add DIP_SWITCH_MATRIX_GRID support

docs/feature_dip_switch.md

@@ -7,9 +7,17 @@ DIP switches are supported by adding this to your `rules.mk`:
 and this to your `config.h`:
 
 ```c
+// Connects each switch in the dip switch to the GPIO pin of the MCU
 #define DIP_SWITCH_PINS { B14, A15, A10, B9 }
 ```
 
+or
+
+```c
+// Connect each switch in the DIP switch to an unused intersections in the key matrix.
+#define DIP_SWITCH_MATRIX_GRID { {0,6}, {1,6}, {2,6} } // List of row and col pairs
+```
+
 ## Callbacks
 
 The callback functions can be inserted into your `<keyboard>.c`:
@@ -87,4 +95,10 @@ void dip_switch_update_mask_user(uint32_t state) {
 
 ## Hardware
 
+### Connects each switch in the dip switch to the GPIO pin of the MCU
+
 One side of the DIP switch should be wired directly to the pin on the MCU, and the other side to ground.  It should not matter which side is connected to which, as it should be functionally the same. 
+
+### Connect each switch in the DIP switch to an unused intersections in the key matrix.
+
+As with the keyswitch, a diode and DIP switch connect the ROW line to the COL line.

quantum/dip_switch.c

@@ -21,12 +21,31 @@
 // for memcpy
 #include <string.h>
 
-#if !defined(DIP_SWITCH_PINS)
-#    error "No DIP switch pads defined by DIP_SWITCH_PINS"
+#if !defined(DIP_SWITCH_PINS) && !defined(DIP_SWITCH_MATRIX_GRID)
+#    error "Either DIP_SWITCH_PINS or DIP_SWITCH_MATRIX_GRID must be defined."
 #endif
 
-#define NUMBER_OF_DIP_SWITCHES (sizeof(dip_switch_pad) / sizeof(pin_t))
-static pin_t dip_switch_pad[]                              = DIP_SWITCH_PINS;
+#if defined(DIP_SWITCH_PINS) && defined(DIP_SWITCH_MATRIX_GRID)
+#    error "Both DIP_SWITCH_PINS and DIP_SWITCH_MATRIX_GRID are defined."
+#endif
+
+#ifdef DIP_SWITCH_PINS
+#    define NUMBER_OF_DIP_SWITCHES (sizeof(dip_switch_pad) / sizeof(pin_t))
+static pin_t dip_switch_pad[] = DIP_SWITCH_PINS;
+#endif
+
+#ifdef DIP_SWITCH_MATRIX_GRID
+typedef struct matrix_index_t {
+    uint8_t row;
+    uint8_t col;
+} matrix_index_t;
+
+#    define NUMBER_OF_DIP_SWITCHES (sizeof(dip_switch_pad) / sizeof(matrix_index_t))
+static matrix_index_t dip_switch_pad[] = DIP_SWITCH_MATRIX_GRID;
+extern bool peek_matrix(uint8_t row_index, uint8_t col_index, bool read_raw);
+static uint16_t scan_count;
+#endif /* DIP_SWITCH_MATRIX_GRID */
+
 static bool  dip_switch_state[NUMBER_OF_DIP_SWITCHES]      = {0};
 static bool  last_dip_switch_state[NUMBER_OF_DIP_SWITCHES] = {0};
 
@@ -39,18 +58,43 @@ __attribute__((weak)) void dip_switch_update_mask_user(uint32_t state) {}
 __attribute__((weak)) void dip_switch_update_mask_kb(uint32_t state) { dip_switch_update_mask_user(state); }
 
 void dip_switch_init(void) {
+#ifdef DIP_SWITCH_PINS
     for (uint8_t i = 0; i < NUMBER_OF_DIP_SWITCHES; i++) {
         setPinInputHigh(dip_switch_pad[i]);
     }
     dip_switch_read(true);
+#endif
+#ifdef DIP_SWITCH_MATRIX_GRID
+    scan_count = 0;
+#endif
 }
 
 void dip_switch_read(bool forced) {
     bool     has_dip_state_changed = false;
     uint32_t dip_switch_mask       = 0;
 
+#ifdef DIP_SWITCH_MATRIX_GRID
+    bool     read_raw = false;
+
+    if (scan_count < 500) {
+        scan_count ++;
+        if (scan_count == 10) {
+            read_raw = true;
+            forced = true;  /* First reading of the dip switch */
+        } else {
+            return;
+        }
+    }
+#endif
+
     for (uint8_t i = 0; i < NUMBER_OF_DIP_SWITCHES; i++) {
+#ifdef DIP_SWITCH_PINS
         dip_switch_state[i] = !readPin(dip_switch_pad[i]);
+#endif
+#ifdef DIP_SWITCH_MATRIX_GRID
+        dip_switch_state[i] = peek_matrix(dip_switch_pad[i].row, dip_switch_pad[i].col,
+                                          read_raw);
+#endif
         dip_switch_mask |= dip_switch_state[i] << i;
         if (last_dip_switch_state[i] != dip_switch_state[i] || forced) {
             has_dip_state_changed = true;

quantum/matrix_common.c

@@ -112,3 +112,8 @@ __attribute__((weak)) uint8_t matrix_scan(void) {
     matrix_scan_quantum();
     return changed;
 }
+
+__attribute__((weak)) bool peek_matrix(uint8_t row_index, uint8_t col_index, bool raw) {
+    return 0 != ( (raw? raw_matrix[row_index]:matrix[row_index])
+                  & (MATRIX_ROW_SHIFTER << col_index));
+}