Add support for Geistmaschine Macropod (#20116)

Co-authored-by: Pablo Martínez <58857054+elpekenin@users.noreply.github.com>

keyboards/geistmaschine/macropod/matrix.c

@@ -0,0 +1,87 @@
+/* Copyright 2023 ebastler and elpekenin
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "pca9555.h"
+#include "quantum.h"
+
+// PCA9555 i2c address, 0x20: A0 = 0, A1 = 0, A2 = 0
+#define IC1 0x20
+
+// Define how long to wait to reach the IO expander after connection loss again
+// Since this board is modular, it should not spam unnecessary i2c requests if used without a module
+#define RETRY_TIMESPAN 2000
+
+typedef enum {
+    PLUGGED,
+    DOUBTFUL,
+    UNPLUGGED
+} expander_status_t;
+
+void pca9555_setup(void) {
+    // Initialize the expander, no need to set ports to inputs as that is the default behavior
+    pca9555_init(IC1);
+}
+
+void matrix_init_custom(void) {
+    // Encoder pushbutton on the MCU is connected to PD2
+    setPinInputHigh(D2);
+    pca9555_setup();
+}
+
+bool matrix_scan_custom(matrix_row_t current_matrix[]) {
+    static expander_status_t status      = DOUBTFUL;
+    static uint32_t          retry_timer = 0;
+
+    // initialize one byte filled with 1
+    uint8_t pin_states = 0xFF;
+    
+    
+    if (status != UNPLUGGED || timer_elapsed32(retry_timer) > RETRY_TIMESPAN) {
+        // If the chip was unplugged before, it needs to be re-initialized
+        if(status==UNPLUGGED) {
+            pca9555_setup();
+        }
+        // Read the entire port into this byte, 1 = not pressed, 0 = pressed
+        bool ret = pca9555_readPins(IC1, PCA9555_PORT0, &pin_states);
+
+        // Update state
+        if (ret) {
+            status = PLUGGED;
+        } else {
+            switch (status) {
+                case PLUGGED:
+                    status = DOUBTFUL;
+                    break;
+
+                case DOUBTFUL:
+                    status = UNPLUGGED;
+                    break;
+
+                // If we've diagnosed as unplugged, update timer to not read I2C
+                case UNPLUGGED:
+                    retry_timer = timer_read32();
+            }
+        }
+    }
+
+    // Shift pin states by 1 to make room for the switch connected to the MCU, then OR them together and invert (as QMK uses inverted logic compared to the electrical levels)
+    matrix_row_t data = ~(pin_states << 1 | readPin(D2));
+
+    bool changed = current_matrix[0] != data;
+    current_matrix[0] = data;
+
+    return changed;
+}