I've just released APMrover2 2.41.

This release fixes a number of bugs in 2.40, plus adds some new features for dual sonar setups. Many thanks to Tom, Greg and Linus for some great suggestions and assistance with this release!

The main changes in this release are:

• switched to new dataflash logging format to improve quality of logs and allow for new log messages without upgrading mission planner
• added SD card logging support on PX4
• fixed compass handling in HIL simulation
• added new INITIAL_MODE option
• changed AUTO_TRIGGER_PIN to be push-on/push-off, so you can run a rover with no transmitter (for Sparkfun competition)
• added SONAR_STOP_PIN and SONAR_SETTLE_TIME options for analog sonars, to allow dual sonar setups with no interference

The most significant changes are for the dual sonar handling. The previous release introduced dual sonar support, but in practices we found that the two sonars would often interfere with each other. Each sonar puts out 40kHz pulses, and if the other sonar receives that pulse then it will register a false obstacle.

The fix is to take advantage of the trigger pins on some sonars (such as MaxBotix sonars). You can set the SONAR_STOP_PIN and SONAR2_STOP_PIN parameters to pins on the APM that will be used to trigger the sonars. You then set the SONAR_SETTLE_TIME for each sonar to the time it will take for the pulse to go out and come back (around 50ms is good for 7m sonars). This ensures that only one sonar is measuring distance at a time, which gives much better results.

Happy driving!