add SPLIT_HAND_MATRIX_GRID support (#8685)

Co-authored-by: Danny <nooges@users.noreply.github.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/docs/feature_split_keyboard.md b/docs/feature_split_keyboard.md
index 63374a804..ce470b996 100644
--- a/docs/feature_split_keyboard.md
+++ b/docs/feature_split_keyboard.md
@@ -90,6 +90,24 @@ You can configure the firmware to read a pin on the controller to determine hand
 
 This will read the specified pin. If it's high, then the controller assumes it is the left hand, and if it's low, it's assumed to be the right side. 
 
+#### Handedness by Matrix Pin
+
+You can configure the firmware to read key matrix pins on the controller to determine handedness.  To do this, add the following to your `config.h` file:
+
+```c
+#define SPLIT_HAND_MATRIX_GRID D0, F1
+```
+
+The first pin is the output pin and the second is the input pin.
+
+Some keyboards have unused intersections in the key matrix. This setting uses one of these unused intersections to determine the handness.
+
+Normally, when a diode is connected to an intersection, it is judged to be left. If you add the following definition, it will be judged to be right.
+
+```c
+#define SPLIT_HAND_MATRIX_GRID_LOW_IS_RIGHT
+```
+
 #### Handedness by EEPROM
 
 This method sets the keyboard's handedness by setting a flag in the persistent storage (`EEPROM`).  This is checked when the controller first starts up, and determines what half the keyboard is, and how to orient the keyboard layout.