Add mozc dial version.

Co-authored-by: Takashi Toyoshima <toyoshim@google.com>
Co-authored-by: Shun Ikejima <ikejima@google.com>

mozc-dial/firmware/common/photo_sensor.cc

@@ -0,0 +1,32 @@
+// Copyright 2025 Google Inc.
+// Use of this source code is governed by an Apache License that can be found
+// in the LICENSE file.
+
+#include "photo_sensor.h"
+
+#include "hardware/gpio.h"
+
+PhotoSensor::PhotoSensor(int8_t bit0,
+                         int8_t bit1,
+                         int8_t bit2,
+                         int8_t bit3,
+                         int8_t bit4,
+                         int8_t bit5)
+    : bits({bit0, bit1, bit2, bit3, bit4, bit5}) {
+  for (int8_t gpio : bits) {
+    gpio_init(gpio);
+    gpio_set_dir(gpio, GPIO_IN);
+    gpio_pull_up(gpio);  // Built-in 50-80K pull-up
+  }
+}
+
+uint8_t PhotoSensor::Read() {
+  uint8_t value = 0;
+  for (size_t bit = 0; bit < bits.size(); ++bit) {
+    if (bits[bit] == kNotUsed) {
+      break;
+    }
+    value |= gpio_get(bits[bit]) ? (1 << bit) : 0;
+  }
+  return value;
+}