Questions about Pull-up/Pull-down and PWM

human890209
Posts: 54
Joined: Wed Aug 15, 2018 8:56 am

Questions about Pull-up/Pull-down and PWM

Postby human890209 » Fri Apr 05, 2019 10:08 am

Hi,
I noticed there are pull-ups resistors on the L9110s x2 Motor Drive Module. And lately, I got a tiny L9110s Motor board which doesn't have the pull-ups. And I read the data-sheet of L9110s chips. No pull-ups in the example circuit.
I'm generating the PWM by ledcWrite() and sigmaDeltaWrite() and connect the pins directly to the L9110s' IA and IB.
Q1 Does ESP32's internal pull-up or pull-down resistor is used by ledcWrite() or sigmaDeltaWrite()?
Q2 If not, should I activate any internal resistor by call pinMode(pin, INPUT_PULLUP) or pinMode(pin, INPUT_PULLDOWN) before or after setup the LEDC or SigmaDelta? Will that takes effects or messes the PWM up?
Q3 I've found that when the Frequency is Higher, the power(speed) of the motor is weaker(slower) than when the Frequency is Lower at the same Duty Value. Is a pull-up resistor good for a Higher Frequency situation to speed up the rising of the voltage? Could the interval resistor help?

idahowalker
Posts: 166
Joined: Wed Aug 01, 2018 12:06 pm

Re: Questions about Pull-up/Pull-down and PWM

Postby idahowalker » Fri Apr 05, 2019 11:28 am

I think your idea of using a pull up resistor at the higher frequencies is a sound idea. I'd use external resistors over the internal resistors though. In this case size matters. The resistors in the ESP32 are quite small and tiny and weak in comparison to a 1/8th or 1/4 watt resistor.

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