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diff --git a/doc/telemetry.xsl b/doc/telemetry.xsl index 8f0c3ff0..d2b17126 100644 --- a/doc/telemetry.xsl +++ b/doc/telemetry.xsl @@ -32,37 +32,6 @@ </revhistory> </articleinfo> <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> - <section> <title>Packet Format Design</title> <para> AltOS telemetry data is split into multiple different packets, @@ -95,7 +64,7 @@ <table frame='all'> <title>Telemetry Packet Header</title> <tgroup cols='4' align='center' colsep='1' rowsep='1'> - <colspec align='right' colwidth='*' colname='Offset'/> + <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'/> @@ -172,10 +141,15 @@ 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='right' colwidth='*' colname='Offset'/> + <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'/> @@ -257,10 +231,18 @@ </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='right' colwidth='*' colname='Offset'/> + <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'/> @@ -324,10 +306,19 @@ </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='right' colwidth='*' colname='Offset'/> + <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'/> @@ -341,7 +332,8 @@ </thead> <tbody> <row> - <entry>5</entry><entry>uint8_t</entry><entry>flags</entry><entry>GPS Flags (see below)</entry> + <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> @@ -380,7 +372,8 @@ <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>N, A, D, E, M, S</entry> + <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> @@ -389,7 +382,7 @@ <entry>28</entry><entry>uint8_t</entry><entry>course</entry><entry>/ 2</entry> </row> <row> - <entry>29</entry><entry>uint8_t</entry><entry>unused[2]</entry> + <entry>29</entry><entry>uint8_t</entry><entry>unused[3]</entry> </row> <row> <entry>32</entry> @@ -397,6 +390,116 @@ </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> @@ -418,6 +521,15 @@ </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'> @@ -436,137 +548,183 @@ <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>uint8_t</entry><entry>sat_0_id</entry> + <entry>6</entry><entry>sat_info_t</entry><entry>sats[12]</entry> + <entry>See Per-Satellite data table below</entry> </row> <row> - <entry>7</entry><entry>uint8_t</entry><entry>sat_0_c_n_1</entry> + <entry>30</entry><entry>uint8_t</entry><entry>unused[2]</entry> </row> <row> - <entry>8</entry><entry>uint8_t</entry><entry>sat_1_id</entry> - </row> - <row> - <entry>9</entry><entry>uint8_t</entry><entry>sat_1_c_n_1</entry> - </row> - <row> - <entry>10</entry><entry>uint8_t</entry><entry>sat_2_id</entry> - </row> - <row> - <entry>11</entry><entry>uint8_t</entry><entry>sat_2_c_n_1</entry> - </row> - <row> - <entry>12</entry><entry>uint8_t</entry><entry>sat_3_id</entry> - </row> - <row> - <entry>13</entry><entry>uint8_t</entry><entry>sat_3_c_n_1</entry> - </row> - <row> - <entry>14</entry><entry>uint8_t</entry><entry>sat_4_id</entry> - </row> - <row> - <entry>15</entry><entry>uint8_t</entry><entry>sat_4_c_n_1</entry> - </row> - <row> - <entry>16</entry><entry>uint8_t</entry><entry>sat_5_id</entry> - </row> - <row> - <entry>17</entry><entry>uint8_t</entry><entry>sat_5_c_n_1</entry> - </row> - <row> - <entry>18</entry><entry>uint8_t</entry><entry>sat_6_id</entry> + <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>19</entry><entry>uint8_t</entry><entry>sat_6_c_n_1</entry> + <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>20</entry><entry>uint8_t</entry><entry>sat_7_id</entry> + <entry>0</entry><entry>uint8_t</entry><entry>svid</entry> + <entry>Space Vehicle Identifier</entry> </row> <row> - <entry>21</entry><entry>uint8_t</entry><entry>sat_7_c_n_1</entry> + <entry>1</entry><entry>uint8_t</entry><entry>c_n_1</entry> + <entry>C/N1 signal quality indicator</entry> </row> <row> - <entry>22</entry><entry>uint8_t</entry><entry>sat_8_id</entry> + <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>23</entry><entry>uint8_t</entry><entry>sat_8_c_n_1</entry> + <entry align='center'>Parameter</entry> + <entry align='center'>Value</entry> + <entry align='center'>Description</entry> </row> + </thead> + <tbody> <row> - <entry>24</entry><entry>uint8_t</entry><entry>sat_9_id</entry> + <entry>Modulation</entry> + <entry>GFSK</entry> + <entry>Gaussian Frequency Shift Keying</entry> </row> <row> - <entry>25</entry><entry>uint8_t</entry><entry>sat_9_c_n_1</entry> + <entry>Deviation</entry> + <entry>20.507812 kHz</entry> + <entry>Frequency modulation</entry> </row> <row> - <entry>26</entry><entry>uint8_t</entry><entry>sat_10_id</entry> + <entry>Data rate</entry> + <entry>38.360596 kBaud</entry> + <entry>Raw bit rate</entry> </row> <row> - <entry>27</entry><entry>uint8_t</entry><entry>sat_10_c_n_1</entry> + <entry>RX Filter Bandwidth</entry> + <entry>93.75 kHz</entry> + <entry>Receiver Band pass filter bandwidth</entry> </row> <row> - <entry>28</entry><entry>uint8_t</entry><entry>sat_11_id</entry> + <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>29</entry><entry>uint8_t</entry><entry>sat_11_c_n_1</entry> + <entry align='center'>Parameter</entry> + <entry align='center'>Value</entry> + <entry align='center'>Description</entry> </row> + </thead> + <tbody> <row> - <entry>30</entry><entry>uin8_t</entry><entry>unused30</entry> + <entry>Error Correction</entry> + <entry>Convolutional coding FEC</entry> + <entry>1/2 code, constraint length m=4</entry> </row> <row> - <entry>31</entry><entry>uin8_t</entry><entry>unused31</entry> + <entry>Interleaving</entry> + <entry>4 x 4</entry> + <entry>Reduce effect of noise burst</entry> </row> <row> - <entry>32</entry> + <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>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> - -<!-- - - - - - Rethinking this (over IRC), and thinking about telemetry from a - companion board, it looks like 32 bytes per packet would be better (12 - channels of A/D from telescience would require 24 bytes). - - Packet type 0x06: GPS satellites - 1 packet per second. - - - TeleScience - -<entry>5</entry><entry>uint8_t</entry><entry>channels</entry> -<entry>6</entry><entry>uint16_t</entry><entry>data[12]</entry> -<entry>30</entry><entry>uint8_t</entry><entry>unused[2]</entry> -<entry>32</entry> - - [ 2-line signature. Click/Enter to show. ] - - - - keith.packard@intel.com - [ application/pgp-signature ] - Keith Packard <keithp@keithp.com> (Mon. 18:59) (me sent) - Subject: Re: New telemetry ideas - To: bdale@gag.com - Date: Mon, 27 Jun 2011 18:59:08 -0700 - - [ multipart/signed ] - [ text/plain ] - On Mon, 27 Jun 2011 14:25:00 -0700, Keith Packard <keithp@keithp.com> wrote: - Non-text part: multipart/signed - - > Packet type 0x05: GPS location - > 1 packet per second - > - > 5 uint8_t flags - - Let's add another field here: - -<entry>6</entry><entry>int16_t</entry><entry>gps_tick</entry><entry>tick when GPS data was received</entry> - - That leaves a single byte unused --->
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