption is
OK for the serial and parallel port, where you can do something
useful besides(!) the gathering of timestamps as it is the central
task for a PPS API. But this assumption does not work for a single
purpose GPIO line. In this case even basic file-related functionality
(like read() and write()) makes no sense at all and should not be a
precondition for the use of a PPS API.”h]”hX¼  This implies that the source has a /dev/... entry. This assumption is
OK for the serial and parallel port, where you can do something
useful besides(!) the gathering of timestamps as it is the central
task for a PPS API. But this assumption does not work for a single
purpose GPIO line. In this case even basic file-related functionality
(like read() and write()) makes no sense at all and should not be a
precondition for the use of a PPS API.”…””}”(hj•  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K4hj\  hžhubhÊ)”}”(hŒrThe problem can be simply solved if you consider that a PPS source is
not always connected with a GPS data source.”h]”hŒrThe problem can be simply solved if you consider that a PPS source is
not always connected with a GPS data source.”…””}”(hj£  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K<hj\  hžhubhÊ)”}”(hŒ½So your programs should check if the GPS data source (the serial port
for instance) is a PPS source too, and if not they should provide the
possibility to open another device as PPS source.”h]”hŒ½So your programs should check if the GPS data source (the serial port
for instance) is a PPS source too, and if not they should provide the
possibility to open another device as PPS source.”…””}”(hj±  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K?hj\  hžhubhÊ)”}”(hŒhIn LinuxPPS the PPS sources are simply char devices usually mapped
into files /dev/pps0, /dev/pps1, etc.”h]”hŒhIn LinuxPPS the PPS sources are simply char devices usually mapped
into files /dev/pps0, /dev/pps1, etc.”…””}”(hj¿  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KChj\  hžhubeh}”(h]”Œrfc-considerations”ah ]”h"]”Œrfc considerations”ah$]”h&]”uh1h´hh¶hžhhŸh³h K+ubhµ)”}”(hhh]”(hº)”}”(hŒPPS with USB to serial devices”h]”hŒPPS with USB to serial devices”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjÕ  hžhhŸh³h KHubhÊ)”}”(hX<  It is possible to grab the PPS from an USB to serial device. However,
you should take into account the latencies and jitter introduced by
the USB stack. Users have reported clock instability around +-1ms when
synchronized with PPS through USB. With USB 2.0, jitter may decrease
down to the order of 125 microseconds.”h]”hX<  It is possible to grab the PPS from an USB to serial device. However,
you should take into account the latencies and jitter introduced by
the USB stack. Users have reported clock instability around +-1ms when
synchronized with PPS through USB. With USB 2.0, jitter may decrease
down to the order of 125 microseconds.”…””}”(hjæ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KJhjÕ  hžhubhÊ)”}”(hŒjThis may be suitable for time server synchronization with NTP because
of its undersampling and algorithms.”h]”hŒjThis may be suitable for time server synchronization with NTP because
of its undersampling and algorithms.”…””}”(hjô  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KPhjÕ  hžhubhÊ)”}”(hŒêIf your device doesn't report PPS, you can check that the feature is
supported by its driver. Most of the time, you only need to add a call
to usb_serial_handle_dcd_change after checking the DCD status (see
ch341 and pl2303 examples).”h]”hŒìIf your device doesnâ€™t report PPS, you can check that the feature is
supported by its driver. Most of the time, you only need to add a call
to usb_serial_handle_dcd_change after checking the DCD status (see
ch341 and pl2303 examples).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KShjÕ  hžhubeh}”(h]”Œpps-with-usb-to-serial-devices”ah ]”h"]”Œpps with usb to serial devices”ah$]”h&]”uh1h´hh¶hžhhŸh³h KHubhµ)”}”(hhh]”(hº)”}”(hŒCoding example”h]”hŒCoding example”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj  hžhhŸh³h KZubhÊ)”}”(hŒ`To register a PPS source into the kernel you should define a struct
pps_source_info as follows::”h]”hŒ_To register a PPS source into the kernel you should define a struct
pps_source_info as follows:”…””}”(hj)  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K\hj  hžhubhŒliteral_block”“”)”}”(hX_  static struct pps_source_info pps_ktimer_info = {
        .name         = "ktimer",
        .path         = "",
        .mode         = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
                        PPS_ECHOASSERT |
                        PPS_CANWAIT | PPS_TSFMT_TSPEC,
        .echo         = pps_ktimer_echo,
        .owner        = THIS_MODULE,
};”h]”hX_  static struct pps_source_info pps_ktimer_info = {
        .name         = "ktimer",
        .path         = "",
        .mode         = PPS_CAPTUREASSERT | PPS_OFFSETASSERT |
                        PPS_ECHOASSERT |
                        PPS_CANWAIT | PPS_TSFMT_TSPEC,
        .echo         = pps_ktimer_echo,
        .owner        = THIS_MODULE,
};”…””}”hj9  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h K_hj  hžhubhÊ)”}”(hŒ_and then calling the function pps_register_source() in your
initialization routine as follows::”h]”hŒ^and then calling the function pps_register_source() in your
initialization routine as follows:”…””}”(hjG  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Kihj  hžhubj8  )”}”(hŒisource = pps_register_source(&pps_ktimer_info,
                    PPS_CAPTUREASSERT | PPS_OFFSETASSERT);”h]”hŒisource = pps_register_source(&pps_ktimer_info,
                    PPS_CAPTUREASSERT | PPS_OFFSETASSERT);”…””}”hjU  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h Klhj  hžhubhÊ)”}”(hŒ(The pps_register_source() prototype is::”h]”hŒ'The pps_register_source() prototype is:”…””}”(hjc  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Kohj  hžhubj8  )”}”(hŒIint pps_register_source(struct pps_source_info *info, int default_params)”h]”hŒIint pps_register_source(struct pps_source_info *info, int default_params)”…””}”hjq  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h Kqhj  hžhubhÊ)”}”(hXC  where "info" is a pointer to a structure that describes a particular
PPS source, "default_params" tells the system what the initial default
parameters for the device should be (it is obvious that these parameters
must be a subset of ones defined in the struct
pps_source_info which describe the capabilities of the driver).”h]”hXK  where â€œinfoâ€ is a pointer to a structure that describes a particular
PPS source, â€œdefault_paramsâ€ tells the system what the initial default
parameters for the device should be (it is obvious that these parameters
must be a subset of ones defined in the struct
pps_source_info which describe the capabilities of the driver).”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Kshj  hžhubhÊ)”}”(hŒ”Once you have registered a new PPS source into the system you can
signal an assert event (for example in the interrupt handler routine)
just using::”h]”hŒ“Once you have registered a new PPS source into the system you can
signal an assert event (for example in the interrupt handler routine)
just using:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Kyhj  hžhubj8  )”}”(hŒ.pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)”h]”hŒ.pps_event(source, &ts, PPS_CAPTUREASSERT, ptr)”…””}”hj›  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h K}hj  hžhubhÊ)”}”(hŒ$where "ts" is the event's timestamp.”h]”hŒ*where â€œtsâ€ is the eventâ€™s timestamp.”…””}”(hj©  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj  hžhubhÊ)”}”(hŒ‘The same function may also run the defined echo function
(pps_ktimer_echo(), passing to it the "ptr" pointer) if the user
asked for that... etc..”h]”hŒ•The same function may also run the defined echo function
(pps_ktimer_echo(), passing to it the â€œptrâ€ pointer) if the user
asked for that... etc..”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Khj  hžhubhÊ)”}”(hŒFPlease see the file drivers/pps/clients/pps-ktimer.c for example code.”h]”hŒFPlease see the file drivers/pps/clients/pps-ktimer.c for example code.”…””}”(hjÅ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K…hj  hžhubeh}”(h]”Œcoding-example”ah ]”h"]”Œcoding example”ah$]”h&]”uh1h´hh¶hžhhŸh³h KZubhµ)”}”(hhh]”(hº)”}”(hŒSYSFS support”h]”hŒSYSFS support”…””}”(hjÞ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjÛ  hžhhŸh³h K‰ubhÊ)”}”(hŒJIf the SYSFS filesystem is enabled in the kernel it provides a new class::”h]”hŒIIf the SYSFS filesystem is enabled in the kernel it provides a new class:”…””}”(hjì  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K‹hjÛ  hžhubj8  )”}”(hŒ($ ls /sys/class/pps/
pps0/  pps1/  pps2/”h]”hŒ($ ls /sys/class/pps/
pps0/  pps1/  pps2/”…””}”hjú  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h KhjÛ  hžhubhÊ)”}”(hŒdEvery directory is the ID of a PPS sources defined in the system and
inside you find several files::”h]”hŒcEvery directory is the ID of a PPS sources defined in the system and
inside you find several files:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KhjÛ  hžhubj8  )”}”(hŒ†$ ls -F /sys/class/pps/pps0/
assert     dev        mode       path       subsystem@
clear      echo       name       power/     uevent”h]”hŒ†$ ls -F /sys/class/pps/pps0/
assert     dev        mode       path       subsystem@
clear      echo       name       power/     uevent”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h K“hjÛ  hžhubhÊ)”}”(hŒXInside each "assert" and "clear" file you can find the timestamp and a
sequence number::”h]”hŒ_Inside each â€œassertâ€ and â€œclearâ€ file you can find the timestamp and a
sequence number:”…””}”(hj$  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K˜hjÛ  hžhubj8  )”}”(hŒ7$ cat /sys/class/pps/pps0/assert
1170026870.983207967#8”h]”hŒ7$ cat /sys/class/pps/pps0/assert
1170026870.983207967#8”…””}”hj2  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h K›hjÛ  hžhubhÊ)”}”(hŒcWhere before the "#" is the timestamp in seconds; after it is the
sequence number. Other files are:”h]”hŒgWhere before the â€œ#â€ is the timestamp in seconds; after it is the
sequence number. Other files are:”…””}”(hj@  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KžhjÛ  hžhubj|  )”}”(hX  * echo: reports if the PPS source has an echo function or not;

* mode: reports available PPS functioning modes;

* name: reports the PPS source's name;

* path: reports the PPS source's device path, that is the device the
  PPS source is connected to (if it exists).

”h]”hŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒ=echo: reports if the PPS source has an echo function or not;
”h]”hÊ)”}”(hŒ<echo: reports if the PPS source has an echo function or not;”h]”hŒ<echo: reports if the PPS source has an echo function or not;”…””}”(hj]  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K¡hjY  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jW  hjT  ubjX  )”}”(hŒ/mode: reports available PPS functioning modes;
”h]”hÊ)”}”(hŒ.mode: reports available PPS functioning modes;”h]”hŒ.mode: reports available PPS functioning modes;”…””}”(hju  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K£hjq  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jW  hjT  ubjX  )”}”(hŒ%name: reports the PPS source's name;
”h]”hÊ)”}”(hŒ$name: reports the PPS source's name;”h]”hŒ&name: reports the PPS sourceâ€™s name;”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K¥hj‰  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jW  hjT  ubjX  )”}”(hŒopath: reports the PPS source's device path, that is the device the
PPS source is connected to (if it exists).

”h]”hÊ)”}”(hŒmpath: reports the PPS source's device path, that is the device the
PPS source is connected to (if it exists).”h]”hŒopath: reports the PPS sourceâ€™s device path, that is the device the
PPS source is connected to (if it exists).”…””}”(hj¥  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K§hj¡  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jW  hjT  ubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ*”uh1jR  hŸh³h K¡hjN  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j{  hŸh³h K¡hjÛ  hžhubeh}”(h]”Œsysfs-support”ah ]”h"]”Œsysfs support”ah$]”h&]”uh1h´hh¶hžhhŸh³h K‰ubhµ)”}”(hhh]”(hº)”}”(hŒTesting the PPS support”h]”hŒTesting the PPS support”…””}”(hjÒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjÏ  hžhhŸh³h K¬ubhÊ)”}”(hX&  In order to test the PPS support even without specific hardware you can use
the pps-ktimer driver (see the client subsection in the PPS configuration menu)
and the userland tools available in your distribution's pps-tools package,
http://linuxpps.org , or https://github.com/redlab-i/pps-tools.”h]”(hŒéIn order to test the PPS support even without specific hardware you can use
the pps-ktimer driver (see the client subsection in the PPS configuration menu)
and the userland tools available in your distributionâ€™s pps-tools package,
”…””}”(hjà  hžhhŸNh NubhÔ)”}”(hŒhttp://linuxpps.org”h]”hŒhttp://linuxpps.org”…””}”(hjè  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jê  uh1hÓhjà  ubhŒ , or ”…””}”(hjà  hžhhŸNh NubhÔ)”}”(hŒ%https://github.com/redlab-i/pps-tools”h]”hŒ%https://github.com/redlab-i/pps-tools”…””}”(hjû  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”jý  uh1hÓhjà  ubhŒ.”…””}”(hjà  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K®hjÏ  hžhubhÊ)”}”(hŒcOnce you have enabled the compilation of pps-ktimer just modprobe it (if
not statically compiled)::”h]”hŒbOnce you have enabled the compilation of pps-ktimer just modprobe it (if
not statically compiled):”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K³hjÏ  hžhubj8  )”}”(hŒ# modprobe pps-ktimer”h]”hŒ# modprobe pps-ktimer”…””}”hj"  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h K¶hjÏ  hžhubhÊ)”}”(hŒand the run ppstest as follow::”h]”hŒand the run ppstest as follow:”…””}”(hj0  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K¸hjÏ  hžhubj8  )”}”(hXŠ  $ ./ppstest /dev/pps1
trying PPS source "/dev/pps1"
found PPS source "/dev/pps1"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1186592699.388832443, sequence: 364 - clear  0.000000000, sequence: 0
source 0 - assert 1186592700.388931295, sequence: 365 - clear  0.000000000, sequence: 0
source 0 - assert 1186592701.389032765, sequence: 366 - clear  0.000000000, sequence: 0”h]”hXŠ  $ ./ppstest /dev/pps1
trying PPS source "/dev/pps1"
found PPS source "/dev/pps1"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1186592699.388832443, sequence: 364 - clear  0.000000000, sequence: 0
source 0 - assert 1186592700.388931295, sequence: 365 - clear  0.000000000, sequence: 0
source 0 - assert 1186592701.389032765, sequence: 366 - clear  0.000000000, sequence: 0”…””}”hj>  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h KºhjÏ  hžhubhÊ)”}”(hŒŠPlease note that to compile userland programs, you need the file timepps.h.
This is available in the pps-tools repository mentioned above.”h]”hŒŠPlease note that to compile userland programs, you need the file timepps.h.
This is available in the pps-tools repository mentioned above.”…””}”(hjL  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KÂhjÏ  hžhubeh}”(h]”Œtesting-the-pps-support”ah ]”h"]”Œtesting the pps support”ah$]”h&]”uh1h´hh¶hžhhŸh³h K¬ubhµ)”}”(hhh]”(hº)”}”(hŒ
Generators”h]”hŒ
Generators”…””}”(hje  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjb  hžhhŸh³h KÇubhÊ)”}”(hŒÆSometimes one needs to be able not only to catch PPS signals but to produce
them also. For example, running a distributed simulation, which requires
computers' clock to be synchronized very tightly.”h]”hŒÈSometimes one needs to be able not only to catch PPS signals but to produce
them also. For example, running a distributed simulation, which requires
computersâ€™ clock to be synchronized very tightly.”…””}”(hjs  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KÉhjb  hžhubhÊ)”}”(hŒTo do so the class pps-gen has been added. PPS generators can be
registered in the kernel by defining a struct pps_gen_source_info as
follows::”h]”hŒŽTo do so the class pps-gen has been added. PPS generators can be
registered in the kernel by defining a struct pps_gen_source_info as
follows:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KÍhjb  hžhubj8  )”}”(hŒÛstatic const struct pps_gen_source_info pps_gen_dummy_info = {
        .use_system_clock       = true,
        .get_time               = pps_gen_dummy_get_time,
        .enable                 = pps_gen_dummy_enable,
};”h]”hŒÛstatic const struct pps_gen_source_info pps_gen_dummy_info = {
        .use_system_clock       = true,
        .get_time               = pps_gen_dummy_get_time,
        .enable                 = pps_gen_dummy_enable,
};”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h KÑhjb  hžhubhÊ)”}”(hX*  Where the use_system_clock states if the generator uses the system
clock to generate its pulses, or they are from a peripheral device
clock. Method get_time() is used to query the time stored into the
generator clock, while the method enable() is used to enable or
disable the PPS pulse generation.”h]”hX*  Where the use_system_clock states if the generator uses the system
clock to generate its pulses, or they are from a peripheral device
clock. Method get_time() is used to query the time stored into the
generator clock, while the method enable() is used to enable or
disable the PPS pulse generation.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h K×hjb  hžhubhÊ)”}”(hŒ…Then calling the function pps_gen_register_source() in your
initialization routine as follows creates a new generator in the
system::”h]”hŒ„Then calling the function pps_gen_register_source() in your
initialization routine as follows creates a new generator in the
system:”…””}”(hj«  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KÝhjb  hžhubj8  )”}”(hŒ7pps_gen = pps_gen_register_source(&pps_gen_dummy_info);”h]”hŒ7pps_gen = pps_gen_register_source(&pps_gen_dummy_info);”…””}”hj¹  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h Káhjb  hžhubeh}”(h]”Œ
generators”ah ]”h"]”Œ
generators”ah$]”h&]”uh1h´hh¶hžhhŸh³h KÇubhµ)”}”(hhh]”(hº)”}”(hŒGenerators SYSFS support”h]”hŒGenerators SYSFS support”…””}”(hjÒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hjÏ  hžhhŸh³h KäubhÊ)”}”(hŒJIf the SYSFS filesystem is enabled in the kernel it provides a new class::”h]”hŒIIf the SYSFS filesystem is enabled in the kernel it provides a new class:”…””}”(hjà  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KæhjÏ  hžhubj8  )”}”(hŒ8$ ls /sys/class/pps-gen/
pps-gen0/  pps-gen1/  pps-gen2/”h]”hŒ8$ ls /sys/class/pps-gen/
pps-gen0/  pps-gen1/  pps-gen2/”…””}”hjî  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h KèhjÏ  hžhubhÊ)”}”(hŒlEvery directory is the ID of a PPS generator defined in the system and
inside of it you find several files::”h]”hŒkEvery directory is the ID of a PPS generator defined in the system and
inside of it you find several files:”…””}”(hjü  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KëhjÏ  hžhubj8  )”}”(hŒ`$ ls -F /sys/class/pps-gen/pps-gen0/
dev  enable  name  power/  subsystem@  system  time  uevent”h]”hŒ`$ ls -F /sys/class/pps-gen/pps-gen0/
dev  enable  name  power/  subsystem@  system  time  uevent”…””}”hj
  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h KîhjÏ  hžhubhÊ)”}”(hŒCTo enable the PPS signal generation you can use the command below::”h]”hŒBTo enable the PPS signal generation you can use the command below:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h KñhjÏ  hžhubj8  )”}”(hŒ-$ echo 1 > /sys/class/pps-gen/pps-gen0/enable”h]”hŒ-$ echo 1 > /sys/class/pps-gen/pps-gen0/enable”…””}”hj&  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h KóhjÏ  hžhubeh}”(h]”Œgenerators-sysfs-support”ah ]”h"]”Œgenerators sysfs support”ah$]”h&]”uh1h´hh¶hžhhŸh³h Käubhµ)”}”(hhh]”(hº)”}”(hŒParallel port generator”h]”hŒParallel port generator”…””}”(hj?  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj<  hžhhŸh³h KöubhÊ)”}”(hX2  One way to do this is to invent some complicated hardware solutions but it
may be neither necessary nor affordable. The cheap way is to load a PPS
generator on one of the computers (master) and PPS clients on others
(slaves), and use very simple cables to deliver signals using parallel
ports, for example.”h]”hX2  One way to do this is to invent some complicated hardware solutions but it
may be neither necessary nor affordable. The cheap way is to load a PPS
generator on one of the computers (master) and PPS clients on others
(slaves), and use very simple cables to deliver signals using parallel
ports, for example.”…””}”(hjM  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Køhj<  hžhubhÊ)”}”(hŒParallel port cable pinout::”h]”hŒParallel port cable pinout:”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Kþhj<  hžhubj8  )”}”(hXa  pin     name    master      slave
1       STROBE    *------     *
2       D0        *     |     *
3       D1        *     |     *
4       D2        *     |     *
5       D3        *     |     *
6       D4        *     |     *
7       D5        *     |     *
8       D6        *     |     *
9       D7        *     |     *
10      ACK       *     ------*
11      BUSY      *           *
12      PE        *           *
13      SEL       *           *
14      AUTOFD    *           *
15      ERROR     *           *
16      INIT      *           *
17      SELIN     *           *
18-25   GND       *-----------*”h]”hXa  pin     name    master      slave
1       STROBE    *------     *
2       D0        *     |     *
3       D1        *     |     *
4       D2        *     |     *
5       D3        *     |     *
6       D4        *     |     *
7       D5        *     |     *
8       D6        *     |     *
9       D7        *     |     *
10      ACK       *     ------*
11      BUSY      *           *
12      PE        *           *
13      SEL       *           *
14      AUTOFD    *           *
15      ERROR     *           *
16      INIT      *           *
17      SELIN     *           *
18-25   GND       *-----------*”…””}”hji  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h M hj<  hžhubhÊ)”}”(hX´  Please note that parallel port interrupt occurs only on high->low transition,
so it is used for PPS assert edge. PPS clear edge can be determined only
using polling in the interrupt handler which actually can be done way more
precisely because interrupt handling delays can be quite big and random. So
current parport PPS generator implementation (pps_gen_parport module) is
geared towards using the clear edge for time synchronization.”h]”hX´  Please note that parallel port interrupt occurs only on high->low transition,
so it is used for PPS assert edge. PPS clear edge can be determined only
using polling in the interrupt handler which actually can be done way more
precisely because interrupt handling delays can be quite big and random. So
current parport PPS generator implementation (pps_gen_parport module) is
geared towards using the clear edge for time synchronization.”…””}”(hjw  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Mhj<  hžhubhÊ)”}”(hXv  Clear edge polling is done with disabled interrupts so it's better to select
delay between assert and clear edge as small as possible to reduce system
latencies. But if it is too small slave won't be able to capture clear edge
transition. The default of 30us should be good enough in most situations.
The delay can be selected using 'delay' pps_gen_parport module parameter.”h]”hX~  Clear edge polling is done with disabled interrupts so itâ€™s better to select
delay between assert and clear edge as small as possible to reduce system
latencies. But if it is too small slave wonâ€™t be able to capture clear edge
transition. The default of 30us should be good enough in most situations.
The delay can be selected using â€˜delayâ€™ pps_gen_parport module parameter.”…””}”(hj…  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h Mhj<  hžhubeh}”(h]”Œparallel-port-generator”ah ]”h"]”Œparallel port generator”ah$]”h&]”uh1h´hh¶hžhhŸh³h Köubhµ)”}”(hhh]”(hº)”}”(hŒ$Intel Timed I/O PPS signal generator”h]”hŒ$Intel Timed I/O PPS signal generator”…””}”(hjž  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hj›  hžhhŸh³h M#ubhÊ)”}”(hŒpIntel Timed I/O is a high precision device, present on 2019 and newer Intel
CPUs, that can generate PPS signals.”h]”hŒpIntel Timed I/O is a high precision device, present on 2019 and newer Intel
CPUs, that can generate PPS signals.”…””}”(hj¬  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h M%hj›  hžhubhÊ)”}”(hXŸ  Timed I/O and system time are both driven by same hardware clock. The signal
is generated with a precision of ~20 nanoseconds. The generated PPS signal
is used to synchronize an external device with system clock. For example,
it can be used to share your clock with a device that receives PPS signal,
generated by Timed I/O device. There are dedicated Timed I/O pins to deliver
the PPS signal to an external device.”h]”hXŸ  Timed I/O and system time are both driven by same hardware clock. The signal
is generated with a precision of ~20 nanoseconds. The generated PPS signal
is used to synchronize an external device with system clock. For example,
it can be used to share your clock with a device that receives PPS signal,
generated by Timed I/O device. There are dedicated Timed I/O pins to deliver
the PPS signal to an external device.”…””}”(hjº  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h M(hj›  hžhubhÊ)”}”(hŒ*Usage of Intel Timed I/O as PPS generator:”h]”hŒ*Usage of Intel Timed I/O as PPS generator:”…””}”(hjÈ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h M/hj›  hžhubhÊ)”}”(hŒStart generating PPS signal::”h]”hŒStart generating PPS signal:”…””}”(hjÖ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h M1hj›  hžhubj8  )”}”(hŒ,$echo 1 > /sys/class/pps-gen/pps-genx/enable”h]”hŒ,$echo 1 > /sys/class/pps-gen/pps-genx/enable”…””}”hjä  sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h M3hj›  hžhubhÊ)”}”(hŒStop generating PPS signal::”h]”hŒStop generating PPS signal:”…””}”(hjò  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÉhŸh³h M5hj›  hžhubj8  )”}”(hŒ,$echo 0 > /sys/class/pps-gen/pps-genx/enable”h]”hŒ,$echo 0 > /sys/class/pps-gen/pps-genx/enable”…””}”hj   sbah}”(h]”h ]”h"]”h$]”h&]”h±h²uh1j7  hŸh³h M7hj›  hžhubeh}”(h]”Œ$intel-timed-i-o-pps-signal-generator”ah ]”h"]”Œ$intel timed i/o pps signal generator”ah$]”h&]”uh1h´hh¶hžhhŸh³h M#ubeh}”(h]”Œpps-pulse-per-second”ah ]”h"]”Œpps - pulse per second”ah$]”h&]”uh1h´hhhžhhŸh³h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h³uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¹NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”jA  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h³Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j  j  jY  jV  jÒ  jÏ  j  j  jØ  jÕ  jÌ  jÉ  j_  j\  jÌ  jÉ  j9  j6  j˜  j•  j  j  uŒ	nametypes”}”(j  ‰jY  ‰jÒ  ‰j  ‰jØ  ‰jÌ  ‰j_  ‰jÌ  ‰j9  ‰j˜  ‰j  ‰uh}”(j  h¶jV  j  jÏ  j\  j  jÕ  jÕ  j  jÉ  jÛ  j\  jÏ  jÉ  jb  j6  jÏ  j•  j<  j  j›  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
decoration”Nhžhub.