Gyro PID User drive - How we did it

[Alan Anderson]

Originally Posted by tdlrali

Hey Alan, is 254 really the max in the IFI setup?

The proper maximum pwm output is indeed 254. Here is one bit of documentation to that effect:

Originally Posted by IFI Tech Support

In the Robot Controller program, a value of 0 corresponds to a 1ms pulse. A 1.5ms pulse means neutral, or a value of 127, while a 254 corresponds to a 2ms pulse.

See also this post on the IFI Technical Support forum, which shows the range 231-254 as "Full Forward" on a Victor.

Originally Posted by Bongle

255 can do some wierd stuff. Way back in 2003, I couldn't figure out why our robot wouldn't drive straight. Another team pointed out that 255 was some sort of null character. I changed it to 254, and the thing started driving perfectly.

The communication protocol between OI and RC uses a pair of 255 (0xFF) characters to synchronize frames of data. Back in the pre-C days, it might have been possible to confuse it by setting adjacent pwm values to 255. My experience is with the 2004 and later control system, which refuses to report a pwm value greater than 254. I don't know whether the limit is enforced on the actual pwm output or if it's just the dashboard data coming back from the RC that won't go that high.