Blackbox Library

The Blackbox library is a port (modification) of the Blackbox implementation by Nicholas Sherlock (aka thenickdude), see https://github.com/thenickdude/blackbox It also contains Kustaa Nyholm's printf implementation. This library is written C++. (The original was written in C).

The main changes in this library are:

1. Code has been converted to C++.
2. Dependencies (ie configs, features, sensors etc) have been removed and abstracted into callbacks, so this library can be used on its own.

Notes on Blackbox tasks and scheduling

Betaflight uses non-preemptive cooperative scheduling. This means tasks undertake activities that take a long time need to yield while undertaking those activities. Betaflight uses two common design patterns to do this:

1. Splitting an activity into reasonable chunks and using a state machine to sequence through those chunks.
2. Making asynchronous calls to a function with a callback for when that function completes.

In Betaflight, Blackbox runs as a subtask of the MainPidLoop task, which typically runs at 8kHz. Blackbox can be configured to run at a submultiple of that frequency (ie 4kHz, 2kHz, etc).

Notes on the port

This is very much a "minimal effort" port - just enough work was done to get it working for ProtoFlight and SelfBalancingRobot.

This means the code is a curious mix of both my style and the original style. It is also a curious mix of C-like code and C++-like code.

License Information

This library is a port (modification) of the Blackbox implementation by Nicholas Sherlock (aka thenickdude), source code. This was licensed under the GNU GPL v3.

This library also contains Kustaa Nyholm's printf implementation, which is included under the terms of its license and includes that implementation's copyright notice, conditions and disclaimer.

Simplified Class Diagram

All writing to the serial device is done via the BlackboxEncoder

classDiagram
    class BlackboxEncoder {
        write(uint8_t value)
    }
    class Blackbox {
        <<abstract>>
        writeSystemInformation() write_e *
        virtual update() uint32_t
    }
    class BlackboxCallbacksBase {
        <<abstract>>
        loadSlowState() *
        loadMainState() *
    }
    class MessageQueueBase {
        <<abstract>>
        WAIT const int32_t *
    }
    class BlackboxSerialDevice {
        <<abstract>>
    }
    class BlackboxSerialDeviceSDCard["BlackboxSerialDeviceSDCard(eg)"]

    Blackbox o-- BlackboxCallbacksBase : calls loadState
    Blackbox *-- BlackboxEncoder : calls write
    BlackboxEncoder o-- BlackboxSerialDevice : calls write
    Blackbox o-- BlackboxSerialDevice : calls open close
    %%BlackboxSerialDevice --o BlackboxEncoder : calls write
    BlackboxSerialDevice <|-- BlackboxSerialDeviceSDCard

    TaskBase <|-- BlackboxTask
    class BlackboxTask {
        +loop()
        -task() [[noreturn]]
    }
    BlackboxTask o-- MessageQueueBase : calls WAIT
    BlackboxTask o-- Blackbox : calls update

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