Sampling time discrepancy between two identical PCA9685 used for Servo controls

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Sampling time discrepancy between two identical PCA9685 used for Servo controls

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michelini
Contributor I

Hello,

checking technical issues in two same control boards that i use, i noticed that the PCA9685 used as a servo controls in one of it, create a sampling time value that is too different from the other one, used for the same application in a different similar control board, creating more than 5% of discrepancy

The first PCA9685 create a sampling time window of 19,4 ms and the second one create a sampling time window of 20,6 ms. 

In the attachment below you can find picture where i highlighted the issue, measuring with the oscilloscope the period generated from both of them, during a general testing manuvre to check the servo behaviour.

 

PCA9685_Sampling_1PCA9685_Sampling_1

PCA9685_Sampling_2PCA9685_Sampling_2

 

Could you please give me an explanation about this recorded event? It is normal having a sampling time window so different (20.6 - 19.4 = 1.2 ms) between two identical PCA9685 that are used for an identical aplication in an identical control board?

Thank you in advance for your support

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guoweisun
NXP TechSupport
NXP TechSupport

There is some error for internal oscillator.

 

 

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