NAVX vs. Spartan board

[Andrew_L]

Originally Posted by slibert

the Spartan requires mounting perpendicular to the robot chassis (parallel to the Z-axis plane)

[Citation needed]

[thatprogrammer]

Originally Posted by slibert

Hmm, perhaps that's also worth putting in the side-by-side comparison Ahad put together - the Spartan requires mounting perpendicular to the robot chassis (parallel to the Z-axis plane), whereas the navX-MXP can be mounted in any of 8 possible orientations. That ends up impacting RoboRIO mounting since both use the RoboRIO MXP port. The navX-MICRO - which doesn't use the MXP port - can be mounted independent of the RoboRIO.

Scott, thanks for the suggestion! I made an edit to the list to add in your points.

[Jared Russell]

Both of them have been used successfully by many teams, and you can't go wrong using either for helping determine your robot's heading.

Honestly it is really hard to judge a gyro by its spec sheet - you always end up with apples vs. oranges (ex. the ADXRS has *excellent* tilt and vibration rejection specs, whereas the MPU-9250 can use its linear accelerometers for tilt rejection), and various manufacturers may be more or less conservative about the relationship between their specs and their actual median product performance.

When it comes to pure yaw performance, I'm a bit surprised that nobody has done a benchmark yet (Put both gyros on the same robot, calibrate right before starting, drive around for 2 minutes, return and manually align the robot to exactly the same angle...repeat for N trials). I'd be shocked if there was a significant difference, to be honest.

Of course, there's no doubt that NAVX wins hands down in pitch, roll, linear acceleration, and direction of gravity measurement though.

[slibert]

Originally Posted by Andrew_L

[Citation needed]

Per the ADXRS453 datasheet, the Gyro on the gyro-enabled version of the Spartan board is single-axis, and is the SOIC_CAV package designed for yaw rate sensing. I haven't come across any Spartan board mounting instructions, but if we thus assume the purpose of the ADXRS453 is to be a yaw rate sensor, then any mounting configuration in which the sensor is not parallel to the FRC field surface will result in integrated yaw angles which include an error proportional to the offset angle from parallel. For instance, if the board is mounted vertically, the sensor would be measuring a "tip" or "tilt" angular rate rather than yaw. This is as compared to a triaxial gyro which can measure yaw rate even when mounted vertically.

If you think this is incorrect, please let me know.

[euhlmann]

I'll put in that we had no issues with NavX heading getting off due to defenses. During our autonomous, our robot was able to reliably and precisely get itself to the tower (using the NavX and encoders on a tank drive for dead reckoning), even after slamming down over the rock wall.

[AustinSchuh]

Originally Posted by slibert

Per the ADXRS453 datasheet, the Gyro on the gyro-enabled version of the Spartan board is single-axis, and is the SOIC_CAV package designed for yaw rate sensing. I haven't come across any Spartan board mounting instructions, but if we thus assume the purpose of the ADXRS453 is to be a yaw rate sensor, then any mounting configuration in which the sensor is not parallel to the FRC field surface will result in integrated yaw angles which include an error proportional to the offset angle from parallel. For instance, if the board is mounted vertically, the sensor would be measuring a "tip" or "tilt" angular rate rather than yaw. This is as compared to a triaxial gyro which can measure yaw rate even when mounted vertically.

If you think this is incorrect, please let me know.

That is correct. The roboRIO needs to be horizontal.

We developed the Spartan Board mostly to solve brownouts and latching connectors. If it hadn't been for the brownout problems with the roboRIO, we would have likely developed the board only for 971 and not bothered to sell it. The regulators brown out right about when the roboRIO CPU browns out.

We've been using the ADXRS453 for a number of years, and have been impressed with it. Once you are making a board with a bunch of active circuitry, adding a gyro is easy. I might have picked a different gyro if I were to start over today.

One of the main drivers for selling the board was because there was enough interest from our friends in the board that we couldn't continue to fabricate enough of them each season. By selling it, we were also able to get it approved by FIRST, and add PWM pass-throughs. Selling the board has honestly been a lot of work... RC and WCP have been a huge part of figuring out how to build the boards in quantity and to sell them.

[Andrew_L]

Originally Posted by slibert

Per the ADXRS453 datasheet, the Gyro on the gyro-enabled version of the Spartan board is single-axis, and is the SOIC_CAV package designed for yaw rate sensing. I haven't come across any Spartan board mounting instructions, but if we thus assume the purpose of the ADXRS453 is to be a yaw rate sensor, then any mounting configuration in which the sensor is not parallel to the FRC field surface will result in integrated yaw angles which include an error proportional to the offset angle from parallel. For instance, if the board is mounted vertically, the sensor would be measuring a "tip" or "tilt" angular rate rather than yaw. This is as compared to a triaxial gyro which can measure yaw rate even when mounted vertically.

If you think this is incorrect, please let me know.

My apologies, I was assuming you meant to say either of the Spartan Boards could not physically be mounted in other planes. I didn't want teams getting the wrong idea that they couldn't mount a Spartan Board without gyro any direction other than parallel with the floor.

[MichaelBick]

Originally Posted by slibert

That ends up impacting RoboRIO mounting since both use the RoboRIO MXP port. The navX-MICRO - which doesn't use the MXP port - can be mounted independent of the RoboRIO.

The navX-MXP can also be mounted independently, assuming you use USB to connect to the roboRio

[bretcobrageek]

Thanks everyone for the great comparisons and feedback. As I suspected, both boards are great at the basics but do have some differences which may make a difference depending on what you want to do or how you want to use their capabilities. The idea of the base spartan board with the Navxmicro is really intriguing. I'll consult the rest of the team and see where we want to go for this season.