mirror of https://github.com/ArduPilot/ardupilot
333 lines
12 KiB
Plaintext
333 lines
12 KiB
Plaintext
2013-09-23
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These notes describe the steps take to port ArduPilot to the Flymaple platform
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http://www.open-drone.org/flymaple
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Flymaple has an ARM based Cortex-3 STM32F103RE, 72MHz processor with 10DOF builtin sensors
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Implementation
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Unlike the Arduino versions of ardupilot, the Flymaple port uses portions of a
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custom version of the libmaple library, including the stm32f1 core and some
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other libaries like Wire, HardwareTimer, HArdwareSPI etc.
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Most of the changes are confined to new directory libraries/AP_HAL_FLYMAPLE
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which contains the Flymaple specific code. All the HAL modules have
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been ported, sometimes based on HAL_AVR, sometimes HAL_PX4:
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AnalogIn
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AnalogSource
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Console
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GPIO
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I2CDriver
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RCInput
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RCOoutput
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Scheduler
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Semaphores
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SPIDriver
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Storage
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UARTDriver
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Utility
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The implementation of Storage uses EEPROM emulation code that uses 2 pages of
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Flymaple FLASH ROM as EEPROM. It was copied from
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AeroQuad_v3.2 to libraries/AP_HAL_FLYMAPLE/utility and slightly modified:
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libraries/AP_HAL_FLYMAPLE/utility/EEPROM.*
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libraries/AP_HAL_FLYMAPLE/utility/flash_stm32.*
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Unlike other HAL ports, the namespace for Flymaple defined in
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AP_HAL_FLYMAPLE_Namespace.h has a more extensive name: 'AP_HAL_FLYMAPLE_NS' else
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get complaints from gcc 4.4.1 caused by collisions with other class names.
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New board makefile mk/board/flymaple.mk, plus some other minor changes in
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mk/*.mk
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In other parts of the ardupilot tree, the changes have been #ifdefed for
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Flymaple:
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- libraries/AP_Compass/AP_Compass_HMC5843.cpp
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- libraries/AP_Compass/Compass.h
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- libraries/AP_Baro/AP_Baro_BMP085.cpp
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Minor changes to raw data fetches to make them 32bit compatible. Should not
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affect other platforms.
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Some other minor edits to eliminate compiler warnings
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These changes have now all been included in the ardupilot mainline code.
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Resource usage
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Resources on the Flymaple board have been allocated by the HAL:
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Pins
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0 AP GPS on Flymaple Serial2 Rx in. This is where you connect the
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GPS. 3.3V input only, NOT 5V tolerant, use a voltage divider for 5V GPSs.
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1 AP GPS on Flymaple Serial2 Tx out. This is where you connect the GPS.
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3.3V output
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5 I2C SCL. Do not use for GPIO.
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6 Receiver PPM-SUM in.
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7 Console and Mavlink on Flymaple Serial1 Rx in. Also on connector
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"COM1". 5V input tolerant.
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8 Console and Mavlink on Flymaple Serial1 Tx out. Also on connector
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"COM1". 3.3V output.
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9 I2C SDA. Do not use for GPIO
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15 3.3V board VCC analog in. Connect to 3.3V pin.
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16 Airspeed analog in (if available). 3.3V, NOT 5V tolerant.
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19 Battery current analog in (if available). 3.3V, NOT 5V tolerant.
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20 Battery voltage analog in (on-board divider connected to board VIN)
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29 Telemetry Tx to radio on Serial3 on connector labelled "GPS". 3.3V output
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30 Telemetry Rx from radio on Serial3 on connector labelled "GPS". 5V input tolerant.
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Timers
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SysTick 1000Hz normal timers
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1 CH1 RCInput
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2 CH1 1000Hz Failsafe timer
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3 CH1-4, 4 CH1-2 RCOut
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8 not used by AP
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The I2CDriver on Flymaple uses the libmaple i2c low level hardware I2C
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library, configuredfor high speed (400kHz).
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As at 2013-10-03, there is a bug in the libmaple git master code, that causes
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a crash in the I2C interrupt handler. Therfore it is necessary to use the
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patched version of libmaple referred to below.
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At 400kHz I2C speed, it takes 500us to read both the 6 byte accelerometer
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buffer and the the 6 byte gyro buffer.
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The SerialUSB (USB connection) to Flymaple is not used by AP. It can be used for
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debugging inside AP_HAL_FLYMAPLE, using SerialUSB.println().
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Sensor configuration
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The sensors are configured so:
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ADXL345 Accelerometer
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8g full scale, full resolution mode, 800Hz bandwidth, read at 1kHz sample rate
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ITG3205 Gyro
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2000 degrees/sec, 256Hz LPF, 8kHz internal sample rate, read at 1kHz sample rate
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The gyro and accelerometers are sampled at about 800Hz in
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AP_InertialSensor_Flymaple.cpp, with the samples passed through a software
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2-pole low pass filter, to produce filtered data for the main loop.
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Installation on Linux
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Tested with:
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- libmaple patched library based on https://github.com/leaflabs/libmaple (see
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below for more data)
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- http://leaflabs.com/docs/unix-toolchain.html
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- arm-none-eabi-g++ toolchain, version 4.4.1
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on OpenSuSE 12.3
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Mission Planner 1.2.78
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You need a number of additional resources to build ardupilot for Flymaple. I
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have assumed that you will install them in your home directory, but they can really
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go anywhere provided you make the appropriate changes to PATH and config.mk
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cd ~
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git clone https://github.com/mikemccauley/libmaple.git
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cd libmaple
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wget http://static.leaflabs.com/pub/codesourcery/gcc-arm-none-eabi-latest-linux32.tar.gz
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tar xvzf gcc-arm-none-eabi-latest-linux32.tar.gz
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export PATH=$PATH:~/libmaple/arm/bin
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cp main.cpp.example main.cpp
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make
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(at this stage you can test your flymaple CPU and the upload process with
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'make install', which will upload a simple LED blinking program to your
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Flymaple)
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Now download ardupilot:
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cd ~
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git clone https://github.com/ArduPilot/ardupilot.git
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cd ardupilot
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edit config.mk to be something like:
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#config.mk START
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# Select maple_RET6 for Flymaple
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BOARD = maple_RET6
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# HAL_BOARD determines default HAL target.
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HAL_BOARD ?= HAL_BOARD_FLYMAPLE
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# The communication port used to communicate with the Flymaple
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PORT = /dev/ttyACM0
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# You must provide the path to the libmaple library directory:
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LIBMAPLE_PATH = $(HOME)/libmaple
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# Also, the ARM compiler tools MUST be in your current PATH like:
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# export PATH=$PATH:~/libmaple/arm/bin
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#config.mk END
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cd ArduPlane
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make flymaple
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make upload
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Libmaple fork
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Correct compilation and operation of the Flymaple port depends on
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using the fork of libmaple from https://github.com/mikemccauley/libmaple.git
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The changes relative to the libmaple master are:
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- Add LIBMAPLE_VERSION_MAJOR and LIBMAPLE_VERSION_MINOR for version detection
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- Add TX ring buffer and interrupt handler to usart.c
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- Fix a bug in I2C interrupt handler that would crash in master mode
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Interrupt disabling on ARM
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On AVR, ISRs run by default with the global interrupt enable flag disabled,
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whereas mainline code runs by default with global interrupt enable flag
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*enabled*. Which means that cli()/sei() in an ISR will have a different effect
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to cli()sei() in mainline code. Thats why code that *might* run in an ISR must
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use the special idiom: so that it restores the flag to the state it was before
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the critical block
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On ARM, the global interrupt disable flag PRIMASK is not altered behind your
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back by hardware. By default its always clear (ie enabled) even in ISRs. A
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different mechanism prevents ISRs from being reinterrupted. This means that
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non-nested noInterrupts()/interrupts() will always leave the PRIMASK as it was
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(interrupts enabled) when the critical block started, whether in ISRs or
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mainline code.
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Conclusion:
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On AVR, cli()/sei() is dangerous both in ISRs *and* when nested.
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On ARM, noInterrupts()/interrupts() is only dangerous when nested.
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Sensor Orientation
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The Flymaple board has no clear indication about which way is meant to be
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'forward' or 'right', so we have adopted the following convention:
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Aircraft 'Forward' is in the direction of the arrow marked 'Pitch' on the board, ie
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towards pin 0.
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Aircraft 'Right' is towards the bottom right corner of the board, towards pin 20 and
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the 5V regulator
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Aircraft 'Down' is away from the copper side of the board: 'right way up' is with
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component side up.
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Here in SE Queensland, in the southern hemisphere, the local mag field is
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substantially vertical (down? is that correct?), and so the following simple
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tests of the board should give the following results, using the mavproxy
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graphing tools, and with a board orientation parameter of none:
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The aircraft coordinate system of ardupilot is:
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X +ve forward
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Y +ve right
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Z +ve down
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Compass
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Orientation Results
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Level, right way up Z -ve
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Left side down Y +ve
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Nose up X +ve
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(ie positive when that axis is pointing away from the earth, at least where I
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am)
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Accelerometer
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Orientation Results
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Level, right way up Z -ve
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Left side down Y +ve
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Nose up X +ve
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(ie positive when that axis is pointing away from the earth, and consistent
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with compass in southern hemisphere)
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Gyro
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Rotation Results
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Yawing to right Z +ve
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Rolling to right X +ve
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Pitching up Y +ve
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(ie right hand curl rule relative to the given axis)
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Alternative Orientations
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Although the default board orientation is as described above, you can alter it
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by changing the AHRS_ORIENTATION parameter.
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For example, if you set AHRS_ORIENTATION to 1 (Yaw45), then the board will act
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as if 'Forward' is towards the green row of pin headers (ie the row of digital
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input pins marked 0 to 13, and 'Right' is towards the triple row of pins
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marked PWM. This orientation is good for vehicles where the board must be
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orthogonal to the direction of movement.
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PPM-SUM receiver and transmitter channel assignments
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Pin 6 of the Flymaple is used for the PPM-SUM receiver input
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I used the DSM2 PPM+UART receiver product code LEM-CH6-PPM from www.lemon-rx.com:
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http://www.lemon-rx.com/shop/index.php?route=product/product&path=70&product_id=66
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(make sure you use one made after Oct 2013: earlier versions had a proprietary and
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incompatible PPM output).
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The raw channel numbers resulting from using this with my Spektrum DX6i 6
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channel mode 2 transmitter are:
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Channel Assignment
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1 Throttle
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2 Aileron/Roll
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3 Elevator/Pitch
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4 Rudder/Yaw
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5 Gear/mode
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6 Flap/learn
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With the following channels configured for APMrover:
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RCMAP_PITCH 1
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RCMAP_ROLL 2
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RCMAP_THROTTLE 3
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RCMAP_YAW 4
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MODE_CH 5
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LEARN_CH 6
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with the RC servo ouputs on Flymaple J5:
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Transmitter channel 2 (steering) PWM/AIN/D27
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Transmitter channel 3 (speed = motor ESC) PWM/AIN/D11
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This permits a single joystick (the right stick in my case) to be used to control the rover:
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elevator = speed control
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aileron = steering
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gear = mode
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flap = learn
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Notes:
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You may (like me) need to reverse the Roll servo, using the Radio Calibration page
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on Mission Planner, else the vehicle will steer in exactly the wrong direction
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when on Auto, but will be OK on Manual.
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GPS notes
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I tested initially with an EM-405A GPS (This is a 5Hz, 5V GPS, and therefore I
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also needed a voltage divider to make the received data compatible with the
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Flymaple 3.3V GPS input on pin D0). This GPS was unsatisfactory due to long
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time lags in changing ground track and speed, and also due to large random
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ground speeds up to 1.0 m/s when stationary. I was able to get ok behaviour
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with very large values for NAVL1_PERIOD of around 40. Don't use this GPS.
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I also tested with a Eagle Tree GPS$v, which is a 10Hz, 3.3V GPS board
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containing a GTPA010 GPS. This GPS worked much better with the suggested
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tuning configuration from
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http://rover.ardupilot.org/wiki/tuning-steering-and-navigation-for-a-rover/
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For the record, the tuning I used with this was:
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CRUISE_SPEED 3 m/s
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CRUISE_THROTTLE 40 %
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NAVL1_DAMPING 0.76
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NAVL1_PERIOD 10
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SPEED2THR_D 0.2
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SPEED2THR_I 0.2
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SPEED2THR_IMAX 4000
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SPEED2THR_P 0.7
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Remaining issues:
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1. Many alignment warnings emitted by the compiler from libraries/GCS_MAVLink
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protocol.h eg:
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/mnt/disk2/src/ardupilot/libraries/GCS_MAVLink/include/mavlink/v1.0/ardupilotmega/../protocol.h: In function 'double _MAV_RETURN_double(const mavlink_message_t*, uint8_t)':
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/mnt/disk2/src/ardupilot/libraries/GCS_MAVLink/include/mavlink/v1.0/ardupilotmega/../protocol.h:274: warning: cast from 'const char*' to 'const double*' increases required alignment of target type
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2. Logging is not implemented.
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