Thread: ANNOUNCING: navX MXP Robotics Navigation Sensor
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Unread 05-03-2015, 03:09
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Re: ANNOUNCING: navX MXP Robotics Navigation Sensor
Quote:
Originally Posted by Thad House View Post
We did notice that rebooting the robot code only fixed the issue a few times. Most times it actually did not fix the issues, and the gyro still wouldn't return anything. Even resetting the gyro, then resetting the robot code did not help.
We are now able to repeatedly reproduce a condition in the lab when there's a RoboRio Stage 2 brownout for ~30ms (shorter than that, or longer than that does not cause the problem). In this condition, the Invensense chip on the navx MXP gets reset, but the navX MXP microcontroller doesn't - and at that point, the sensor no longer returns gyro values. This condition affects I2C, SPI and TTL UART. This condition doesn't occur for shorter brownout periods (since the navX MXP onboard capacitor provides enough capacity to ride it over). And it doesn't occur for longer brownout periods (since the navX MXP microcontroller gets reset). Your info about 20ms brownouts provided the clue needed to find this.

When this case occurs, the S1 and S2 LEDs on the navX MXP will not be lit, even though the red 3.3V LED will be lit. This is the tell-tale sign.

Once this happens, the navX MXP microcontroller needs to be reset - by pressing the navX MXP reset button, or rebooting the RoboRio.

This should be fixable via a navX MXP firmware update, we should have something in a week or so (the team is traveling to Central Valley Regional this weekend).

In our testing, this case does NOT occur when a secondary 5VDC power source is provided to the navX MXP via the USB connector, since in this case all circuitry onboard the navX MXP stays completely powered through the brownout event.

Based upon this, we reiterate the recommendation to provide a backup power source (via USB connection to the VRM) if Stage 2 brownouts are expected, and will also update this thread once a firmware update is available.

[Please note this does NOT appear related to the errors reported by a few teams during Week 1 events when connected to the FMS. Until we have more information the recommendation is, as previously stated by Alan Anderson, to restart the robot code immediately after first connecting to the robot on the field.]
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