libraries/AP_Logger/README.md
The format type specifies the amount of storage required for the entry and how the content should be interpreted.
| Char | C Type |
|---|---|
| a | int16_t[32] |
| b | int8_t |
| B | uint8_t |
| h | int16_t |
| H | uint16_t |
| i | int32_t |
| I | uint32_t |
| f | float |
| d | double |
| n | char[4] |
| N | char[16] |
| Z | char[64] |
| L | int32_t latitude/longitude (so -35.1332423 becomes -351332423) |
| M | uint8_t flight mode |
| q | int64_t |
| Q | uint64_t |
| g | float16_t |
Legacy field types - do not use. These have been replaced by using the base C type and an appropriate multiplier column entry.
| Char | CType+Mult |
|---|---|
| c | int16_t * 100 |
| C | uint16_t * 100 |
| e | int32_t * 100 |
| E | uint32_t * 100 |
All units here should be base units. This means battery capacity uses "amp * second" not "milliAmp * hours". Please keep the names consistent with Tools/autotest/param_metadata/param.py:33
| Char | Unit Abbrev. | Description | Notes |
|---|---|---|---|
| '-' | "" | no units e.g. Pi or a string | |
| '?' | "UNKNOWN" | Units which haven't been worked out yet.... | |
| 'A' | "A" | Ampere | |
| 'd' | "deg" | of the angular variety | -180 to 180 |
| 'b' | "B" | bytes | |
| 'B' | "B/s" | bytes per second | |
| 'k' | "deg/s" | degrees per second | Not an SI unit, but in some situations more user-friendly than radians per second |
| 'D' | "deglatitude" | degrees of latitude | |
| 'e' | "deg/s/s" | degrees per second per second | Not an SI unit, but in some situations more user-friendly than radians per second^2 |
| 'E' | "rad/s" | radians per second | |
| 'G' | "Gauss" | Gauss | Not an SI unit, but 1 tesla = 10000 gauss so a simple replacement is not possible here |
| 'h' | "degheading" | 0.? to 359.? | |
| 'i' | "A.s" | Ampere second | |
| 'J' | "W.s" | Joule (Watt second) | |
| 'l' | "l" | litres | |
| 'L' | "rad/s/s" | radians per second per second | |
| 'm' | "m" | metres | |
| 'n' | "m/s" | metres per second | |
| 'N' | "N" | Newton | |
| 'o' | "m/s/s" | metres per second per second | |
| 'O' | "degC" | degrees Celsius | Not an SI unit, but Kelvin is too cumbersome for most users |
| '%' | "%" | percent | |
| 'S' | "satellites" | number of satellites | |
| 's' | "s" | seconds | |
| 'q' | "rpm" | revolutions per minute | Not an SI unit, but sometimes more intuitive than Hertz |
| 'r' | "rad" | radians | |
| 't' | "N.m" | Newton meters | torque |
| 'U' | "deglongitude" | degrees of longitude | |
| 'u' | "ppm" | pulses per minute | |
| 'v' | "V" | Volt | |
| 'P' | "Pa" | Pascal | |
| 'w' | "Ohm" | Ohm | |
| 'W' | "W" | watt | |
| 'X' | "W.h" | watt hour | |
| 'Y' | "us" | pulse width modulation in microseconds | |
| 'z' | "Hz" | Hertz | |
| '#' | "instance" | (e.g.)Sensor instance number |
This multiplier information applies to the raw value present in the log. Any adjustment implied by the format field (e.g. the "centi" in "centidegrees" is IGNORED for the purposes of scaling. Essentially "format" simply tells you the C-type, and format-type h (int16_t) is equivalent to format-type c (int16_t*100) tl;dr a GCS shouldn't/mustn't infer any scaling from the unit name
| Char | Multiplier | Description |
|---|---|---|
| '-' | 0 | no multiplier e.g. char[4] |
| '?' | 1 | multipliers which haven't been worked out yet |
| '2' | 1e2 | |
| '1' | 1e1 | |
| '0' | 1e0 | x1 |
| 'A' | 1e-1 | |
| 'B' | 1e-2 | |
| 'C' | 1e-3 | |
| 'D' | 1e-4 | |
| 'E' | 1e-5 | |
| 'F' | 1e-6 | |
| 'G' | 1e-7 | |
| 'I' | 1e-9 | |
| '!' | 3.6 | (milliampere * hour => ampere * second) and (km/h => m/s) |
| '/' | 3600 | (ampere * hour => ampere * second) |