Use 2 Dual Max 14870 with Pi 5 simoultaneously

Support Motor controllers/drivers and motors
1

Hi,
im trying to use 2 “Dual Max 14870 for Pi” motordriver simoultaneously on a pi 5 which is why i dont use them as a Hat but have connected them with cables. I wired DIR and PWM to a GPIO and PWM port of the pi 5. Aditionally I connect a ground cable between the Pi and the motordriver. I run the Motors of a battery and the Pi with the Official Pi-Powersupply.
As of now i managed to get both motors (Pololu 20D 12V) working but have the problem that pulling the DIR pin HIGH(changing direction) sometimes results in the Motors stopping until i pull the DIR pin low again. This happens quite randomly and i couldn’t find a pattern except it only happening when i pull the DIR pin to high, never when pulling to LOW. Strangely the motors only seem to stop when changing direction. Writing DIR continously to HIGH works just fine.
I couldn’t find any difference when changing the frequency of the PWM signal or reducing the Duty-cycle. As the motors stop spinning completly I thought that there was an Issue with the PWM signal but I checked it with an Oscilloscope and it looks fine, no matter the state of the DIR pin.

Can this be a problem because i am using 2 different power sources, because i havent connected enough/have connected to many pins to the motordriver or something else?

2

It should be fine to use two separate power sources as long as they are capable of handling the loads. What are you using for your motor power source?

I recommend checking your ground connection since the behavior your described is typical of a missing or bad ground.

You mention “pulling” the DIR pin high or low several times; could you clarify if you are actually using pull-up/pull-down resistors (either internal or external) or if you are driving the pins high/low directly?

Also, could you post the simplest complete code that demonstrates the issue as well as some pictures of your setup that show all of your connections?

Brandon