VexCode IQ Blocks problems with drive train and gyro


I configured the drivetrain with a gyro sensor. When I have the drivetrain configured with the arrow pointing up, the gyro works fine, but the robot drives backwards when I program it to drive forward.

I configured the drive train with the arrow pointed down as I have in the screenshot. But when I do this, I have a problem and the robot just turns continuously when I just ask it to turn right for 90 degrees.

Anybody else encounter this problem and find a solution?


Check if your left and right motors are swapped…

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you are totally right. Thanks!

I’m having the same issue in VEXCode IQ Blocks and drivetrain arrow pointed down (same as OP): with no gyro, drivetrain turns 90 degrees and stops. With a gyro, it spins endlessly (and the wrong direction).

If I select the other direction for the drivetrain (arrow up), it executes correctly, both direction and turn radius. Likewise, if I disable the gyro, it executes correctly regardless of drivetrain direction. I have confirmed that I have the proper motor configuration and I’ve used this same config for multiple successful programs.

When started
set turn velocity to 10%
turn [right] for 90 degrees
stop driving

Sure seems like a gyro handling bug? Thanks in advance for any help.

typically this is because left and right motors are swapped. However, give us your exact robot configuration and we can have a look. Any gears between motors and wheels ?

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Thanks-- default Clawbot build. No gearing involved. Left motor in 1, right in 6 (gyro in 4).

I figured out what I was doing wrong: posting here for anyone else who gets in this situation. The issue is which direction the drivetrain arrow is pointing. I was misinterpreting the graphic in the drivetrain setup: I was reading that graphic as asking which side of the robot the brain was mounted onto (in my case, brain on the back, direction of travel should be the opposite direction, so I chose the down arrow). The graphic is really looking just at which way the brain is oriented. The bottom part with the little tab sticking out is supposed to represent where the “VEX IQ” label is printed on the brain, I guess?

Long story->short: ignore the robot shape in that graphic. Up arrow means you travel in the direction of the top of the brain. Down arrow means you travel in the direction of the bottom of the brain.

yea, the graphic has (as far as I know anyway, I didn’t design that graphic) anything to do with robot or brain orientation. process should be something like this.

decide which is the front of the robot, set the ports for motors on left and right based on this physical orientation. Do a quick test and see if the robot moves forwards when using the drive.forward block. If the robot moves backwards then select the alternate arrow in the drivetrain config. The issue is that the software does not know how motors are connected to the wheels, motors may be directly connected or they may use gearing to increase speed or just allows motors to be mounted in a more convenient location. Once the robot drives forwards and left and right are configured for the correct ports, everything else should fall into place and the robot should make correct turns.


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