I am trying to set up a function for turning. It takes an int input for which direction to turn, sets up the synched motors for the correct direction, and then runs the motor to turn.

When I step through the program it fails with the switch line highlighted and gives the following:

Byte Code Interpreter Exception:
Program Slot: 0. Task ID: main[0]
Error at PC: Sub: turn+0x0008
Task PC: Sub: turn+0x0008.
TaskState: 'Exception'
Exception Type: 'Cannot Update Slave Sync(60)'

The code for the turn function is:

// Turns the robot, Case 0 is for left turn, Case 1 is for right turn
void turn(int dir)
{

// Set motorencoders to zero to measure out a 90 degree turn
nMotorEncoder[motorB] = 0;
nMotorEncoder[motorC] = 0;

switch (dir)
{
// Left Turn
case 0:
if (nSyncedMotors != synchBC)
nSyncedMotors = synchBC;
if (nSyncedTurnRatio != -100)
nSyncedTurnRatio = -100;
motor[motorB] = TURNSPEED;

// Right turn.
case 1:
if (nSyncedMotors != synchCB)
nSyncedMotors = synchCB;
if (nSyncedTurnRatio != -100)
nSyncedTurnRatio = -100;
motor[motorC] = TURNSPEED;
}
}

I set up the if statements because the robot would crash if it was given the same nSyncedMotors command twice in a row. TURNSPEED is a #define constant.

I'm afraid you can't reset the encoders of the slave motor Remove the nMotorEncoder[motorC] = 0; and it'll work fine. Is there a reason you need to reset the encoders all the time?

- Xander

that was a remnant of my original version where I was telling it to make 90 degree turns

Thanks for the help. It works now.