There is also the newer Ardupilot Mega, which has an IMU shield that is nicknamed the Oilpan (http://store.diydrones.com/product_p/br-0012-01.htm). It does not have any firmware or processor itself, but is simply a sensor board that uses the APM board's processor.
All firmware can be updated any time you want. For the older ArduIMU, you need to use Arduino. For APM, the Mission Planner will check for new firmware and load it when you launch it, no Arduino required.
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There is also the newer Ardupilot Mega, which has an IMU shield that is nicknamed the Oilpan (http://store.diydrones.com/product_p/br-0012-01.htm). It does not have any firmware or processor itself, but is simply a sensor board that uses the APM board's processor.
All firmware can be updated any time you want. For the older ArduIMU, you need to use Arduino. For APM, the Mission Planner will check for new firmware and load it when you launch it, no Arduino required.