Documentation/driver-api/pps.rst

4 PPS - Pulse Per Second
25 system several PPS sources.
27 PPS means "pulse per second" and a PPS source is just a device which
31 A PPS source can be connected to a serial port (usually to the Data
38 GPS receiver as PPS source, to obtain a wallclock-time with
45 While implementing a PPS API as RFC 2783 defines and using an embedded
55 task for a PPS API. But this assumption does not work for a single
58 precondition for the use of a PPS API.
60 The problem can be simply solved if you consider that a PPS source is
64 for instance) is a PPS source too, and if not they should provide the
65 possibility to open another device as PPS source.
67 In LinuxPPS the PPS sources are simply char devices usually mapped
71 PPS with USB to serial devices
74 It is possible to grab the PPS from an USB to serial device. However,
77 synchronized with PPS through USB. With USB 2.0, jitter may decrease
83 If your device doesn't report PPS, you can check that the feature is
92 To register a PPS source into the kernel you should define a struct
116 PPS source, "default_params" tells the system what the initial default
121 Once you have registered a new PPS source into the system you can
144 Every directory is the ID of a PPS sources defined in the system and
161  * echo: reports if the PPS source has an echo function or not;
163  * mode: reports available PPS functioning modes;
165  * name: reports the PPS source's name;
167  * path: reports the PPS source's device path, that is the device the
168    PPS source is connected to (if it exists).
171 Testing the PPS support
174 In order to test the PPS support even without specific hardware you can use
175 the pps-ktimer driver (see the client subsection in the PPS configuration menu)
187    trying PPS source "/dev/pps1"
188    found PPS source "/dev/pps1"
201 Sometimes one needs to be able not only to catch PPS signals but to produce
205 nor affordable. The cheap way is to load a PPS generator on one of the
206 computers (master) and PPS clients on others (slaves), and use very simple
232 so it is used for PPS assert edge. PPS clear edge can be determined only
235 current parport PPS generator implementation (pps_gen_parport module) is