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Generate RC servo PWM signal from CNC controller motor PWM signal
TheSteve:
What processor does your ESC have, you might want to look into flashing it with BLHeli if it is supported which would then allow you to drive the ESC input with the regular PWM(assuming the correct logic levels). You can also convert the PWM to PPM with a "brushless converter". This was done in RC helicopters all the time 5-10 years ago when people wanted to install a brushless ESC but only had the regular PWM motor output to drive the ESC. The converters I used were based on an Atmel tiny13v processor.
Benta:
--- Quote from: Ian.M on January 01, 2020, 01:10:24 am ---Although the classic Futaba servo signal is as you describe, modern high performance servos (and servo input ESCs) commonly accept a faster pulse repetition rate to reduce the response lag.
--- End quote ---
Ah. Thank you for clarifying.
CambridgeMart:
Cheers! After a couple of false starts due to the slightly confusing compilation process for GRBL, I've been able to get a frame length of 16ms with a pulse width of between 1.6 and 2.6ms. I'm in the process of hooking up the ESC to ensure I'm able to initialise it with GRBL.
Regarding the 166ms frame length I mentioned, that comes from the old analogue RC systems that supported 6 or more channels; of course with digital RC gear, the pulse train is generated in the receiver so the frame rate can be higher and support many more channels.
CambridgeMart:
For future reference, I found setting the prescaler to 128 to give a period of just over 2ms worked best, giving me the maximum resolution in pulse width. I can now use about 1/2 of the scale available within grbl or roughly 120 steps in the speed control ramp. I may benefit from rewriting the code in the ESC which is running a 32 bit ARM processor to be able to get a wider control range, but that's for another day.
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