blob: 764b0a287f0258e5e4655b2e19663ff0a14056fa [file] [log] [blame]
/* rtt_console.c - Console messages to a RAM buffer that is then read by
* the Segger J-Link debugger
*/
/*
* Copyright (c) 2016 Nordic Semiconductor ASA
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <kernel.h>
#include <misc/printk.h>
#include <device.h>
#include <init.h>
#include <SEGGER_RTT.h>
extern void __printk_hook_install(int (*fn)(int));
extern void __stdout_hook_install(int (*fn)(int));
static bool host_present;
/** @brief Wait for fixed period.
*
*/
static void wait(void)
{
if (k_is_in_isr()) {
if (IS_ENABLED(CONFIG_RTT_TX_RETRY_IN_INTERRUPT)) {
k_busy_wait(1000*CONFIG_RTT_TX_RETRY_DELAY_MS);
}
} else {
k_sleep(CONFIG_RTT_TX_RETRY_DELAY_MS);
}
}
static int rtt_console_out(int character)
{
char c = (char)character;
unsigned int cnt;
int max_cnt = CONFIG_RTT_TX_RETRY_CNT;
do {
SEGGER_RTT_LOCK();
cnt = SEGGER_RTT_WriteNoLock(0, &c, 1);
SEGGER_RTT_UNLOCK();
/* There are two possible reasons for not writing any data to
* RTT:
* - The host is not connected and not reading the data.
* - The buffer got full and will be read by the host.
* These two situations are distinguished using the following
* algorithm:
* At the beginning, the module assumes that the host is active,
* so when no data is read, it busy waits and retries.
* If, after retrying, the host reads the data, the module
* assumes that the host is active. If it fails, the module
* assumes that the host is inactive and stores that
* information. On next call, only one attempt takes place.
* The host is marked as active if the attempt is successful.
*/
if (cnt) {
/* byte processed - host is present. */
host_present = true;
} else if (host_present) {
if (max_cnt) {
wait();
max_cnt--;
continue;
} else {
host_present = false;
}
}
break;
} while (1);
return character;
}
static int rtt_console_init(struct device *d)
{
ARG_UNUSED(d);
__printk_hook_install(rtt_console_out);
__stdout_hook_install(rtt_console_out);
return 0;
}
SYS_INIT(rtt_console_init, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT);