1 /*
2 * Copyright (c) 2022 Libre Solar Technologies GmbH
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 #include <zephyr/kernel.h>
8 #include <zephyr/device.h>
9 #include <zephyr/drivers/uart.h>
10
11 #include <string.h>
12
13 /* change this to any other UART peripheral if desired */
14 #define UART_DEVICE_NODE DT_CHOSEN(zephyr_shell_uart)
15
16 #define MSG_SIZE 32
17
18 /* queue to store up to 10 messages (aligned to 4-byte boundary) */
19 K_MSGQ_DEFINE(uart_msgq, MSG_SIZE, 10, 4);
20
21 static const struct device *const uart_dev = DEVICE_DT_GET(UART_DEVICE_NODE);
22
23 /* receive buffer used in UART ISR callback */
24 static char rx_buf[MSG_SIZE];
25 static int rx_buf_pos;
26
27 /*
28 * Read characters from UART until line end is detected. Afterwards push the
29 * data to the message queue.
30 */
serial_cb(const struct device * dev,void * user_data)31 void serial_cb(const struct device *dev, void *user_data)
32 {
33 uint8_t c;
34
35 if (!uart_irq_update(uart_dev)) {
36 return;
37 }
38
39 if (!uart_irq_rx_ready(uart_dev)) {
40 return;
41 }
42
43 /* read until FIFO empty */
44 while (uart_fifo_read(uart_dev, &c, 1) == 1) {
45 if ((c == '\n' || c == '\r') && rx_buf_pos > 0) {
46 /* terminate string */
47 rx_buf[rx_buf_pos] = '\0';
48
49 /* if queue is full, message is silently dropped */
50 k_msgq_put(&uart_msgq, &rx_buf, K_NO_WAIT);
51
52 /* reset the buffer (it was copied to the msgq) */
53 rx_buf_pos = 0;
54 } else if (rx_buf_pos < (sizeof(rx_buf) - 1)) {
55 rx_buf[rx_buf_pos++] = c;
56 }
57 /* else: characters beyond buffer size are dropped */
58 }
59 }
60
61 /*
62 * Print a null-terminated string character by character to the UART interface
63 */
print_uart(char * buf)64 void print_uart(char *buf)
65 {
66 int msg_len = strlen(buf);
67
68 for (int i = 0; i < msg_len; i++) {
69 uart_poll_out(uart_dev, buf[i]);
70 }
71 }
72
main(void)73 int main(void)
74 {
75 char tx_buf[MSG_SIZE];
76
77 if (!device_is_ready(uart_dev)) {
78 printk("UART device not found!");
79 return 0;
80 }
81
82 /* configure interrupt and callback to receive data */
83 int ret = uart_irq_callback_user_data_set(uart_dev, serial_cb, NULL);
84
85 if (ret < 0) {
86 if (ret == -ENOTSUP) {
87 printk("Interrupt-driven UART API support not enabled\n");
88 } else if (ret == -ENOSYS) {
89 printk("UART device does not support interrupt-driven API\n");
90 } else {
91 printk("Error setting UART callback: %d\n", ret);
92 }
93 return 0;
94 }
95 uart_irq_rx_enable(uart_dev);
96
97 print_uart("Hello! I'm your echo bot.\r\n");
98 print_uart("Tell me something and press enter:\r\n");
99
100 /* indefinitely wait for input from the user */
101 while (k_msgq_get(&uart_msgq, &tx_buf, K_FOREVER) == 0) {
102 print_uart("Echo: ");
103 print_uart(tx_buf);
104 print_uart("\r\n");
105 }
106 return 0;
107 }
108
