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--- en:edu:zmitac:s2:aih:lab:nrf52zephyrtimers [2023/12/06 22:33] – [Zephyr work queue] ktokarz
+++ en:edu:zmitac:s2:aih:lab:nrf52zephyrtimers [2023/12/06 23:05] (current) – [Timer use] ktokarz
@@ Line 1: / Line 1: @@
-====== Zephyr timers ======
+====== Zephyr timers and work queues ======
 A timer in Zephyr OS is a kernel object that measures the time using the internal system clock. When a timer reaches a specified time limit it can carry an action as specified in the application. In an operating system, the timer entity is software-based opposite to the hardware timer unit implemented in the microcontroller. Software timers use hardware timers to operate, and in general, the operating system keeps time-dependent actions. Zephyr OS allows one to define the number of timers which can be used to measure periods, asynchronously start some actions, control LED blinking, etc.
-When the timer is fired the system work queue task is started. The system work queue is optional and it's defined by a kernel if any application makes use of it. It is available to any application or kernel code that requires work queue support. We will present the work queues in the next exercise.
+When the timer is fired the system work queue task is started. The system work queue is optional and it's defined by a kernel if any application makes use of it. It is available to any application or kernel code that requires work queue support. We will present the work queues at the end of this exercise.
 As with other tasks, the timer task should be as short as possible and non-blocking.
@@ Line 13: / Line 13: @@
 The timer object must be defined and initialized. Its function is automatically added to the system work queue as the task, so we don't need to do anything with the queue. Let's try to modify the blinky code from the first laboratory on GPIOs to add a second LED blinking as the result of timer expiration. First, we need to add the timer object declaration.
 <code>
-        struct k_timer led_timer;
+struct k_timer led_timer;
 </code>
 Next, we add the expiry function which will toggle the state of LED every call.
 <code>
 void led_timer_function(struct k_timer *timer_id)
-	{
+{
-		gpio_pin_set(led_dev, LED1_PIN, (int)led1_is_on);
+   gpio_pin_set(led_dev, LED1_PIN, (int)led1_is_on);
-		led1_is_on = !led1_is_on;
+   led1_is_on = !led1_is_on;
-	}
+}
 </code>
 In the main, we have to add two functions: one to initialize the timer, and a second for starting it.
 <code>
-	k_timer_init(&led_timer, led_timer_function, NULL);
+k_timer_init(&led_timer, led_timer_function, NULL);
-	k_timer_start(&led_timer, K_MSEC(200), K_MSEC(300));
+k_timer_start(&led_timer, K_MSEC(200), K_MSEC(300));
 </code>
 Of course, there is a need to add and configure a second LED. This can be done as LED0 in the blinky example so we are not going to repeat the detailed description here.
@@ Line 50: / Line 50: @@
 CONFIG_LOG=y
 CONFIG_SERIAL=y
+</code>
+The resulting code can look as follows:
+<code>
+/*
+ * Copyright (c) 2016 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include <zephyr.h>
+#include <device.h>
+#include <devicetree.h>
+#include <drivers/gpio.h>
+/* 1000 msec = 1 sec */
+#define SLEEP_TIME_MS   1000
+#define MY_TIMER_PERIOD 33
+/* The devicetree node identifier for the "led0" alias. */
+#define LED0_NODE DT_ALIAS(led0)
+#if DT_NODE_HAS_STATUS(LED0_NODE, okay)
+#define LED0	DT_GPIO_LABEL(LED0_NODE, gpios)
+#define PIN	DT_GPIO_PIN(LED0_NODE, gpios)
+#define FLAGS	DT_GPIO_FLAGS(LED0_NODE, gpios)
+#else
+/* A build error here means your board isn't set up to blink an LED. */
+#error "Unsupported board: led0 devicetree alias is not defined"
+#define LED0	""
+#define PIN	0
+#define FLAGS	0
+#endif
+#define LED1_NODE DT_ALIAS(led1)
+#if DT_NODE_HAS_STATUS(LED1_NODE, okay)
+#define LED1	DT_GPIO_LABEL(LED1_NODE, gpios)
+#define PIN1	DT_GPIO_PIN(LED1_NODE, gpios)
+#define FLAGS1	DT_GPIO_FLAGS(LED1_NODE, gpios)
+#else
+/* A build error here means your board isn't set up to blink an LED. */
+#error "Unsupported board: led0 devicetree alias is not defined"
+#define LED1	""
+#define PIN1	0
+#define FLAGS1	0
+#endif
+const struct device *led_dev;
+bool led1_is_on = true;
+struct k_timer led_timer;
+void led_timer_function(struct k_timer *timer_id)
+{
+   gpio_pin_set(led_dev, PIN1, (int)led1_is_on);
+   led1_is_on = !led1_is_on;
+}
+void main(void)
+{
+   const struct device *dev;
+   bool led_is_on = true;
+   int ret;
+   k_timer_init(&led_timer, led_timer_function, NULL);
+   k_timer_start(&led_timer, K_NO_WAIT, K_MSEC(MY_TIMER_PERIOD));
+   dev = device_get_binding(LED0);
+   if (dev == NULL) {
+   	return;
+   }
+   led_dev = device_get_binding(LED1);
+   if (led_dev == NULL) {
+	return;
+   }
+   ret = gpio_pin_configure(dev, PIN, GPIO_OUTPUT_ACTIVE | FLAGS);
+   if (ret < 0) {
+	return;
+   }
+   ret = gpio_pin_configure(led_dev, PIN1, GPIO_OUTPUT_ACTIVE | FLAGS1);
+   if (ret < 0) {
+	return;
+   }
+   while (1) {
+	gpio_pin_set(dev, PIN, (int)led_is_on);
+	led_is_on = !led_is_on;
+	k_msleep(SLEEP_TIME_MS);
+	printk("Timer ticks %d",k_timer_status_get(&led_timer));
+   }
+}
 </code>
@@ Line 62: / Line 157: @@
 then the function for the work item must be defined:
 <code>
-void my_work_item_function(struct k_work *my_work_item){
+void my_work_item_function(struct k_work *my_work_item)
-	printk("Work item executed\n");
+{
+   printk("Work item executed\n");
 }
 </code>
@@ Line 79: / Line 175: @@
 ===== Summary of the tasks for the laboratory =====
-. Modify the blink example according to the instructions presented above\\
+. Modify the blink example according to the instructions presented in the first part of the instruction\\
-. Add to the timer expiry function the line that is executed longer than the timer period. This can be the line as follows (adjust the max iteration value):
+. Add to the timer expiry function the line that is executed longer than the timer period. This can be the line as follows:
 <code>
-for (int i=0; i<40; i++) printk("counter = %d \n", i);
+for (int i=0; i<40; i++)
+{
+   printk("counter = %d \n", i);
+}
 </code>
-. Observe the results and explain them in the report.
+. Observe the results while adjusting the max iteration value, and explain observations in the report.\\
+. Add at the end of led_timer_function the line shown below and observe the behaviour of the program.
+<code>k_msleep(1);</code>
+. Define two work items with their functions. One for the code from the timer function, and the second for the code from the main function. Instead of executing the full code in the timer and main function submit corresponding work items. The code for the timer work item can look as follows (the code for the main function as well as the work items definition and initialization write on your own). Experiment with the maximal iteration value in the "for" loop. Describe observation results in the report.
+<code>
+void led_timer_function(struct k_timer *timer_id)
+{
+   gpio_pin_set(led_dev, PIN1, (int)led1_is_on);
+   led1_is_on = !led1_is_on;
+   k_work_submit(&timer_work_item);
+}
+void timer_work_item_function (struct k_work *timer_work_item)
+{
+   for (int i=0; i<40; i++)
+   {
+       printk("counter = %d \n", I);
+       k_msleep(1);
+   }
+}
+</code>