[FTC]: Possible issues with lost messages to DC Controller.

[PhilBot]

Hi

I think anyone who's done FTC for a year or so knows that the occasional message from the NXT to/from the DC Motor controllers gets corrupted.

This has caused all sorts of Autonomous problems in the past (some of which have been corrected with the current code).

However, I think I've discovered a new wrinkle.

The code that's generated by the LabVIEW For LEGO Mindstorms (LVLM) software for the new templates is clever in that it doesn't send mechanisim commands continously (as with prior code), instead it detects when buttons are pushed or released and generates code that is called when either of these events occur.

So if you are using two buttons to raise or lower a mechanism (like a scissor lift) the code sends a motor move command when you press the button, and a motor stop command when you release it (and nothing the rest of the time). This is very efficient as it cuts down on I2C communications with the Motor Controller.

However, there is a problem. If the comms glitches when you are sending a start or stop command, the action is lost, so the controller continues as if you didn't press or release the button. So in my case, if you are tapping the button to raise the lift in tiny increments (eg for testing), every now and then the stop command gets lost and the lift keeps moving. OWE!!!

This is especially bad if you don't notice at the end of a motion and the motor keeps on running against the stops. (Blue Smoke time).

So far it's only happened a few times, but it's enough for me to consider going back to the old style of issuing motor commands each time around the loop. That way a missed command gets resent 20ms later.

Anyone else seen this behavior on a mechanism (not drive train)?

Phil.