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