Can I run a button ground to LED pad?

KyloDren · November 7, 2023, 6:08pm

My build is going to have a 4pin connector at the top of the chassis, and my button is going to be on the other side of that. The first three pins are going to be +/-/data for the blade strip, the fourth is the button. I don’t have a way to run back to ground on the proffieboard. What happens if I ground the button on the LED - ? This worked great on a ESP8266 setup I had done previously.

As long as the circuit is closed, I think this will work, but I have a feeling those mosfets do not complete the circuit until the button is pressed and ignition happens? So there wont be a way for the button to work because the ground won’t be connected.

Any advice?

profezzorn · November 7, 2023, 11:59pm

You are correct, that won’t work.

However, you can do it the other way around: Hook up the other side of the button to +, and then use the PullDownButton class instead of Button in the config file, and then it will work.

KyloDren · November 8, 2023, 12:09am

thank you! sooo glad I asked. I don’t think its too relevant, but this is a pixel button with six leads on it. LED +, LED -, Data In, Data Out, Switch and “switch common ground”. So I would hook the Switch to LED + (powered directly from battery). And the “switch common ground” to Button 1, but I would change the config from this:

Button PowerButton(BUTTON_POWER, powerButtonPin, "pow");
#endif

to this?

ButtonPullDown PowerButton(BUTTON_POWER, powerButtonPin, "pow");
#endif

profezzorn · November 8, 2023, 12:23am

That seems right to me, but I don’t know exactly what this board is doing, so please take my advice with a grain of salt.

It’s called PullDownButton, not ButtonPullDown:

github.com

profezzorn/ProffieOS/blob/8c433c5a31899bafb9066fcdf169b26f3ef17616/buttons/button.h#L42


      
          
          // For special setups were you want to hook up a momentary button to VCC(3.3V) or Vbat
          // and the other end to the inputs of the Proffieboard / Teensy 
          // 
          // For Proffieboards V2 all inputs can handle Vbat, except for Data4 / blade4pin
          //
          // Usage example, put this in the button config section: 
          // PullDownButton PowerButton(BUTTON_POWER, powerButtonPin, "pow");  
          //
          
          class PullDownButton : public ButtonBase{
          public:
            PullDownButton(enum BUTTON button, int pin, const char* name) : ButtonBase(name, button), pin_(pin) {
              pinMode(pin, INPUT_PULLDOWN);
          #ifdef ENABLE_SNOOZE
              snooze_digital.pinMode(pin, INPUT_PULLDOWN, FALLING);
          #endif
            }
          protected:
            uint8_t pin_;

Other than that you have the syntax right.

KyloDren · November 8, 2023, 1:07am

so appreciated, thank you very much!

Sabersense · November 8, 2023, 8:22am

Oh wow!

So if I’ve understood it right, this basically means you have the option to drive main buttons by shorting the button pad to positive instead of negative! This is a revelation and really good to have in the toolbox. ! I’ve a had a few instances where, like the OP, a shortage of pins has meant I’ve had to go round the houses somewhat to make it work.

This little nugget is pure gold! Looking forward to my next problematic install so I can try it out! LOL!