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diff --git a/doc/telemetry.xsl b/doc/telemetry.xsl new file mode 100644 index 00000000..fa66bff9 --- /dev/null +++ b/doc/telemetry.xsl @@ -0,0 +1,806 @@ +<?xml version="1.0" encoding="utf-8" ?> +<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" +"/usr/share/xml/docbook/schema/dtd/4.5/docbookx.dtd"> + +<article> + <articleinfo> + <title>AltOS Telemetry</title> + <subtitle>Packet Definitions</subtitle> + <author> + <firstname>Keith</firstname> + <surname>Packard</surname> + </author> + <copyright> + <year>2011</year> + <holder>Keith Packard</holder> + </copyright> + <legalnotice> + <para> + This document is released under the terms of the + <ulink url="http://creativecommons.org/licenses/by-sa/3.0/"> + Creative Commons ShareAlike 3.0 + </ulink> + license. + </para> + </legalnotice> + <revhistory> + <revision> + <revnumber>0.1</revnumber> + <date>01 July 2011</date> + <revremark>Initial content</revremark> + </revision> + </revhistory> + </articleinfo> + <section> + <title>Packet Format Design</title> + <para> + AltOS telemetry data is split into multiple different packets, + all the same size, but each includs an identifier so that the + ground station can distinguish among different types. A single + flight board will transmit multiple packet types, each type on a + different schedule. The ground software need look for only a + single packet size, and then decode the information within the + packet and merge data from multiple packets to construct the + full flight computer state. + </para> + <para> + Each AltOS packet is 32 bytes long. This size was chosen based + on the known telemetry data requirements. The power of two size + allows them to be stored easily in flash memory without having + them split across blocks or leaving gaps at the end. + </para> + <para> + All packet types start with a five byte header which encodes the + device serial number, device clock value and the packet + type. The remaining 27 bytes encode type-specific data. + </para> + </section> + <section> + <title>Packet Formats</title> + This section first defines the packet header common to all packets + and then the per-packet data layout. + <section> + <title>Packet Header</title> + <table frame='all'> + <title>Telemetry Packet Header</title> + <tgroup cols='4' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='center' colwidth='3*' colname='Data Type'/> + <colspec align='left' colwidth='3*' colname='Name'/> + <colspec align='left' colwidth='9*' colname='Description'/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Data Type</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0</entry> + <entry>uint16_t</entry> + <entry>serial</entry> + <entry>Device serial Number</entry> + </row> + <row> + <entry>2</entry> + <entry>uint16_t</entry> + <entry>tick</entry> + <entry>Device time in 100ths of a second</entry> + </row> + <row> + <entry>4</entry> + <entry>uint8_t</entry> + <entry>type</entry> + <entry>Packet type</entry> + </row> + <row> + <entry>5</entry> + </row> + </tbody> + </tgroup> + </table> + <para> + Each packet starts with these five bytes which serve to identify + which device has transmitted the packet, when it was transmitted + and what the rest of the packet contains. + </para> + </section> + <section> + <title>Sensor Data</title> + <informaltable frame='none' label='' tocentry='0'> + <tgroup cols='2' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='left' colwidth='3*' colname='Description'/> + <thead> + <row> + <entry>Type</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0x01</entry> + <entry>TeleMetrum Sensor Data</entry> + </row> + <row> + <entry>0x02</entry> + <entry>TeleMini Sensor Data</entry> + </row> + <row> + <entry>0x03</entry> + <entry>TeleNano Sensor Data</entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + TeleMetrum, TeleMini and TeleNano share this same packet + format for sensor data. Each uses a distinct packet type so + that the receiver knows which data values are valid and which + are undefined. + </para> + <para> + Sensor Data packets are transmitted once per second on the + ground, 10 times per second during ascent and once per second + during descent and landing + </para> + <table frame='all'> + <title>Sensor Packet Contents</title> + <tgroup cols='4' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='center' colwidth='3*' colname='Data Type'/> + <colspec align='left' colwidth='3*' colname='Name'/> + <colspec align='left' colwidth='9*' colname='Description'/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Data Type</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>5</entry><entry>uint8_t</entry><entry>state</entry><entry>Flight state</entry> + </row> + <row> + <entry>6</entry><entry>int16_t</entry><entry>accel</entry><entry>accelerometer (TM only)</entry> + </row> + <row> + <entry>8</entry><entry>int16_t</entry><entry>pres</entry><entry>pressure sensor</entry> + </row> + <row> + <entry>10</entry><entry>int16_t</entry><entry>temp</entry><entry>temperature sensor</entry> + </row> + <row> + <entry>12</entry><entry>int16_t</entry><entry>v_batt</entry><entry>battery voltage</entry> + </row> + <row> + <entry>14</entry><entry>int16_t</entry><entry>sense_d</entry><entry>drogue continuity sense (TM/Tm)</entry> + </row> + <row> + <entry>16</entry><entry>int16_t</entry><entry>sense_m</entry><entry>main continuity sense (TM/Tm)</entry> + </row> + <row> + <entry>18</entry><entry>int16_t</entry><entry>acceleration</entry><entry>m/s² * 16</entry> + </row> + <row> + <entry>20</entry><entry>int16_t</entry><entry>speed</entry><entry>m/s * 16</entry> + </row> + <row> + <entry>22</entry><entry>int16_t</entry><entry>height</entry><entry>m</entry> + </row> + <row> + <entry>24</entry><entry>int16_t</entry><entry>ground_pres</entry><entry>Average barometer reading on ground</entry> + </row> + <row> + <entry>26</entry><entry>int16_t</entry><entry>ground_accel</entry><entry>TM</entry> + </row> + <row> + <entry>28</entry><entry>int16_t</entry><entry>accel_plus_g</entry><entry>TM</entry> + </row> + <row> + <entry>30</entry><entry>int16_t</entry><entry>accel_minus_g</entry><entry>TM</entry> + </row> + <row> + <entry>32</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section> + <title>Configuration Data</title> + <informaltable frame='none' label='' tocentry='0'> + <tgroup cols='2' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='left' colwidth='3*' colname='Description'/> + <thead> + <row> + <entry>Type</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0x04</entry> + <entry>Configuration Data</entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + This provides a description of the software installed on the + flight computer as well as any user-specified configuration data. + </para> + <para> + Configuration data packets are transmitted once per second + during all phases of the flight + </para> + <table frame='all'> + <title>Sensor Packet Contents</title> + <tgroup cols='4' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='center' colwidth='3*' colname='Data Type'/> + <colspec align='left' colwidth='3*' colname='Name'/> + <colspec align='left' colwidth='9*' colname='Description'/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Data Type</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>5</entry><entry>uint8_t</entry><entry>type</entry><entry>Device type</entry> + </row> + <row> + <entry>6</entry><entry>uint16_t</entry><entry>flight</entry><entry>Flight number</entry> + </row> + <row> + <entry>8</entry><entry>uint8_t</entry><entry>config_major</entry><entry>Config major version</entry> + </row> + <row> + <entry>9</entry><entry>uint8_t</entry><entry>config_minor</entry><entry>Config minor version</entry> + </row> + <row> + <entry>10</entry><entry>uint16_t</entry><entry>apogee_delay</entry> + <entry>Apogee deploy delay in seconds</entry> + </row> + <row> + <entry>12</entry><entry>uint16_t</entry><entry>main_deploy</entry><entry>Main deploy alt in meters</entry> + </row> + <row> + <entry>14</entry><entry>uint16_t</entry><entry>flight_log_max</entry> + <entry>Maximum flight log size (kB)</entry> + </row> + <row> + <entry>16</entry><entry>char</entry><entry>callsign[8]</entry><entry>Radio operator identifier</entry> + </row> + <row> + <entry>24</entry><entry>char</entry><entry>version[8]</entry><entry>Software version identifier</entry> + </row> + <row> + <entry>32</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section> + <title>GPS Location</title> + <informaltable frame='none' label='' tocentry='0'> + <tgroup cols='2' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='left' colwidth='3*' colname='Description'/> + <thead> + <row> + <entry>Type</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0x05</entry> + <entry>GPS Location</entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + This packet provides all of the information available from the + Venus SkyTraq GPS receiver—position, time, speed and precision + estimates. + </para> + <para> + GPS Location packets are transmitted once per second during + all phases of the flight + </para> + <table frame='all'> + <title>GPS Location Packet Contents</title> + <tgroup cols='4' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='center' colwidth='3*' colname='Data Type'/> + <colspec align='left' colwidth='3*' colname='Name'/> + <colspec align='left' colwidth='9*' colname='Description'/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Data Type</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>5</entry><entry>uint8_t</entry><entry>flags</entry> + <entry>See GPS Flags table below</entry> + </row> + <row> + <entry>6</entry><entry>int16_t</entry><entry>altitude</entry><entry>m</entry> + </row> + <row> + <entry>8</entry><entry>int32_t</entry><entry>latitude</entry><entry>degrees * 10<superscript>7</superscript></entry> + </row> + <row> + <entry>12</entry><entry>int32_t</entry><entry>longitude</entry><entry>degrees * 10<superscript>7</superscript></entry> + </row> + <row> + <entry>16</entry><entry>uint8_t</entry><entry>year</entry> + </row> + <row> + <entry>17</entry><entry>uint8_t</entry><entry>month</entry> + </row> + <row> + <entry>18</entry><entry>uint8_t</entry><entry>day</entry> + </row> + <row> + <entry>19</entry><entry>uint8_t</entry><entry>hour</entry> + </row> + <row> + <entry>20</entry><entry>uint8_t</entry><entry>minute</entry> + </row> + <row> + <entry>21</entry><entry>uint8_t</entry><entry>second</entry> + </row> + <row> + <entry>22</entry><entry>uint8_t</entry><entry>pdop</entry><entry>* 5</entry> + </row> + <row> + <entry>23</entry><entry>uint8_t</entry><entry>hdop</entry><entry>* 5</entry> + </row> + <row> + <entry>24</entry><entry>uint8_t</entry><entry>vdop</entry><entry>* 5</entry> + </row> + <row> + <entry>25</entry><entry>uint8_t</entry><entry>mode</entry> + <entry>See GPS Mode table below</entry> + </row> + <row> + <entry>26</entry><entry>uint16_t</entry><entry>ground_speed</entry><entry>cm/s</entry> + </row> + <row> + <entry>28</entry><entry>int16_t</entry><entry>climb_rate</entry><entry>cm/s</entry> + </row> + <row> + <entry>30</entry><entry>uint8_t</entry><entry>course</entry><entry>/ 2</entry> + </row> + <row> + <entry>31</entry><entry>uint8_t</entry><entry>unused[1]</entry> + </row> + <row> + <entry>32</entry> + </row> + </tbody> + </tgroup> + </table> + <para> + Packed into a one byte field are status flags and the count of + satellites used to compute the position fix. Note that this + number may be lower than the number of satellites being + tracked; the receiver will not use information from satellites + with weak signals or which are close enough to the horizon to + have significantly degraded position accuracy. + </para> + <table frame='all'> + <title>GPS Flags</title> + <tgroup cols='3' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='bits'/> + <colspec align='left' colwidth='2*' colname='name'/> + <colspec align='left' colwidth='7*' colname='description'/> + <thead> + <row> + <entry align='center'>Bits</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0-3</entry> + <entry>nsats</entry> + <entry>Number of satellites in solution</entry> + </row> + <row> + <entry>4</entry> + <entry>valid</entry> + <entry>GPS solution is valid</entry> + </row> + <row> + <entry>5</entry> + <entry>running</entry> + <entry>GPS receiver is operational</entry> + </row> + <row> + <entry>6</entry> + <entry>date_valid</entry> + <entry>Reported date is valid</entry> + </row> + <row> + <entry>7</entry> + <entry>course_valid</entry> + <entry>ground speed, course and climb rates are valid</entry> + </row> + </tbody> + </tgroup> + </table> + <para> + Here are all of the valid GPS operational modes. Altus Metrum + products will only ever report 'N' (not valid), 'A' + (Autonomous) modes or 'E' (Estimated). The remaining modes + are either testing modes or require additional data. + </para> + <table frame='all'> + <title>GPS Mode</title> + <tgroup cols='3' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='value'/> + <colspec align='center' colwidth='3*' colname='name'/> + <colspec align='left' colwidth='7*' colname='description'/> + <thead> + <row> + <entry align='center'>Mode</entry> + <entry align='center'>Name</entry> + <entry align='center'>Decsription</entry> + </row> + </thead> + <tbody> + <row> + <entry>N</entry> + <entry>Not Valid</entry> + <entry>All data are invalid</entry> + </row> + <row> + <entry>A</entry> + <entry>Autonomous mode</entry> + <entry>Data are derived from satellite data</entry> + </row> + <row> + <entry>D</entry> + <entry>Differential Mode</entry> + <entry> + Data are augmented with differential data from a + known ground station. The SkyTraq unit in TeleMetrum + does not support this mode + </entry> + </row> + <row> + <entry>E</entry> + <entry>Estimated</entry> + <entry> + Data are estimated using dead reckoning from the + last known data + </entry> + </row> + <row> + <entry>M</entry> + <entry>Manual</entry> + <entry>Data were entered manually</entry> + </row> + <row> + <entry>S</entry> + <entry>Simulated</entry> + <entry>GPS receiver testing mode</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section> + <title>GPS Satellite Data</title> + <informaltable frame='none' label='' tocentry='0'> + <tgroup cols='2' align='center' colsep='1' rowsep='1'> + <colspec align='center' colwidth='*' colname='Offset'/> + <colspec align='left' colwidth='3*' colname='Description'/> + <thead> + <row> + <entry>Type</entry> + <entry>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0x06</entry> + <entry>GPS Satellite Data</entry> + </row> + </tbody> + </tgroup> + </informaltable> + <para> + This packet provides space vehicle identifiers and signal + quality information in the form of a C/N1 number for up to 12 + satellites. The order of the svids is not specified. + </para> + <para> + GPS Satellite data are transmitted once per second during all + phases of the flight. + </para> + <table frame='all'> + <title>GPS Satellite Data Contents</title> + <tgroup cols='4' align='center' colsep='1' rowsep='1'> + <colspec align='right' colwidth='*' colname='Offset'/> + <colspec align='center' colwidth='3*' colname='Data Type'/> + <colspec align='left' colwidth='3*' colname='Name'/> + <colspec align='left' colwidth='9*' colname='Description'/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Data Type</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>5</entry><entry>uint8_t</entry><entry>channels</entry> + <entry>Number of reported satellite information</entry> + </row> + <row> + <entry>6</entry><entry>sat_info_t</entry><entry>sats[12]</entry> + <entry>See Per-Satellite data table below</entry> + </row> + <row> + <entry>30</entry><entry>uint8_t</entry><entry>unused[2]</entry> + </row> + <row> + <entry>32</entry> + </row> + </tbody> + </tgroup> + </table> + <table frame='all'> + <title>GPS Per-Satellite data (sat_info_t)</title> + <tgroup cols='4' align='center' colsep='1' rowsep='1'> + <colspec align='right' colwidth='*' colname='Offset'/> + <colspec align='center' colwidth='3*' colname='Data Type'/> + <colspec align='left' colwidth='3*' colname='Name'/> + <colspec align='left' colwidth='9*' colname='Description'/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Data Type</entry> + <entry align='center'>Name</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0</entry><entry>uint8_t</entry><entry>svid</entry> + <entry>Space Vehicle Identifier</entry> + </row> + <row> + <entry>1</entry><entry>uint8_t</entry><entry>c_n_1</entry> + <entry>C/N1 signal quality indicator</entry> + </row> + <row> + <entry>2</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + </section> + <section> + <title>Data Transmission</title> + <para> + Altus Metrum devices use the Texas Instruments CC1111 + microcontroller which includes an integrated sub-GHz digital + transceiver. This transceiver is used to both transmit and + receive the telemetry packets. This section discusses what + modulation scheme is used and how this device is configured. + </para> + <section> + <title>Modulation Scheme</title> + <para> + Texas Instruments provides a tool for computing modulation + parameters given a desired modulation format and basic bit + rate. For AltOS, the basic bit rate was specified as 38 kBaud, + resulting in the following signal parmeters: + </para> + <table> + <tgroup cols='3'> + <colspec align="center" colwidth="*" colname="parameter"/> + <colspec align="center" text-align="." colwidth="*" colname="value"/> + <colspec align="center" colwidth="*" colname="description"/> + <thead> + <row> + <entry align='center'>Parameter</entry> + <entry align='center'>Value</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>Modulation</entry> + <entry>GFSK</entry> + <entry>Gaussian Frequency Shift Keying</entry> + </row> + <row> + <entry>Deviation</entry> + <entry>20.507812 kHz</entry> + <entry>Frequency modulation</entry> + </row> + <row> + <entry>Data rate</entry> + <entry>38.360596 kBaud</entry> + <entry>Raw bit rate</entry> + </row> + <row> + <entry>RX Filter Bandwidth</entry> + <entry>93.75 kHz</entry> + <entry>Receiver Band pass filter bandwidth</entry> + </row> + <row> + <entry>IF Frequency</entry> + <entry>140.62 kHz</entry> + <entry>Receiver intermediate frequency</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section> + <para> + The cc1111 provides forward error correction in hardware, + which AltOS uses to improve reception of weak signals. The + overall effect of this is to halve the available bandwidth for + data from 38 kBaud to 19 kBaud. + </para> + <title>Error Correction</title> + <table> + <tgroup cols='3'> + <colspec align="center" colwidth="*" colname="parameter"/> + <colspec align="center" colwidth="*" colname="value"/> + <colspec align="center" colwidth="*" colname="description"/> + <thead> + <row> + <entry align='center'>Parameter</entry> + <entry align='center'>Value</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>Error Correction</entry> + <entry>Convolutional coding FEC</entry> + <entry>1/2 code, constraint length m=4</entry> + </row> + <row> + <entry>Interleaving</entry> + <entry>4 x 4</entry> + <entry>Reduce effect of noise burst</entry> + </row> + <row> + <entry>Data Whitening</entry> + <entry>XOR with 9-bit PNR</entry> + <entry>Rotate right with bit 8 = bit 0 xor bit 5, initial + value 111111111</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + </section> + <section> + <title>TeleDongle packet format</title> + <para> + TeleDongle does not do any interpretation of the packet data, + instead it is configured to receive packets of a specified + length (32 bytes in this case). For each received packet, + TeleDongle produces a single line of text. This line starts with + the string "TELEM " and is followed by a list of hexadecimal + encoded bytes. + </para> + <programlisting>TELEM 224f01080b05765e00701f1a1bbeb8d7b60b070605140c000600000000000000003fa988</programlisting> + <para> + The hexadecimal encoded string of bytes contains a length byte, + the packet data, two bytes added by the cc1111 radio receiver + hardware and finally a checksum so that the host software can + validate that the line was transmitted without any errors. + </para> + <table> + <tgroup cols='4'> + <colspec align="center" colwidth="2*" colname="offset"/> + <colspec align="center" colwidth="*" colname="name"/> + <colspec align="center" colwidth="*" colname="value"/> + <colspec align="center" colwidth="5*" colname="description"/> + <thead> + <row> + <entry align='center'>Offset</entry> + <entry align='center'>Name</entry> + <entry align='center'>Example</entry> + <entry align='center'>Description</entry> + </row> + </thead> + <tbody> + <row> + <entry>0</entry> + <entry>length</entry> + <entry>22</entry> + <entry>Total length of data bytes in the line. Note that + this includes the added RSSI and status bytes</entry> + </row> + <row> + <entry>1 ·· length-3</entry> + <entry>packet</entry> + <entry>4f ·· 00</entry> + <entry>Bytes of actual packet data</entry> + </row> + <row> + <entry>length-2</entry> + <entry>rssi</entry> + <entry>3f</entry> + <entry>Received signal strength. dBm = rssi / 2 - 74</entry> + </row> + <row> + <entry>length-1</entry> + <entry>lqi</entry> + <entry>a9</entry> + <entry>Link Quality Indicator and CRC status. Bit 7 + is set when the CRC is correct</entry> + </row> + <row> + <entry>length</entry> + <entry>checksum</entry> + <entry>88</entry> + <entry>(0x5a + sum(bytes 1 ·· length-1)) % 256</entry> + </row> + </tbody> + </tgroup> + </table> + </section> + <section> + <title>History and Motivation</title> + <para> + The original AltoOS telemetry mechanism encoded everything + available piece of information on the TeleMetrum hardware into a + single unified packet. Initially, the packets contained very + little data—some raw sensor readings along with the current GPS + coordinates when a GPS receiver was connected. Over time, the + amount of data grew to include sensor calibration data, GPS + satellite information and a host of internal state information + designed to help diagnose flight failures in case of a loss of + the on-board flight data. + </para> + <para> + Because every packet contained all of the data, packets were + huge—95 bytes long. Much of the information was also specific to + the TeleMetrum hardware. With the introduction of the TeleMini + flight computer, most of the data contained in the telemetry + packets was unavailable. Initially, a shorter, but still + comprehensive packet was implemented. This required that the + ground station be pre-configured as to which kind of packet to + expect. + </para> + <para> + The development of several companion boards also made the + shortcomings evident—each companion board would want to include + telemetry data in the radio link; with the original design, the + packet would have to hold the new data as well, requiring + additional TeleMetrum and ground station changes. + </para> + </section> +</article> |