TRIG_X Signal with the STEVAL-PTOOL4A

[AnthonyK]

Hello,

I am reading the documentation of the STEVAL-PTOOL4A, I have noticed that it is equipped with a TRIG_X  to enable/disable the DC/DC booster. I don't know if I understood well its functionality, but It will mainly turn on/off all the board including the MCU. So each time, we trigger, the MCU will execute from the reset_handler right? But maybe I want to keep the MCU on always, and I want to scan an input and when it is On, it will turn on or off the motor depending on its status. How it could be done by TRIG_X? Or I should use in this case another GPIO and I configure it manually? For example could I use the one of the potentiometer instead?

Thank you

[Peter BENSCH]

In the original state of the STEVAL-PTOOL4A (R82 is fitted), U5 (L6981, incidentally not a booster but a buck regulator) is permanently switched on and TRIG_X has no effect because EN_BUCK is connected to VBATT+.

The DC_DC latch can only work if you remove R82 because EN_BUCK is then controlled by TRIG_X via Q7. When SW1 is pressed or TRIG_X = Low, EN_BUCK is activated, which switches on the buck regulator and thus the entire board. The function of the latch is also described in UM3374, section 5.5.9.

Hope that helps?

Regards
/Peter

[AnthonyK]

Hello Peter,

Yes that's what I have understood also. It is like a power button. 

Thank you for your help.

[Peter BENSCH · Accepted solution]

It's like a power button if R82 is removed. Otherwise it doesn't do anything.