FEZCobraIII/G120 set pin states low during boot?

NETMF & Gadgeteer
1

Hi,

when the Cobra boots up after power on/reset, all pins seem to be set active/high, until my application is loaded and i set them low.

This is a (big) problem, since we have a lot of components/relays in circuit, which must not be triggered, if the device starts.

i found several old similar questions, where the statement is “its by design”:
https://www.ghielectronics.com/community/forum/topic?id=6806&page=1
https://www.ghielectronics.com/community/forum/topic?id=15399

Did something changed in this design? Is it possible to configure the g120 to let the pins be low until boot by now?

Furthermore what is the reason to set pins to high if the device/controller starts? It should be the applications/developers response to set the pins to high, if he want’s to. Powering on everything during boot up means there is no control over what is happening during boot time.

Thanks in advance.

Daniel

2

This is normal. You’ll have to use pull down resistors on all pins that you are expecting to be low.

1 Like
3

Hi Daniel

If you need to guarantee the state of a pin at startup (or restart, or any state where your app may have not got full control) you must do that with hardware - pull up/down resistors in most cases.

1 Like
4

This is normal with almost all microcontrollers as the GPIO is normally set to input with weak pullups. As others have said, you need to put pull down on the IO you want in a low state during the power up time until your code is running.