(credit to Mitch Miers <mmiers@mmiers.com>):
setup() is attempting to initialize the hardware, and while doing so
is attempting to output some text via the console (and maybe mavlink
data). The problem is, the output isn't going to complete once a
write buffer is full, because LinuxUARTDriver::_timer_tick() doesn't
perform work until _initialized is true. So, what happens is,
setup() (and subroutines) call LinuxUARTDriver::_write(uint8_t c),
which loops waiting for buffer space to become available (once the
write buffer is full). The buffer never gets space, because the
UART thread is waiting for initialization to complete before it
will write out data and drain the buffer, but that doesn't happen
until setup() returns (see AP_HAL_Linux_main.h).
Refer to https://groups.google.com/forum/#!topic/beaglepilot/dQlxse11JNI
The MPU9150 is a 9 axis sensor that includes 3 accelerometers,
3 gyroscopes and 3 magnetometers. All accessible through I2C.
The AP_InertialSensor_MPU9150 class allows APM to use this sensor.
This only works for the centralised builder, the modified Arduino IDE
will still include the NMEA and SIRF drivers meaning it will require
approximately 4k additional flash which may push us over the limit on
the APM2. Users will instead need to exclude other features to get
below the APM1/2 flash limit.
Previously we were setting to non-block after arming but this reduce the
chance of bumping into a NuttX USB driver issue that can cause the uart
to become unresponsive and also makes Copter consistent with Plane
The compass.configured() method checks the eeprom and cannot be const
meaning the Arming object requires a non-const reference to the compass.
Removed check for null compass because the compass object is always
created although this could lead to unnecessary pre-arn check failures
even though compass-use is set to false.
This checks that when compass offset learning is off, that the offsets
are non-zero and that the detected device id matches the device id
stored to eeprom when the offsets were last saved.
