Import of the watch repository from Pebble

src/fw/drivers/fpc_pinstrap/fpc_pinstrap_snowy.c

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "drivers/fpc_pinstrap.h"
+
+#include "board/board.h"
+#include "drivers/gpio.h"
+
+static uint8_t prv_read_pinstrap_pin(InputConfig pin) {
+  // Read the pin value with it pulled up
+  gpio_input_init_pull_up_down(&pin, GPIO_PuPd_UP);
+  const bool pull_up_value = gpio_input_read(&pin);
+
+  // If the pull up was high, that either means it's actually high or floating. Read the
+  // pin again with a pull down to differentiate.
+
+  gpio_input_init_pull_up_down(&pin, GPIO_PuPd_DOWN);
+  const bool pull_down_value = gpio_input_read(&pin);
+
+  // Reset the pin to an analog input when we're not using it to reduce power draw.
+  gpio_analog_init(&pin);
+
+  if (pull_down_value != pull_up_value) {
+    // The value changed based on the pullup so it's floating.
+    return 2;
+  }
+  // It's not floating, return what the initial read told us.
+  return pull_up_value ? 1 : 0;
+}
+
+uint8_t fpc_pinstrap_get_value(void) {
+  // This is an uncommon operation so just configure the GPIOs as needed.
+
+  if (BOARD_CONFIG.fpc_pinstrap_1.gpio == GPIO_Port_NULL) {
+    return FPC_PINSTRAP_NOT_AVAILABLE;
+  }
+
+  return (prv_read_pinstrap_pin(BOARD_CONFIG.fpc_pinstrap_1) * 3)
+         + prv_read_pinstrap_pin(BOARD_CONFIG.fpc_pinstrap_2);
+}