Sampling time discrepancy between two identical PCA9685 used for Servo controls

michelini — Fri, 28 Jul 2023 10:09:57 GMT

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_1

PCA9685_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

Re: Sampling time discrepancy between two identical PCA9685 used for Servo controls

guoweisun — Mon, 31 Jul 2023 05:47:25 GMT

There is some error for internal oscillator.

topic Re: Sampling time discrepancy between two identical PCA9685 used for Servo controls in Other NXP Products

Sampling time discrepancy between two identical PCA9685 used for Servo controls

Re: Sampling time discrepancy between two identical PCA9685 used for Servo controls