Swerve questions (Languages, CAN)

[Ether]

Originally Posted by Jared

Your encoder will need to be used with the FPGA or with interrupts in order for it to work properly. Your user code which runs on the CPU would need to run impractically fast to decode the encoder PWM.

You have a few options to try to decode this signal

You can do what Ether recommended, and try to use interrupts. This is likely more difficult than it sounds to get everything working properly. Also, interrupts and less commonly used features are likely the last priority of the roboRIO development team and beta testers, so you may encounter strange, hard to diagnose issues with interrupts.

You could also attempt to read the encoder on a separate device, like an arduino or basic stamp. There are likely software libraries that exist for reading an encoder like this already. If not, you could likely write your own using the "pulseIn()" function on the arduino. You can connect the arduino to the roboRIO through a serial connection very easily.

Hi Jared,

Good suggestion. The arduino (or other microcontroller) could certainly decode the PWM pulse width. (Complexity and cost should be factored into any final decision.)

Decoding PWM duty cycle (which is the datasheet-recommended way to decode the PWM signal for the MA3) would require measuring both the pulse width and the period (or the associated non-pulse width) for the same cycle. I don't think the 2014 FPGA is programmed to do that.

FTR, I wasn't recommending using interrupts (on the RIO). I was trying to discourage that idea.

[bharrison6]

we haven't got the encoders in yet perhaps we will just get the analog encoder instead which should reduce complexity significantly. thanks for all the responses I'll give you an update once we get the encoders In and get this thing running. we are currently making a wooden prototype Of our new pod as we speak

Thanks Bryant