samples: led: pwm: add decreasing brightness logic

Add a decreasing brightness phase to the sample's logic.

Signed-off-by: Yishai Jaffe <[email protected]>

Author: yishai1999

samples/drivers/led/pwm/README.rst

@@ -20,6 +20,7 @@ For each PWM LEDs (one after the other):
 - Turning on
 - Turning off
 - Increasing brightness gradually
+- Decreasing brightness gradually
 - Blinking on: 0.1 sec, off: 0.1 sec
 - Blinking on: 1 sec, off: 1 sec
 - Turning off

samples/drivers/led/pwm/sample.yaml

@@ -17,6 +17,7 @@ tests:
         - "Turned on"
         - "Turned off"
         - "Increasing brightness gradually"
+        - "Decreasing brightness gradually"
         - "Blinking on: ([0-9]+) msec, off: ([0-9]+) msec"
         - "(Blinking on: ([0-9]+) msec, off: ([0-9]+) msec|Cycle period not supported)"
         - "Turned off, loop end"

samples/drivers/led/pwm/src/main.c

@@ -33,7 +33,7 @@ const int num_leds = ARRAY_SIZE(led_label);
 static void run_led_test(const struct device *led_pwm, uint8_t led)
 {
 	int err;
-	uint16_t level;
+	int16_t level;
 
 	LOG_INF("Testing LED %d - %s", led, led_label[led] ? : "no label");
 
@@ -67,6 +67,18 @@ static void run_led_test(const struct device *led_pwm, uint8_t led)
 	}
 	k_sleep(K_MSEC(1000));
 
+	/* Decrease LED brightness gradually down to the minimum level. */
+	LOG_INF("  Decreasing brightness gradually");
+	for (level = MAX_BRIGHTNESS; level >= 0; level--) {
+		err = led_set_brightness(led_pwm, led, level);
+		if (err < 0) {
+			LOG_ERR("err=%d brightness=%d\n", err, level);
+			return;
+		}
+		k_sleep(K_MSEC(CONFIG_FADE_DELAY));
+	}
+	k_sleep(K_MSEC(1000));
+
 #if CONFIG_BLINK_DELAY_SHORT > 0
 	/* Start LED blinking (short cycle) */
 	err = led_blink(led_pwm, led, CONFIG_BLINK_DELAY_SHORT, CONFIG_BLINK_DELAY_SHORT);