OrangePI PC with Buildroot and Linux-4.9 (LinuxFlight)

The OrangePI PC booting/working with 4.9-rc1.  This is possible due to https://github.com/megous/linux/tree/orange-pi-4.9 github project.

[    0.000000] Linux version 4.9.0-rc1 (tcmichals@tcmichals-Studio-540) (gcc version 5.4.0 (Buildroot 2016.11-git-01024-g731b3c5) ) #6

So far have tested:

• Ethernet works
• I2C works.
• THS works
• Added some patches to SPI  Instead of using the entire patch, just changed the FIFO to 64 and added DT changes.  Also changed spidev.c and added:

static const struct of_device_id spidev_dt_ids[] = {

{ .compatible = "rohm,dh2228fv" },

{ .compatible = "lineartechnology,ltc2488" },

        { .compatible = "spidev" },  //TCM:FIX 

One issue just encountered several days ago is how to run Java; the solution is Java SE embedded.  Just follow the instructions here.

# java -version

java version "1.8.0_111"

Java(TM) SE Embedded Runtime Environment (build 1.8.0_111-b14, profile compact1, headless)

Java HotSpot(TM) Embedded Client VM (build 25.111-b14, mixed mode)

The goal of LinuxFlight is to be able to run Java, Python and C++ plugins/modules.  Pieces of the flight code can be offloaded to other modules, or to different programming languages. 

The current goal is to use Python to load and "wire" modules, with additional configuration.  This allows:

• First module, will be GPS.  All of the parsing and configuration of the GPS will be written in python and calls into the Flight controller software.  Now, different GPS modules can be added using python. 

LinuxFlight connecting to CleanFlight Configurator

Just finished updating github LinuxFlight.  CleanFlight Configurator, is not able to connect and start sending MSP packets; but something is hanging up in getting data messages.  Work on that next week.

How to build LinuxFlight (Linux only):

• Need to build boost C++ libraries and install them 
• make
• ./PC
• open another terminal 
•  socat -d -d pty,raw,echo=0 tcp:localhost:56000
• This will create a pty, the output from socat show which pty to connect configurator
• i.e /dev/pts/9

There is a lot to do to improve the IPC speed, i.e not to copy std::vector, but to use std::move, so there is no copy.  Also, move the IPC queue struct from std::queue to boost::lockfree::queue with a semaphore to wake up the FC thread.  

The heart of the IPC is a send-reply via std::function<void (void)> type function.  So, how can a void function be able to process arguments and do process callbacks?  

• Use std::bind, this arguments.   For example, in  mspSerialTCPPort.h,  function: handle_read creates a std::function<void (void)> 

                  msgPost_t _msg;
                  mspCallback_t _callback = std::bind(&mspSerialTCPClient::postHandleWrite,                                                                                            shared_from_this(),                                                                                                                                std::placeholders::_1);

                  _msg.m_in = std::bind(&callToMSPFromTCP, _pkt, _callback);

So, msgPost_t is created with a function callback.  The std::bind takes the packet and places it in one of the arguments.  Along with a call back function.  It is important to use shared_ptr, so the class does not disappear until all callbacks are completed. So, when the function is invoked the arguments are unpacked and the MSP function is call.

This is a simple way, to keep a callback IPC API and allow any type of arguments.  Yes, it is confusing, but look at the code, run it and debug it. 

So, the current design is to move most of the I/O from the flight controller main thread, this way I2C. serial, etc are processed out side of the thread.  All data will be posted to the FC thread, this way, this should minimize jitter.  

LinuxFlight github

After several rounds of code porting and trying to keep the code compatible with a micro-controller decided to just move to Linux only port.

The goal is to keep the main Flight-Controller loop reads accelerometer, and gyro, and move the reset of the I/O to read threads.  This way keeps the main loop on time.

Also, the Neo Air is out, so, that will be the FC board with I/O processor.

• ARM Linux board
• GPS (Serial)
• MS5611  (I2C)
• MPU9250 (SPI)
• I/O processor (USB)
• MSP via TCP/IP
• RX (Need to validate and test serial Ports are able to handle iBUS, or sBUS)
• I/O processor
• RX (PWM or Serial)
• Telemetry
• PWM out (motor control)

So, go, but making progress..