Initial commit

app/drivers/sensor/wpm/wpm.c

@@ -0,0 +1,76 @@
+
+#define WPM_BUFFER_LENGTH 15
+#define WPM_INTERVAL 300
+#define WPM_SIGMA 15
+#define WPM_STROKES_PER_WORD 5
+
+struct wpm_data {
+    const struct sensor_trigger *trigger;
+    sensor_trigger_handler_t handler;
+};
+
+/**
+ * Holds the number of keystrokes between subsequent WPM re-calculations.
+ * At 300ms intervals, a 15 element buffer covers the last 4.5s.
+ */
+static uint8_t keystrokes = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+
+/**
+ * Indicates where the keystrokes buffer currently ends.
+ */
+static uint8_t keystrokes_index = 0;
+
+/**
+ * Current WPM value.
+ */
+static uint8_t wpm = 0;
+
+static void wpm_calc(struct k_work *work);
+
+K_WORK_DEFINE(wpm_work, wpm_calc);
+
+static void wpm_tick_handler(struct k_timer *timer) { k_work_submit(&wpm_calc); }
+
+K_TIMER_DEFINE(wpm_tick, wpm_tick_handler, NULL);
+
+static void wpm_calc(struct k_work *work) {
+    uint8_t total_keystrokes = 0;
+
+    float averages = 0.0;
+    float weights = 0.0;
+
+    for (size_t i = 0; i < WPM_BUFFER_LENGTH; ++i) {
+        float distance = keystrokes_index - i + (i > keystrokes_index ? WPM_BUFFER_LENGTH : 0);
+        float weight = exp(-((distance * distance) / (2 * WPM_SIGMA)));
+
+        weights += weight;
+        averages += weight * keystrokes[i];
+
+        total_keystrokes += keystrokes[i];
+    }
+
+    uint8_t new_wpm = ((averages / weights) * ((1000 * 60) / WPM_INTERVAL)) / WPM_STROKES_PER_WORD;
+
+    if (++keystrokes_index == WPM_CALC_BUFFER_LENGTH) {
+        keystrokes_index = 0;
+    }
+
+    keystrokes[keystrokes_index] = 0;
+
+    if (total_keystrokes == 0) {
+        k_timer_stop(&wpm_tick);
+    }
+}
+
+static int wpm_trigger_set(const struct device *dev, const struct sensor_trigger *trigger,
+                           sensor_trigger_handler_t handler) {
+    struct wpm_data *data = dev->data;
+
+    data->trigger = trigger;
+    data->handler = handler;
+
+    return 0;
+}
+
+#define WPM_SENSOR_DEVICE(idx)
+\