Is there any way to increase the reaction speed of the Pololu Jrk 12v12 Motor Controller when using it in RC mode?
The data sheet says that it will ‘accept pulses from 400 to 2600 μs at a frequency between 10 and 150 Hz’ but many RC systems are capable of refresh rates of 250Hz, 333Hz and even 560Hz (with reduced pulse width).
The system I am building is gyro-stabilised and for the smoothest operation i need the highest refresh rate possible, my gyros can give a signal at up to 560Hz but because the highest standard rate the Jrk can receive is only 77Hz (the next standard rate being 250Hz and out of range) my system vibrates at 77Hz and is not smooth.
Is there a possibility to increase the input rate via a firmware update or any other way (using RC input mode) to increase the responsiveness of the system?
I have made a small modification to the Jrk firmware for you that removes the requirement that the RC pulse input line (RX) go low for at least 2.8 ms between pulses. This means that the jrk’s RC mode will be more susceptible to noise, but it does allow the jrk to process higher-frequency RC signals. You can get the new firmware and try it here:
I tested the RC input of this firmware at 333 Hz using our Mini Maestro 12-Channel USB Servo Controller. It will probably also work at 560 Hz, but I have not tested it at that frequency, and the minimum pulse width of 400 microseconds still applies. What range of pulse widths does your Gyro produce at 500 Hz?
Please be aware that I did not test all the features of the jrk with this firmware. It is quite possible that some features will not work properly, so please look out for anything that changes when you apply this firmware modification and let us know if you have any problems.
Also, be sure to set your PID period to something smaller than 10 ms.
Your project sounds interesting! Let us know how it goes!
David thank you so much, that is really kind of you and you’ve done it so quickly as well!
333Hz will probably be fast enough, when outputting at 560Hz the pulse width centres at 720uS (as opposed to 1520uS in standard systems) so it does go below 400uS at the low end (~200uS min, 1300uS max) - however the change you’ve made will allow me to update the system 4 times more frequently and should give a huge improvement in performance
I will be sure to let you know how the project goes.
