244 lines
13 KiB
Markdown
244 lines
13 KiB
Markdown
# Blackbox flight data recorder
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## Introduction
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This feature transmits your flight data information on every control loop iteration over a serial port to an external
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logging device to be recorded, or to a dataflash chip which is present on some flight controllers.
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After your flight, you can process the resulting logs on your computer to either turn them into CSV (comma-separated
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values) or render your flight log as a video using the tools `blackbox_decode` and `blackbox_render`. Those tools can be
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found in this repository:
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https://github.com/cleanflight/blackbox-tools
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You can also view your flight logs using your web browser with the interactive log viewer:
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https://github.com/cleanflight/blackbox-log-viewer
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## Logged data
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The blackbox records flight data on every iteration of the flight control loop. It records the current time in
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microseconds, P, I and D corrections for each axis, your RC command stick positions (after applying expo curves),
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gyroscope data, accelerometer data (after your configured low-pass filtering), barometer readings, 3-axis magnetometer
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readings, raw VBAT and current measurements, and the command being sent to each motor speed controller. This is all
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stored without any approximation or loss of precision, so even quite subtle problems should be detectable from the fight
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data log.
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GPS data is logged whenever new GPS data is available. Although the CSV decoder will decode this data, the video
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renderer does not yet show any of the GPS information (this will be added later).
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## Supported configurations
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The maximum data rate that can be recorded to the flight log is fairly restricted, so anything that increases the load
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can cause the flight log to drop frames and contain errors.
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The Blackbox was developed and tested on a quadcopter. It has also been tested on a tricopter. It should work on
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hexacopters or octocopters, but as they transmit more information to the flight log (due to having more motors), the
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number of dropped frames may increase. The `blackbox_render` tool only supports tri and quadcopters (please send me
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flight logs from other craft, and I can add support for them!)
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Cleanflight's `looptime` setting will decide how many times per second an update is saved to the flight log. The
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software was developed on a craft with a looptime of 2400. Any looptime smaller than this will put more strain on the
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data rate. The default looptime on Cleanflight is 3500.
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If you're using a looptime of 2300 or smaller, you will probably need to reduce the sampling rate in the Blackbox
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settings, or increase your logger's baudrate to 250000. See the later section on configuring the Blackbox feature for
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details.
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## Hardware
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There are two options for storing your flight logs. You can either transmit the log data over a serial port to an
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external logging device like the [OpenLog serial data logger][] to be recorded to a microSDHC card, or if you have a
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compatible flight controller you can store the logs on the onboard dataflash storage instead.
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### OpenLog serial data logger
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The OpenLog ships with standard OpenLog 3 firmware installed. However, in order to reduce the number of dropped frames,
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it should be reflashed with the [OpenLog Light firmware][] or the special [OpenLog Blackbox firmware][] (this needs to
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be version 2.0 or higher to allow configuration of baud rates).
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The Blackbox variant of the firmware ensures that the OpenLog is using the correct settings, and defaults to 115200
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baud. If you are using a looptime of 2500 or smaller, you should set the baud rate to 250000 instead to eliminate
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dropped frames.
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You can find the Blackbox version of the OpenLog firmware [here](https://github.com/cleanflight/blackbox-firmware),
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along with instructions for installing it onto your OpenLog.
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[OpenLog serial data logger]: https://www.sparkfun.com/products/9530
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[OpenLog Light firmware]: https://github.com/sparkfun/OpenLog/tree/master/firmware/OpenLog_v3_Light
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[OpenLog Blackbox firmware]: https://github.com/cleanflight/blackbox-firmware
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#### microSDHC
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Your choice of microSDHC card is very important to the performance of the system. The OpenLog relies on being able to
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make many small writes to the card with minimal delay, which not every card is good at. A faster SD-card speed rating is
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not a guarantee of better performance.
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##### microSDHC cards known to have poor performance
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- Generic 4GB Class 4 microSDHC card - the rate of missing frames is about 1%, and is concentrated around the most
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interesting parts of the log!
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- Sandisk Ultra 32GB (unlike the smaller 16GB version, this version has poor write latency)
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##### microSDHC cards known to have good performance
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- Transcend 16GB Class 10 UHS-I microSDHC (typical error rate < 0.1%)
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- Sandisk Extreme 16GB Class 10 UHS-I microSDHC (typical error rate < 0.1%)
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- Sandisk Ultra 16GB (it performs only half as well as the Extreme in theory, but still very good)
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You should format any card you use with the [SD Association's special formatting tool][] , as it will give the OpenLog
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the best chance of writing at high speed. You must format it with either FAT, or with FAT32 (recommended).
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[SD Association's special formatting tool]: https://www.sdcard.org/downloads/formatter_4/
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#### OpenLog configuration
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Power up the OpenLog with a microSD card inside, wait 10 seconds or so, then power it down and plug the microSD card
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into your computer. You should find a "CONFIG.TXT" file on the card. You should see the baud rate that the OpenLog has
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been configured to. You probably want this to be set to either 115200 (the default) or 250000 (for craft with looptimes
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smaller than 2500).
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Save the file and put the card back into your OpenLog, it should use those settings from now on.
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If your OpenLog didn't write a CONFIG.TXT file, create a CONFIG.TXT file with these contents and store it in the root
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of the MicroSD card:
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```
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115200
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baud
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```
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If you are using the official OpenLog Light firmware, use this configuration instead:
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```
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115200,26,0,0,1,0,1
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baud,escape,esc#,mode,verb,echo,ignoreRX
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```
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#### Serial port
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A hardware serial port is required to connect the OpenLog to your flight controller (such as `serial_port_1` on the
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Naze32, the two-pin Tx/Rx header in the center of the board). The Blackbox can not be used with softserial ports as they
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are too slow.
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Connect the "TX" pin of the serial port you've chosen to the OpenLog's "RXI" pin. Don't connect the serial port's RX
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pin to the OpenLog.
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#### Protection
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The OpenLog can be wrapped in black electrical tape or heat-shrink in order to insulate it from conductive frames (like
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carbon fiber), but this makes its status LEDs impossible to see. I recommend wrapping it with some clear heatshrink
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tubing instead.
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### Onboard dataflash storage
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Some flight controllers have an onboard SPI NOR flash chip which can be used to store flight logs instead of using an
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OpenLog.
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The full version of the Naze32 and the CC3D have an onboard "m25p16" 2 megayte dataflash storage chip. This is a small
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chip with 8 fat legs, which can be found at the base of the Naze32's direction arrow. This chip is not present on the
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"Acro" version of the Naze32.
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These chips are also supported:
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* Micron/ST M25P16 - 16 Mbit
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* Micron N25Q064 - 64 Mbit
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* Winbond W25Q64 - 64 Mbit
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## Enabling the Blackbox (CLI)
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In the [Cleanflight Configurator][] , enter the CLI tab. Enable the Blackbox feature by typing in `feature BLACKBOX` and
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pressing enter. Now choose the device that you want to log to:
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### OpenLog serial data logger
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Enter `set blackbox_device=0` to switch to logging to a serial port (this is the default).
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You then need to let Cleanflight know which of [your serial ports][] you connected the OpenLog to. A 115200 baud port
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is required (such as `serial_port_1` on the Naze32, the two-pin Tx/Rx header in the center of the board).
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You can use the GUI to configure a port for the Blackbox feature on the Ports tab.
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### Onboard dataflash
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Enter `set blackbox_device=1` to switch to logging to an onboard dataflash chip, if your flight controller has one.
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[your serial ports]: https://github.com/cleanflight/cleanflight/blob/master/docs/Serial.md
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[Cleanflight Configurator]: https://chrome.google.com/webstore/detail/cleanflight-configurator/enacoimjcgeinfnnnpajinjgmkahmfgb?hl=en
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## Configuring the Blackbox
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If you are using a short looptime like 2500 or smaller, try switching your OpenLog to 250000 baud (instead of the
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default of 115200) and set that baud rate on the Blackbox's port in the Confgurator.
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The Blackbox currently provides two settings (`blackbox_rate_num` and `blackbox_rate_denom`) that allow you to control
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the rate at which data is logged. These two together form a fraction (`blackbox_rate_num / blackbox_rate_denom`) which
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decides what portion of the flight controller's control loop iterations should be logged. The default is 1/1 which logs
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every iteration.
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If you're using a slower MicroSD card, you may need to reduce your logging rate to reduce the number of corrupted
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logged frames that `blackbox_decode` complains about. A rate of 1/2 is likely to work for most craft.
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You can change the logging rate settings by entering the CLI tab in the [Cleanflight Configurator][] and using the `set`
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command, like so:
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```
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set blackbox_rate_num = 1
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set blackbox_rate_denom = 2
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```
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The data rate for my quadcopter using a looptime of 2400 and a rate of 1/1 is about 10.25kB/s. This allows about 18
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days of flight logs to fit on my OpenLog's 16GB MicroSD card, which ought to be enough for anybody :).
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If you're logging to an onboard dataflash chip instead of an OpenLog, be aware that the 2MB of storage space it offers
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is pretty small. At the default 1/1 logging rate, and a 2400 looptime, this is only enough for about 3 minutes of
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flight. This could be long enough for you to investigate some flying problem with your craft, but you may want to reduce
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the logging rate in order to extend your recording time.
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To maximize your recording time, you could drop the rate way down to 1/32 (the smallest possible rate) which would
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result in a logging rate of about 10-20Hz and about 650 bytes/second of data. At that logging rate, the 2MB flash chip
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can store around 50 minutes of flight data, though the level of detail is severely reduced and you could not diagnose
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flight problems like vibration or PID setting issues.
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## Usage
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The Blackbox starts recording data as soon as you arm your craft, and stops when you disarm.
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If your craft has a buzzer attached, a short beep will be played when you arm and recording begins. You can later use
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this beep to synchronize your recorded flight video with the rendered flight data log (the beep is shown as a blue line
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in the flight data log, which you can sync against the beep in your recorded audio track).
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You should wait a few seconds after disarming your craft to allow the Blackbox to finish saving its data.
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### Usage - OpenLog
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Each time the OpenLog is power-cycled, it begins a fresh new log file. If you arm and disarm several times without
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cycling the power (recording several flights), those logs will be combined together into one file. The command line
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tools will ask you to pick which one of these flights you want to display/decode.
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Don't insert or remove the SD card while the OpenLog is powered up.
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### Usage - Dataflash chip
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After your flights, you can use the [Cleanflight Configurator][] to download the contents of the dataflash to your
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computer. Go to the "dataflash" tab and click the "save flash to file..." button. Saving the log can take 2 or 3
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minutes.
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After downloading the log, be sure to erase the chip to make it ready for reuse by clicking the "erase flash" button.
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If you try to start recording a new flight when the dataflash is already full, the Blackbox will not make its regular
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arming beep and nothing will be recorded.
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## Converting logs to CSV or PNG
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After your flights, you'll have a series of flight log files with a .TXT extension. You'll need to decode these with
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the `blackbox_decode` tool to create CSV (comma-separated values) files for analysis, or render them into a series of PNG
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frames with `blackbox_render` tool, which you could then convert into a video using another software package.
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You'll find those tools along with instructions for using them in this repository:
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https://github.com/cleanflight/blackbox-tools
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You can also view your .TXT flight log files interactively using your web browser with the Cleanflight Blackbox Explorer
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tool:
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https://github.com/cleanflight/blackbox-log-viewer
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This allows you to scroll around a graphed version of your log and examine your log in detail. |