A pulled down Pin , later should have a HIGH

Hello there

I have a problem with floating pins. I need a LOW on an "Enable" pin right from the start, so I place a PULLDOWN resistor between my "Enable" pin and GND.

Later I need a HIGH on the "Enable" pin. Is that possible?

Backstory:
I want to control a stepper motor using a stepper driver. The stepper driver "step" pin is floating when powering on the Arduino and the motor start to vibrate for about one second. And I dont want it to do that.
The stepper driver has an "enable" pin that need to be HIGH to make the steppers work. So I want to have a LOW on the "enable" pin right from the start and maybe 2 seconds later have a HIGH.

Thanks in advance for your answers

Best,
Anxodia

If I have understood you correctly then the usual way to hold a pin low at startup is to put a capacitor between the pin and 0V and a resistor between the pin and Vcc. At power up the capacitor will be discharged and will hold the pin low. After a short delay the resistor will pull it high.

Capacitor value maybe 1μF, resistor maybe 100k, but the values depend on how long you need to hold the pin low.

Thank you for the quick reply. I will try this. I hope I have a capacitor laying around. :slight_smile:

If anyone has another idea/approach please let me know!

I could think of one or two, but I'd start with the solution or an RC network as @PerryBebbington suggested since it's simple and usually very reliable.

I have not currently any capacitors around.

A with resistor pulled down Output can not be set to HIGH state afterwards via code?

Then I could pulldown the EN pin to GND with a 10k or 4,7kOhm and after the arduino has booted I could set a digitalWrite(enable, HIGH) on that pin? That doesnt work?

Yes, a pulled-down output can be driven HIGH. I'd use a 10k for that, for minimal current flow.

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It works! THX!

12kOhm resistor between my Digital IO pin from arduino and GND. And then wired from the same pin to the EN pin on the driver.

Best,
Anxodia

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