Adding files which enable a simulation with the autonomous underwater
vehicle (AUV) from the Technical University Hamburg-Harburg

inverted S.bus signal and fetch the data of each channel and publish it

2. Fix the bug of linux_pwm_out, when the protocol is pca9685,
after the init method is executed,the method of determining the return
value of init method is incorrect,this will cause the driver to fail

3. Add linux_sbus driver to other posix prefixes cmake files

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

There are bugs in version 2.05.1 (default version in Ubuntu 16.04)

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

All others are initialized this way.

   This is a back port of upstream NuttX PX4 contrib of

   ef42c25 stm32f7:SDMMC add dcache alignment check in dma{recv|send}setup
                   In the where CONFIG_SDIO_PREFLIGHT is not used and dcache
                   write-buffed mode is used (not write-through) buffer alignment
                   is required for DMA transfers because a) arch_invalidate_dcache
                   could lose buffered writes data and b) arch_flush_dcache could
                   corrupt adjacent memory if the buffer and the bufflen, are not on
                   ARMV7M_DCACHE_LINESIZE boundaries.

   1e7ddfe  stm32f7:SDMMC remove widebus limitation on DMA
                    There is no documantation for the STM32F7 that limits DMA on
                    1 bit vrs 4 bit mode.

   dffab2f  stm32f7:DMA add dcache alignment check in stm32_dmacapable
                    In the case dcache write-buffed mode is used (not write-through)
                    buffer alignment is required for DMA transfers because
                    a) arch_invalidate_dcache could lose buffered writes data and
                    b) arch_flush_dcache could corrupt adjacent memory if the
                    maddr and the mend+1, the next next address are not on
                    ARMV7M_DCACHE_LINESIZE boundaries.

   38cbf1f  stm32f7:DMA correct comments and document stm32_dmacapable
            Updated comment to proper refernce manual for STM32F7 not STM32F4.
            Added stm32_dmacapable input paramaters documentation.

The code was violating the rule 'every successfull poll must be followed
by an orb_copy'.
The result was a busy loop.

 - change a little bit to make the code more readable

This is needed when logger is logging to file and ulog streaming gets
activated.

hardfault_store_filename() opens and closes a file descriptor, so if we do
it before opening the log file, we need one file descriptor less

This reduces the maximum number of needed file descriptors by 1 when using
ulog streaming.

This improves the printfs which will be logged. This should improve to
debug the camera triggering. The debug printfs are disabled by default.