Interference between digital pins?

(4 posts) (3 voices)

ee52bs
Member

Hi,

I am using pins D10 and D11 as the sda and scl lines for a bit banged I2C implementation, and D7 to drive a servo. I have found that when the I2C transmits it is causing pulses on D7 which are being read as a PWM signal and therefore changing the servo angle. Is there any reason why these pins should be interfering with each other? I am using an Olimexino STM-32 rev A.

Thanks,

Ben

Posted 3 years ago #
okie
Administrator

The design looks like it has a lot of overlapping ground return paths, which could be causing signal crosstalk. It may help to increase the size of the pull-up resistors on the I2C bus so that those pins don't draw as much current. If that doesn't help, buffering those pins may do the trick.

Posted 3 years ago #
ala42
Member

Have you configured D7 as output in push/pull mode at all or is it configured at floating input ?

Posted 3 years ago #
ee52bs
Member

D7 is set as a PWM output since it is driving the servos. I will try changing the pull up resistors.

Thanks,

Ben

Posted 3 years ago #

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