1 /* rtt_console.c - Console messages to a RAM buffer that is then read by
2 * the Segger J-Link debugger
3 */
4
5 /*
6 * Copyright (c) 2016 Nordic Semiconductor ASA
7 *
8 * SPDX-License-Identifier: Apache-2.0
9 */
10
11
12 #include <zephyr/kernel.h>
13 #include <zephyr/sys/printk.h>
14 #include <zephyr/device.h>
15 #include <zephyr/init.h>
16 #include <SEGGER_RTT.h>
17
18 extern void __printk_hook_install(int (*fn)(int));
19 extern void __stdout_hook_install(int (*fn)(int));
20
21 static bool host_present;
22
23 /** @brief Wait for fixed period.
24 *
25 */
wait(void)26 static void wait(void)
27 {
28 if (!IS_ENABLED(CONFIG_MULTITHREADING) || k_is_in_isr()) {
29 if (IS_ENABLED(CONFIG_RTT_TX_RETRY_IN_INTERRUPT)) {
30 k_busy_wait(1000*CONFIG_RTT_TX_RETRY_DELAY_MS);
31 }
32 } else {
33 k_msleep(CONFIG_RTT_TX_RETRY_DELAY_MS);
34 }
35 }
36
rtt_console_out(int character)37 static int rtt_console_out(int character)
38 {
39 char c = (char)character;
40 unsigned int cnt;
41 int max_cnt = CONFIG_RTT_TX_RETRY_CNT;
42
43 do {
44 SEGGER_RTT_LOCK();
45 cnt = SEGGER_RTT_WriteNoLock(0, &c, 1);
46 SEGGER_RTT_UNLOCK();
47
48 /* There are two possible reasons for not writing any data to
49 * RTT:
50 * - The host is not connected and not reading the data.
51 * - The buffer got full and will be read by the host.
52 * These two situations are distinguished using the following
53 * algorithm:
54 * At the beginning, the module assumes that the host is active,
55 * so when no data is read, it busy waits and retries.
56 * If, after retrying, the host reads the data, the module
57 * assumes that the host is active. If it fails, the module
58 * assumes that the host is inactive and stores that
59 * information. On next call, only one attempt takes place.
60 * The host is marked as active if the attempt is successful.
61 */
62 if (cnt) {
63 /* byte processed - host is present. */
64 host_present = true;
65 } else if (host_present) {
66 if (max_cnt) {
67 wait();
68 max_cnt--;
69 continue;
70 } else {
71 host_present = false;
72 }
73 }
74
75 break;
76 } while (1);
77
78 return character;
79 }
80
rtt_console_init(void)81 static int rtt_console_init(void)
82 {
83
84 #ifdef CONFIG_PRINTK
85 __printk_hook_install(rtt_console_out);
86 #endif
87 __stdout_hook_install(rtt_console_out);
88
89 return 0;
90 }
91
92 SYS_INIT(rtt_console_init, PRE_KERNEL_1, CONFIG_CONSOLE_INIT_PRIORITY);
93
