02_uart

apps/02_uart/src/main.c

@@ -0,0 +1,94 @@
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/devicetree.h>
+#include <zephyr/sys/printk.h>
+#include <zephyr/drivers/gpio.h>
+#include <zephyr/drivers/uart.h>
+
+// Use the board's chosen console UART
+#define UART_NODE DT_CHOSEN(zephyr_console)
+#define UART_RX_QUEUE_SIZE 16
+
+#if !DT_NODE_HAS_STATUS(DT_ALIAS(led0), okay)
+#error "Board does not define alias led0. Add a board overlay"
+#endif
+
+static const struct gpio_dt_spec led_red =
+    GPIO_DT_SPEC_GET(DT_ALIAS(led0), gpios);
+
+#if !DT_NODE_HAS_STATUS(UART_NODE, okay)
+#error "UART console not available. Add a board overlay"
+#endif
+
+static const struct device *const uart_dev = 
+	DEVICE_DT_GET(UART_NODE);
+
+/* Do not poll the STM32F4 UART only once per application loop. Its receive
+ * data register can hold just one byte, so a second byte causes an overrun.
+ * Store received bytes from the UART interrupt until the main thread handles
+ * them.
+ */
+K_MSGQ_DEFINE(uart_rx_queue, sizeof(uint8_t), UART_RX_QUEUE_SIZE, 1);
+
+static void uart_rx_isr(const struct device *dev, void *user_data) {
+	uint8_t ch;
+
+	ARG_UNUSED(user_data);
+
+	if (!uart_irq_update(dev) || !uart_irq_rx_ready(dev)) {
+		return;
+	}
+
+	while (uart_fifo_read(dev, &ch, 1) == 1) {
+		// Drop the newest byte if the application queue is full
+		(void)k_msgq_put(&uart_rx_queue, &ch, K_NO_WAIT);
+	}
+}
+
+int main(void)
+{
+	uint32_t cnt = 0;
+	uint8_t ch;
+	int rc;
+
+	if (!gpio_is_ready_dt(&led_red)) {
+		printk("LED GPIO is not ready\r\n");
+		return 0;
+	}
+
+	rc = gpio_pin_configure_dt(&led_red, GPIO_OUTPUT_INACTIVE);
+	if (rc != 0) {
+		printk("Failed to configure LED GPIO: %d\r\n", rc);
+		return 0;
+	}
+
+	if (!device_is_ready(uart_dev)) {
+		return 0;
+	}
+
+	rc = uart_irq_callback_user_data_set(uart_dev, uart_rx_isr, NULL);
+	if (rc != 0) {
+		printk("Failed to configure UART RX interrupt: %d\r\n", rc);
+		return 0;
+	}
+	uart_irq_rx_enable(uart_dev);
+
+	printk("\r\n[UART]: Send O to turn LED on, F to turn it off\r\n");
+
+	while (1) {
+		while (k_msgq_get(&uart_rx_queue, &ch, K_NO_WAIT) == 0) {
+			if (ch == 'O' || ch == 'o') {
+				(void)gpio_pin_set_dt(&led_red, 1);
+				printk("LED on\r\n");
+			} else if (ch == 'F' || ch == 'f') {
+				(void)gpio_pin_set_dt(&led_red, 0);
+				printk("LED off\r\n");
+			}
+		}
+
+		printk("Tick: %u\r\n", cnt++);
+		k_msleep(200);
+	}
+
+	return 0;
+}