X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=AltOS%2Fdoc%2Ftelemetry.html;h=4dfb659b80a8cc8ab73eb2184dde643a234444d5;hb=2456b44fd8431101c8e9dc1feffc2890a7c5d96a;hp=c639ea0ab49b9920dbeef1e8818db8119083c8c4;hpb=3259723cf5b3b5d1e1c825cc00a4a16b255414da;p=web%2Faltusmetrum diff --git a/AltOS/doc/telemetry.html b/AltOS/doc/telemetry.html index c639ea0..4dfb659 100644 --- a/AltOS/doc/telemetry.html +++ b/AltOS/doc/telemetry.html @@ -1,10 +1,10 @@ -
Copyright © 2011 Keith Packard
+
Copyright © 2011 Keith Packard
This document is released under the terms of the Creative Commons ShareAlike 3.0 license. -
Revision History | |
---|---|
Revision 0.1 | 01 July 2011 |
Initial content |
Table of Contents
Revision History | |
---|---|
Revision 0.1 | 01 July 2011 |
Initial content |
Table of Contents
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 @@ -22,14 +22,14 @@ 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. -
Table 1. Telemetry Packet Header
Offset | Data Type | Name | Description |
---|---|---|---|
0 | uint16_t | serial | Device serial Number |
2 | uint16_t | tick | Device time in 100ths of a second |
4 | uint8_t | type | Packet type |
5 |
+
+ This section first defines the packet header common to all packets + and then the per-packet data layout. +
Table 1. Telemetry Packet Header
Offset | Data Type | Name | Description |
---|---|---|---|
0 | uint16_t | serial | Device serial Number |
2 | uint16_t | tick | Device time in 100ths of a second |
4 | uint8_t | type | Packet type |
5 |
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. -
Type | Description |
---|---|
0x01 | TeleMetrum Sensor Data |
0x02 | TeleMini Sensor Data |
0x03 | TeleNano Sensor Data |
+
Type | Description |
---|---|
0x01 | TeleMetrum Sensor Data |
0x02 | TeleMini Sensor Data |
0x03 | TeleNano Sensor Data |
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 @@ -38,63 +38,63 @@ 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 -
Table 2. Sensor Packet Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | state | Flight state |
6 | int16_t | accel | accelerometer (TM only) |
8 | int16_t | pres | pressure sensor |
10 | int16_t | temp | temperature sensor |
12 | int16_t | v_batt | battery voltage |
14 | int16_t | sense_d | drogue continuity sense (TM/Tm) |
16 | int16_t | sense_m | main continuity sense (TM/Tm) |
18 | int16_t | acceleration | m/s² * 16 |
20 | int16_t | speed | m/s * 16 |
22 | int16_t | height | m |
24 | int16_t | ground_pres | Average barometer reading on ground |
26 | int16_t | ground_accel | TM |
28 | int16_t | accel_plus_g | TM |
30 | int16_t | accel_minus_g | TM |
32 |
Type | Description |
---|---|
0x04 | Configuration Data |
+
Table 2. Sensor Packet Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | state | Flight state |
6 | int16_t | accel | accelerometer (TM only) |
8 | int16_t | pres | pressure sensor |
10 | int16_t | temp | temperature sensor |
12 | int16_t | v_batt | battery voltage |
14 | int16_t | sense_d | drogue continuity sense (TM/Tm) |
16 | int16_t | sense_m | main continuity sense (TM/Tm) |
18 | int16_t | acceleration | m/s² * 16 |
20 | int16_t | speed | m/s * 16 |
22 | int16_t | height | m |
24 | int16_t | ground_pres | Average barometer reading on ground |
26 | int16_t | ground_accel | TM |
28 | int16_t | accel_plus_g | TM |
30 | int16_t | accel_minus_g | TM |
32 |
Type | Description |
---|---|
0x04 | Configuration Data |
This provides a description of the software installed on the flight computer as well as any user-specified configuration data.
Configuration data packets are transmitted once per second during all phases of the flight -
Table 3. Sensor Packet Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | type | Device type |
6 | uint16_t | flight | Flight number |
8 | uint8_t | config_major | Config major version |
9 | uint8_t | config_minor | Config minor version |
10 | uint16_t | apogee_delay | Apogee deploy delay in seconds |
12 | uint16_t | main_deploy | Main deploy alt in meters |
14 | uint16_t | flight_log_max | Maximum flight log size (kB) |
16 | char | callsign[8] | Radio operator identifier |
24 | char | version[8] | Software version identifier |
32 |
Type | Description |
---|---|
0x05 | GPS Location |
+
Table 3. Sensor Packet Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | type | Device type |
6 | uint16_t | flight | Flight number |
8 | uint8_t | config_major | Config major version |
9 | uint8_t | config_minor | Config minor version |
10 | uint16_t | apogee_delay | Apogee deploy delay in seconds |
12 | uint16_t | main_deploy | Main deploy alt in meters |
14 | uint16_t | flight_log_max | Maximum flight log size (kB) |
16 | char | callsign[8] | Radio operator identifier |
24 | char | version[8] | Software version identifier |
32 |
Type | Description |
---|---|
0x05 | GPS Location |
This packet provides all of the information available from the Venus SkyTraq GPS receiver—position, time, speed and precision estimates.
GPS Location packets are transmitted once per second during all phases of the flight -
Table 4. GPS Location Packet Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | flags | See GPS Flags table below |
6 | int16_t | altitude | m |
8 | int32_t | latitude | degrees * 107 |
12 | int32_t | longitude | degrees * 107 |
16 | uint8_t | year | |
17 | uint8_t | month | |
18 | uint8_t | day | |
19 | uint8_t | hour | |
20 | uint8_t | minute | |
21 | uint8_t | second | |
22 | uint8_t | pdop | * 5 |
23 | uint8_t | hdop | * 5 |
24 | uint8_t | vdop | * 5 |
25 | uint8_t | mode | See GPS Mode table below |
26 | uint16_t | ground_speed | cm/s |
28 | int16_t | climb_rate | cm/s |
30 | uint8_t | course | / 2 |
31 | uint8_t | unused[1] | |
32 |
+
Table 4. GPS Location Packet Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | flags | See GPS Flags table below |
6 | int16_t | altitude | m |
8 | int32_t | latitude | degrees * 107 |
12 | int32_t | longitude | degrees * 107 |
16 | uint8_t | year | |
17 | uint8_t | month | |
18 | uint8_t | day | |
19 | uint8_t | hour | |
20 | uint8_t | minute | |
21 | uint8_t | second | |
22 | uint8_t | pdop | * 5 |
23 | uint8_t | hdop | * 5 |
24 | uint8_t | vdop | * 5 |
25 | uint8_t | mode | See GPS Mode table below |
26 | uint16_t | ground_speed | cm/s |
28 | int16_t | climb_rate | cm/s |
30 | uint8_t | course | / 2 |
31 | uint8_t | unused[1] | |
32 |
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. -
Table 5. GPS Flags
Bits | Name | Description |
---|---|---|
0-3 | nsats | Number of satellites in solution |
4 | valid | GPS solution is valid |
5 | running | GPS receiver is operational |
6 | date_valid | Reported date is valid |
7 | course_valid | ground speed, course and climb rates are valid |
+
Table 5. GPS Flags
Bits | Name | Description |
---|---|---|
0-3 | nsats | Number of satellites in solution |
4 | valid | GPS solution is valid |
5 | running | GPS receiver is operational |
6 | date_valid | Reported date is valid |
7 | course_valid | ground speed, course and climb rates are valid |
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. -
Table 6. GPS Mode
Type | Description |
---|---|
0x06 | GPS Satellite Data |
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.
GPS Satellite data are transmitted once per second during all phases of the flight. -
Table 7. GPS Satellite Data Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | channels | Number of reported satellite information |
6 | sat_info_t | sats[12] | See Per-Satellite data table below |
30 | uint8_t | unused[2] | |
32 |
Table 8. GPS Per-Satellite data (sat_info_t)
Offset | Data Type | Name | Description |
---|---|---|---|
0 | uint8_t | svid | Space Vehicle Identifier |
1 | uint8_t | c_n_1 | C/N1 signal quality indicator |
2 |
+
Table 7. GPS Satellite Data Contents
Offset | Data Type | Name | Description |
---|---|---|---|
5 | uint8_t | channels | Number of reported satellite information |
6 | sat_info_t | sats[12] | See Per-Satellite data table below |
30 | uint8_t | unused[2] | |
32 |
Table 8. GPS Per-Satellite data (sat_info_t)
Offset | Data Type | Name | Description |
---|---|---|---|
0 | uint8_t | svid | Space Vehicle Identifier |
1 | uint8_t | c_n_1 | C/N1 signal quality indicator |
2 |
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. -
+
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: -
Table 9.
Parameter | Value | Description |
---|---|---|
Modulation | GFSK | Gaussian Frequency Shift Keying |
Deviation | 20.507812 kHz | Frequency modulation |
Data rate | 38.360596 kBaud | Raw bit rate |
RX Filter Bandwidth | 93.75 kHz | Receiver Band pass filter bandwidth |
IF Frequency | 140.62 kHz | Receiver intermediate frequency |
+
Table 9. Modulation Scheme
Parameter | Value | Description |
---|---|---|
Modulation | GFSK | Gaussian Frequency Shift Keying |
Deviation | 20.507812 kHz | Frequency modulation |
Data rate | 38.360596 kBaud | Raw bit rate |
RX Filter Bandwidth | 93.75 kHz | Receiver Band pass filter bandwidth |
IF Frequency | 140.62 kHz | Receiver intermediate frequency |
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. -
Table 10.
Parameter | Value | Description |
---|---|---|
Error Correction | Convolutional coding FEC | 1/2 code, constraint length m=4 |
Interleaving | 4 x 4 | Reduce effect of noise burst |
Data Whitening | XOR with 9-bit PNR | Rotate right with bit 8 = bit 0 xor bit 5, initial - value 111111111 |
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, @@ -106,9 +106,9 @@ 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. -
Table 11.
Offset | Name | Example | Description | ||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 | length | 22 | Total length of data bytes in the line. Note that
+ Table 11. Packet Format
| ||||||||||||||||||||||||
length | checksum | 88 | (0x5a + sum(bytes 1 ·· length-1)) % 256 |