1 /*
2 * Copyright (c) 2016 Intel Corporation
3 * Copyright (c) 2020 Nordic Semiconductor ASA
4 *
5 * SPDX-License-Identifier: Apache-2.0
6 */
7
8 /**
9 * @file Sample app to demonstrate PWM.
10 */
11
12 #include <zephyr/kernel.h>
13 #include <zephyr/sys/printk.h>
14 #include <zephyr/device.h>
15 #include <zephyr/drivers/pwm.h>
16
17 static const struct pwm_dt_spec pwm_led0 = PWM_DT_SPEC_GET(DT_ALIAS(pwm_led0));
18
19 #define MIN_PERIOD PWM_SEC(1U) / 128U
20 #define MAX_PERIOD PWM_SEC(1U)
21
main(void)22 int main(void)
23 {
24 uint32_t max_period;
25 uint32_t period;
26 uint8_t dir = 0U;
27 int ret;
28
29 printk("PWM-based blinky\n");
30
31 if (!pwm_is_ready_dt(&pwm_led0)) {
32 printk("Error: PWM device %s is not ready\n",
33 pwm_led0.dev->name);
34 return 0;
35 }
36
37 /*
38 * In case the default MAX_PERIOD value cannot be set for
39 * some PWM hardware, decrease its value until it can.
40 *
41 * Keep its value at least MIN_PERIOD * 4 to make sure
42 * the sample changes frequency at least once.
43 */
44 printk("Calibrating for channel %d...\n", pwm_led0.channel);
45 max_period = MAX_PERIOD;
46 while (pwm_set_dt(&pwm_led0, max_period, max_period / 2U)) {
47 max_period /= 2U;
48 if (max_period < (4U * MIN_PERIOD)) {
49 printk("Error: PWM device "
50 "does not support a period at least %lu\n",
51 4U * MIN_PERIOD);
52 return 0;
53 }
54 }
55
56 printk("Done calibrating; maximum/minimum periods %u/%lu nsec\n",
57 max_period, MIN_PERIOD);
58
59 period = max_period;
60 while (1) {
61 ret = pwm_set_dt(&pwm_led0, period, period / 2U);
62 if (ret) {
63 printk("Error %d: failed to set pulse width\n", ret);
64 return 0;
65 }
66 printk("Using period %d\n", period);
67
68 period = dir ? (period * 2U) : (period / 2U);
69 if (period > max_period) {
70 period = max_period / 2U;
71 dir = 0U;
72 } else if (period < MIN_PERIOD) {
73 period = MIN_PERIOD * 2U;
74 dir = 1U;
75 }
76
77 k_sleep(K_SECONDS(4U));
78 }
79 return 0;
80 }
81
