Devuan fork of gpsd
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  1. <?xml version="1.0" encoding="ISO-8859-1"?>
  2. <!--
  3. This file is Copyright (c) 2016 by the GPSD project
  4. SPDX-License-Identifier: BSD-2-clause
  5. -->
  6. <!DOCTYPE refentry PUBLIC
  7. "-//OASIS//DTD DocBook XML V4.1.2//EN"
  8. "">
  9. <refentry id='ppscheck.8'>
  10. <refentryinfo><date>28 Jul 2016</date></refentryinfo>
  11. <refmeta>
  12. <refentrytitle>ppscheck</refentrytitle>
  13. <manvolnum>8</manvolnum>
  14. <refmiscinfo class="source">The GPSD Project</refmiscinfo>
  15. <refmiscinfo class="manual">GPSD Documentation</refmiscinfo>
  16. </refmeta>
  17. <refnamediv id='name'>
  18. <refname>ppscheck</refname>
  19. <refpurpose>tool to check a serial port for PPS</refpurpose>
  20. </refnamediv>
  21. <refsynopsisdiv id='synopsis'>
  22. <cmdsynopsis>
  23. <command>ppscheck</command>
  24. <arg choice='opt'>-h </arg>
  25. <arg choice='opt'>-V </arg>
  26. <arg choice='plain'><replaceable>device</replaceable></arg>
  27. </cmdsynopsis>
  28. </refsynopsisdiv>
  29. <refsect1 id='description'><title>DESCRIPTION</title>
  30. <para>ppscheck watches a specified serial port for transitions that
  31. might be PPS. It looks for changes in handshake lines CD, RI, and CTS
  32. by running ioctl(...., TIOCMIWAIT, ...) in a loop. When it sees a state
  33. change it emits a timestamped line of output dumping the state of the
  34. handshake signals. It's useful for checking whether a device is emitting
  35. PPS.</para>
  36. <para>To check the first serial port do this:</para>
  37. <programlisting>
  38. ppscheck /dev/ttyS0
  39. </programlisting>
  40. <para>ppscheck is not intended for routine use, but rather for
  41. diagnostic purposes. Once you have verified a particular device can
  42. output PPS signals you will never need to use it again on that device.
  43. </para>
  44. <para>The program accepts the following options:</para>
  45. <variablelist remap='TP'>
  46. <varlistentry>
  47. <term>-h</term>
  48. <listitem><para>Display help message and terminate.</para></listitem>
  49. </varlistentry>
  50. <varlistentry>
  51. <term>-V</term>
  52. <listitem>
  53. <para>Dump version and exit.</para>
  54. </listitem>
  55. </varlistentry>
  56. </variablelist>
  57. <para>The "device" argument should be the pathname of a device. It will
  58. be the device monitored. </para>
  59. <para>Each output line is the second and nanosecond parts of a timestamp
  60. followed by the names of the handshake signals then asserted. Off
  61. transitions may generate lines with no signals aserted. </para>
  62. <para>If you don't see output within a second, use gpsmon or some other
  63. equivalent tool to check that your device has a satellite lock and is
  64. getting 3D fixes before giving up on the possibility of PPS. </para>
  65. <para>Check your cable. Cheap DB9 to DB9 cables such as those issued
  66. with UPSes often carry TXD/RXD/GND only, omitting handshake lines such
  67. as DCD. Suspect this especially if the cable jacket looks too skinny to
  68. hold more than three leads! </para>
  69. <para>Most GPS that have built in USB do not support PPS. When in doubt,
  70. contact the vendor for confirmation that your device does supply PPS.
  71. </para>
  72. </refsect1>
  73. <refsect1 id='exit_status'><title>RETURN VALUES</title>
  74. <para>1 if the device counld not be opened. 0 otherwise</para>
  75. </refsect1>
  76. <refsect1 id='see_also'><title>SEE ALSO</title>
  77. <para>
  78. <citerefentry><refentrytitle>gpsd</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  79. </para>
  80. </refsect1>
  81. <refsect1 id='maintainer'><title>AUTHOR</title>
  82. <para>Eric S. Raymond <email></email>.</para>
  83. </refsect1>
  84. </refentry>