Prevent short circuits in BM without diodes

Author: afpineda

doc/changelog.md

@@ -1,5 +1,14 @@
 # Change log
 
+## 7.1.2
+
+- Button matrices configured for negative logic,
+  now use open drain mode for the selector pins.
+  This prevents a short circuit when the diodes are removed
+  which is unfortunately a common use case among users.
+  Note that **short circuits cannot be avoided** in a button matrix
+  without diodes configured for positive logic.
+
 ## 7.1.1
 
 - The code for active wait has been revised for even better accuracy.

doc/hardware/subsystems/Switches/Switches_en.md

@@ -43,6 +43,10 @@ You should be able to extrapolate those designs to your needs.
 Button matrices in this project work in *positive logic*
 (inputs are internally pulled down).
 
+> [!CAUTION]
+> Do not remove the diodes from these designs.
+> Otherwise this firmware will cause a **short circuit**.
+
 ### Button Matrix (25 inputs)
 
 Needed parts (not counting input hardware like push buttons nor a perfboard):
@@ -77,7 +81,7 @@ This [circuit design](./BtnMatrix16Inputs.diy) requires no wiring but takes more
 
 The purpose of this circuit is to transform analog potentiometers
 into "on/off" switches that can be wired to a button matrix.
-**Usefull for clutch paddles if no ADC-capable pins are available**.
+**Useful for clutch paddles if no ADC-capable pins are available**.
 Another soldered potentiometer (called "trimmer")
 will calibrate the position where on/off switching happens.
 Please, **follow this calibration procedure in order to minimize battery drainage**:
@@ -407,6 +411,13 @@ Selector pins must be wired to valid output capable GPIO pins.
    Such a hardware design is not in this project,
    but this option allows you to use a recycled button matrix from another project.
 
+> [!CAUTION]
+> If, despite my advice, your button matrix does not have diodes,
+> configure your custom firmware to work with negative logic
+> by setting the second parameter to `true`.
+> Otherwise, you will have a **short circuit**.
+> Either way, you will have ghost inputs.
+
 For example:
 
 ```c++

src/common/InputHardware.cpp

@@ -277,7 +277,7 @@ ButtonMatrixInput::ButtonMatrixInput(
     // Compute mask and initialize GPIO pins
     for (auto row : this->matrix)
     {
-        internals::hal::gpio::forOutput(row.first, negativeLogic, false);
+        internals::hal::gpio::forOutput(row.first, negativeLogic, negativeLogic);
         for (auto col : row.second)
         {
             internals::hal::gpio::forInput(col.first, !negativeLogic, negativeLogic);