Query on RC Trim & Deadzone

ArduCopter
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1

Hi Everyone,
Currently, I am using a RC transmitter and testing on how applying trim & deadzone modifies the raw channel data from rc transmitter. I am having a query on how this works.

  1. Suppose for a channel I get min pwm value is 1000 when I push the stick to extreme left, max pwm value is 2000 when I push the stick to extreme right and center stick value is 1500.If for a certain stick movement, I get pwm value of 1530 before applying deadzone. Now after applying the deadzone of 20 on that channel, should I get 1530 (since it is outside the range of 1520 and 1480) or 1530 - 20 = 1510 for the same amount of stick movement as before?
  2. Suppose I add a trim of 1600, now will the extreme left position give me 1000 or 1100 (since shift from previous mid/neutral point is 1600 - 1500 = 100)?
  3. For throttle channel should I make all the trim related calculation with respect to lower throttle stick value (1000 and not 1500 unlike before) when using trim since that is the neutral point for throttle channel?

Can someone having previous experience on using Trim & Deadzone please help me with this?

Thanks,
Sayan

2

https://ardupilot.org/copter/docs/common-radio-control-calibration.html

RCx_MIN/MAX are the values the FC sees when you fully deflect a stick. So if you push the Roll stick fully right and the RC link sends a signal of 2011, if RC1_MAX is also at 2011 the FC will know you are demanding 100% roll right.

RCx_TRIM is middle position. When you let go of the stick what signal is RC link sending to the FC. It will usually be around 1500. This way when you let go of the stick the FC knows you want level attitude or stopped.

Deadzone is how much movement around the trim is allowed before the FC starts reacting to the input. Some radios will “wander” a bit around the middle point and this stops unwanted comands. So if you have a deadzone of 10, and trim of 1500, the stick would need to move 1490 or 1510 before it starts to do anything.

Defaults for the dead zone are usually good, I very rarely change them.

The RC calibration linked above will set Min/Max/Trim.

3

Thanks for your answer Allister! But I have previously gone through the documentation and know the theory of trim and deadzone. What I want to know is what it’s effect will be (in numbers as asked in the question) on the raw pwm data.

4

Trim and deadzone don’t change any of the raw data. You could set the trim where ever you want, it doesn’t effect the end points. But don’t change the trim, leave it at the neutral point of the sticks.

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5

Actually, I am using FS-i6 transmitter where, if set the trim using the trim buttons and then match the extreme left position of the stick, I see that there is a shift of the same value as of the trim. So, if trim is 1600 for raw channel, then the neutral point is shifted by 100 (1600 - 1500). This causes the left extreme position to output the pwm value of 1100.

6

If you change the trim on your transmitter you shift transmitters output.
And this you will see on FC RC input. But it has nothing to do with the settings of the FC.
If you want that your FC works in all modes as expected, than it is best to not use any trims on your transmitter and if you changed the trim of your transmitter for any obsure reason you need to recalibrate the RC-System on FC side and than leave FC the FC trims unchanged forever.
Again best is don’t to use any trim on RC-transmitters

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7

@Juergen-Fahlbusch beat me to it. Do not use any trims on the RC. If you can turn them off that’s the best so you don’t have to worry about issues in the future.

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