Hello everyone,
I have carried out some experiments on five different STM32 microcontroller devices (STM32F103) measuring the values of the pull-up and pull-down resistances integrated in the GPIO. I have created a voltage divider between VDD and ground using the internal pull-up and pull-down resistors and an external reference resistor. I have found that the value of pull-down resistors are slightly lower in value than the pull-up resistors on all tested devices and their value is less stable than the pull-up resistances.
Anyone knows how the pull-up and pull-down resistors are effectively implemented in the GPIO microcontroller? Are these real resistors with a switch in series or something else? Are the pull-down resistances implemented in the same way as the pull-up resistances?
Thanks.
Marco
