diff options
Diffstat (limited to 'Documentation/pps/pps.txt')
| -rw-r--r-- | Documentation/pps/pps.txt | 44 |
1 files changed, 23 insertions, 21 deletions
diff --git a/Documentation/pps/pps.txt b/Documentation/pps/pps.txt index 1fdbd5447216..99f5d8c4c652 100644 --- a/Documentation/pps/pps.txt +++ b/Documentation/pps/pps.txt @@ -48,12 +48,12 @@ problem: time_pps_create(). This implies that the source has a /dev/... entry. This assumption is -ok for the serial and parallel port, where you can do something +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 +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. +precondition for the use of a PPS API. The problem can be simply solved if you consider that a PPS source is not always connected with a GPS data source. @@ -88,13 +88,13 @@ Coding example -------------- To register a PPS source into the kernel you should define a struct -pps_source_info_s as follows: +pps_source_info as follows: static struct pps_source_info pps_ktimer_info = { .name = "ktimer", .path = "", - .mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | \ - PPS_ECHOASSERT | \ + .mode = PPS_CAPTUREASSERT | PPS_OFFSETASSERT | + PPS_ECHOASSERT | PPS_CANWAIT | PPS_TSFMT_TSPEC, .echo = pps_ktimer_echo, .owner = THIS_MODULE, @@ -108,13 +108,13 @@ initialization routine as follows: The pps_register_source() prototype is: - int pps_register_source(struct pps_source_info_s *info, int default_params) + int pps_register_source(struct pps_source_info *info, int default_params) 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_s which describe the capabilities of the driver). +pps_source_info which describe the capabilities of the driver). Once you have registered a new PPS source into the system you can signal an assert event (for example in the interrupt handler routine) @@ -142,8 +142,10 @@ If the SYSFS filesystem is enabled in the kernel it provides a new class: Every directory is the ID of a PPS sources defined in the system and inside you find several files: - $ ls /sys/class/pps/pps0/ - assert clear echo mode name path subsystem@ uevent + $ ls -F /sys/class/pps/pps0/ + assert dev mode path subsystem@ + clear echo name power/ uevent + Inside each "assert" and "clear" file you can find the timestamp and a sequence number: @@ -154,32 +156,32 @@ sequence number: Where before the "#" is the timestamp in seconds; after it is the sequence number. Other files are: -* echo: reports if the PPS source has an echo function or not; + * echo: reports if the PPS source has an echo function or not; -* mode: reports available PPS functioning modes; + * mode: reports available PPS functioning modes; -* name: reports the PPS source's name; + * 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). + * path: reports the PPS source's device path, that is the device the + PPS source is connected to (if it exists). Testing the PPS support ----------------------- In order to test the PPS support even without specific hardware you can use -the ktimer driver (see the client subsection in the PPS configuration menu) +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/ago/pps-tools . +http://linuxpps.org , or https://github.com/redlab-i/pps-tools. -Once you have enabled the compilation of ktimer just modprobe it (if +Once you have enabled the compilation of pps-ktimer just modprobe it (if not statically compiled): - # modprobe ktimer + # modprobe pps-ktimer and the run ppstest as follow: - $ ./ppstest /dev/pps0 + $ ./ppstest /dev/pps1 trying PPS source "/dev/pps1" found PPS source "/dev/pps1" ok, found 1 source(s), now start fetching data... @@ -187,7 +189,7 @@ and the run ppstest as follow: source 0 - assert 1186592700.388931295, sequence: 365 - clear 0.000000000, sequence: 0 source 0 - assert 1186592701.389032765, sequence: 366 - clear 0.000000000, sequence: 0 -Please, note that to compile userland programs you need the file timepps.h . +Please note that to compile userland programs, you need the file timepps.h. This is available in the pps-tools repository mentioned above. |