Voltage drop on GPIO pin

[kb2423]

Hi, I am using nRF52832 development board and I have a motor driver. Motor driver has external power supply, I am just using nRF52832 to set directions which consumes low current. P0.11 and P0.12 pins are doing this, when I connect nothing to those pins there is 2.9 V as seen here

When I connect motor driver cables but not connect the motor it can drive led on circuit and voltage goes to 2.19 V

Whenever I connect motor to circuit and try to set one of these pins that pin goes to 0 V.

Finally I tried it with VDD pin. VDD pin can run the motor and it consumes 14 mA

According to this graph sink current is more than 20 mA.  Motor driver consumes less current than max sink current value. What should I do? Thanks in advance. 

[ketiljo]

The GPIO pin can supply some current, but the internal resistance will limit this. The input signal to the motor driver should be high impedance and shouldn't pull the line down like this. Can you provide a schematic and part number for the motor driver?

[kb2423]

This is the schematic, we are using A3918 as motor driver. IN1 and IN2 pins are connected to nRF52832 pins as output with 100 k resistor. Also FL pin is connected to nRF52832 as input.

[ketiljo]

ok, that looks alright. Nothing wrong with the schematic that should explain why the lines are pulled low. I think you must check the pin numbering of the motor driver. Maybe the layout is wrong.

[kb2423]

When I try same pins with STM32 everything works fine, I think pins are correct.

[ketiljo]

It's virtually impossible for a high impedance line to pull down the output like this.