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PPM read has an offset

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Last seen: 4 years 4 months ago
Joined: 2018-09-11 11:53
Posts: 12
PPM read has an offset

I'm generating PWM from ARDUINO, it works very well, I tested it with other ESC and servo and I checked with oscilloscope.

When I enable the RT APP button to see the PPM read by the VESC, it always has an offset of +0.2 ms. For example if the PWM is 1ms, the app shows me 1.2ms. Where is this offset coming from?

Is it a problem that I'm generating PWM for PPM? Actually is the input a PWM or a PPM? I don't get why PPM would make any sense...

Last seen: 3 years 6 months ago
Joined: 2019-05-20 18:22
Posts: 2

I experience this too. Tried Arduino Uno and Teensy LC. Verified on an oscilliscope. It's on the latest VESC tool as of May 24,2019. 


This has been causing issues during calibration and prevents the motor from starting sometimes. 

Stupidspencer's picture
Last seen: 1 year 10 months ago
Joined: 2019-06-20 00:06
Posts: 32

I have this issue as well, although I haven't done any testing like OP has. When I run the PPM calibration (through VESC tool for Android v1.15) everything looks good and the graphic bar moves consistently with the commanded throttle from 0 to full. But after the calibration wizard is complete, the motor won't respond until I get to (what should be) about 1/2 throttle. I am able to get around it in my transmitter settings, but not very well. I can't change the channel endpoints enough, so I have to change the exponential adjustment a lot.  I end up with the motor starting to spin just as I start pulling the trigger, but the acceleration is very slow in the low range, and very aggressive (and hard to control) as I get to full throttle.

Here are the specifics:

Radio is a Turnigy GTX3 with receiver connected through PPM to VESC 6.6

I run PPM calibration with all settings default

To get motor response over entire throw of throttle trigger, I change the following transmitter settings:

Forward endpoint: 80% (default 100%)

Reverse endpoint: 85% (default 100%)

Exponential: -15% (default 0%)

Dual rate: 35% (default 100%)

Trim: 0% (default value)


I've tried playing with it quite a bit, and these settings are the only way I can seem to get response over the entire throw of the throttle trigger. I think this must be VESC tool bug.