Minimal SEGGER RTT logging demo for EK-RA8D2. More...

#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include "ra8_attributes.h"
#include "ra8_board_ek_ra8d2.h"
#include "ra8_boot_entry.h"
#include "ra8_cgc.h"
#include "ra8_err.h"
#include "ra8_isr.h"
#include "ra8_time.h"

Include dependency graph for main.c:

Data Structures
struct	rtt_buf_t
	One direction of an RTT channel (matches SEGGER layout). More...
struct	rtt_cb_t
	SEGGER RTT control block. More...

Enumerations
enum	rtt_demo_const_t : uint32_t { k_rtt_demo_period_ms = 1000U , k_rtt_up_buf_bytes = 1024U , k_rtt_down_buf_bytes = 32U , k_rtt_decimal_base = 10U , k_rtt_max_digits = 10U , k_rtt_msg_buf_bytes = 32U }
	Demo tunables. More...

Functions
static void	internal_panic_halt (void)
	Park the core after an unrecoverable RTT demo failure.
static void	internal_init (void)
	Initialise the RTT control block in place.
static ra8_err_t	internal_write (const uint8_t *data, uint32_t len)
	Push `len` bytes into channel 0's up-buffer (non-blocking).
static uint8_t	internal_format_line (uint32_t counter, char *buf)
	Format "rtt_log_demo: NNN\r\n" into `buf`.
static void	internal_setup_or_halt (void)
	Bring CGC + SysTick + LED1 + RTT control block up.
void	main (void)
	Publish a monotonically increasing RTT line once per second.

Variables
static uint8_t	s_rtt_up_buf [k_rtt_up_buf_bytes]
	Up-buffer storage for channel 0.
static uint8_t	s_rtt_down_buf [k_rtt_down_buf_bytes]
	Down-buffer storage for channel 0.
static rtt_cb_t	s_rtt_cb
	The control block itself.

Detailed Description

Minimal SEGGER RTT logging demo for EK-RA8D2.

Tag: [Ring 6 / APP] {World: S}

Allocates a SEGGER-compatible RTT control block in SRAM and writes a counter line into the up-buffer once per second. The on-board J-Link OB picks the block up by scanning RAM for the magic string "SEGGER RTT"; JLinkRTTViewer on the host then renders the stream live with no UART pin needed.

The control-block layout matches SEGGER_RTT.h (ring buffer with read/write indices). Channel 0 is the standard "Terminal" up-buffer. We keep a 1 KiB up-buffer and a 32 byte down-buffer (unused here).

Sequence:

ra8_cgc_init – bring the chip up to the canonical clock tree.
ra8_time_init – 1 ms SysTick.
Initialise the RTT control block in BSS (idempotent).
Loop: rtt_write a counter line, toggle LED1, sleep 1 s.

Copyright: Copyright (c) 2026 Brighton Sikarskie SPDX-License-Identifier: MIT

Since: 0.1.0

Definition in file main.c.

Enumeration Type Documentation

◆ rtt_demo_const_t

enum rtt_demo_const_t : uint32_t

Demo tunables.

Enumerator
k_rtt_demo_period_ms	Rtt demo period ms.
k_rtt_up_buf_bytes	Rtt up buffer bytes.
k_rtt_down_buf_bytes	Rtt down buffer bytes.
k_rtt_decimal_base	Rtt decimal base.
k_rtt_max_digits	Rtt maximum digits.
k_rtt_msg_buf_bytes	Rtt message buffer bytes.

Definition at line 43 of file main.c.

Function Documentation

◆ internal_format_line()

uint8_t internal_format_line	(	uint32_t	counter,
		char *	buf )

static

Format "rtt_log_demo: NNN\r\n" into buf.

Copies the fixed prefix, converts the counter through a bounded reverse digit buffer, and appends CRLF without a NUL terminator.

Parameters

[in]	counter	Number to render in base-10 ASCII.
[out]	buf	Output buffer (>= k_rtt_msg_buf_bytes).

Returns: Number of bytes written.

Return values

17..26 Complete line length, depending on counter width.

Precondition: buf points to at least k_rtt_msg_buf_bytes writable bytes.; counter is a complete 32-bit sample.

Postcondition: The returned prefix of buf contains one CRLF-terminated line.; No byte beyond the returned count is modified.

Note: Reentrant when callers provide distinct output buffers.

Since: 0.1.0

Definition at line 199 of file main.c.

References k_rtt_decimal_base, k_rtt_max_digits, and RA8_INTERNAL.

◆ internal_init()

void internal_init ( void )

static

Initialise the RTT control block in place.

The id is written byte-by-byte (rather than as a string literal) so a search for "SEGGER RTT" in the firmware image only matches the runtime control block, not a stale literal pool entry.

Precondition: Called once before the first internal_write.; The file-scope control block and buffers occupy writable SRAM.

Postcondition: s_rtt_cb.id begins with S E G G E R sp R T T.; Both channel descriptors use empty, bounded caller-owned rings.

Note: Not thread-safe; initialization replaces every descriptor field.

Since: 0.1.0

Definition at line 118 of file main.c.

References k_rtt_down_buf_bytes, k_rtt_up_buf_bytes, RA8_INTERNAL, s_rtt_cb, s_rtt_down_buf, and s_rtt_up_buf.

Referenced by internal_setup_or_halt().

◆ internal_panic_halt()

void internal_panic_halt ( void )

static

Park the core after an unrecoverable RTT demo failure.

Repeatedly executes WFI while preserving the ring and clock state.

Precondition: Called only from a fatal boot or terminal foreground path.; The caller does not require recovery without reset.

Postcondition: The core stays in WFI until external intervention.; No RTT producer index changes after entry.

Note: Not thread-safe; this is the terminal single-threaded path.

Since: 0.1.0

Definition at line 95 of file main.c.

References RA8_INTERNAL.

◆ internal_setup_or_halt()

void internal_setup_or_halt ( void )

static

Bring CGC + SysTick + LED1 + RTT control block up.

Initializes clocks, the delay service, LED1, and the in-SRAM RTT descriptor in dependency order, halting on a failed HAL operation.

Precondition: Reset startup initialized static storage and the vector table.; Called once before global interrupt enable.

Postcondition: On return, channel zero is ready for non-blocking firmware writes.; LED1 and the millisecond delay service are ready.

Note: Not thread-safe; it owns the demo's global initialization.

Since: 0.1.0

Definition at line 232 of file main.c.

References internal_init(), internal_panic_halt(), k_ra8_board_led1, k_ra8_clock_id_cpuclk0, k_ra8_ok, ra8_board_led_init(), ra8_cgc_get_clock_hz(), ra8_cgc_init(), RA8_INTERNAL, and ra8_time_init().

◆ internal_write()

ra8_err_t internal_write	(	const uint8_t *	data,
		uint32_t	len )

staticnodiscard

Push len bytes into channel 0's up-buffer (non-blocking).

MC/DC:: Compound decision: next == rd || size == 0. Two atomic conditions x N+1 = 3 vectors; the host test exercises full / empty / mid-buffer wrap independently.

Parameters

[in]	data	Bytes to enqueue.
[in]	len	Byte count; data fitting beyond head is dropped.

Returns: RTT producer status.

Return values

k_ra8_ok	Bytes were appended (or dropped silently).
k_ra8_err_null_ptr	data was NULL.

Precondition: internal_init configured channel zero and its backing buffer.; The host owns only rd_off while this producer owns wr_off.

Postcondition: Successfully enqueued bytes precede the published write offset.; The producer never advances into the consumer's current read slot.

Note: Single-producer only; not thread-safe across firmware writers.

Since: 0.1.0

Definition at line 163 of file main.c.

References rtt_buf_t::buf, k_ra8_err_null_ptr, k_ra8_ok, RA8_INTERNAL, rtt_buf_t::rd_off, s_rtt_cb, rtt_buf_t::size, and rtt_buf_t::wr_off.

Referenced by main().

◆ main()

void main ( void )

Publish a monotonically increasing RTT line once per second.

The application entry point Reset_Handler hands control to.

Initializes channel zero, formats and enqueues each counter line, toggles LED1, and delays before incrementing the next sample.

Precondition: Reset startup and SystemInit completed successfully.; J-Link may update only the consumer offset in the shared descriptor.

Postcondition: Each successful iteration advances the counter and toggles LED1.; Any producer or LED error leads to the terminal panic helper.

Note: Does not return during normal operation.

Since: 0.1.0

Definition at line 261 of file main.c.

References internal_format_line(), internal_panic_halt(), internal_setup_or_halt(), internal_write(), k_ra8_board_led1, k_ra8_ok, k_rtt_demo_period_ms, k_rtt_msg_buf_bytes, ra8_board_led_toggle(), ra8_delay_ms(), and ra8_isr_globals_enable().

Variable Documentation

◆ s_rtt_cb

rtt_cb_t s_rtt_cb

static

The control block itself.

Definition at line 83 of file main.c.

Referenced by internal_init(), and internal_write().

◆ s_rtt_down_buf

uint8_t s_rtt_down_buf[k_rtt_down_buf_bytes]

static

Down-buffer storage for channel 0.

Definition at line 80 of file main.c.

Referenced by internal_init().

◆ s_rtt_up_buf

uint8_t s_rtt_up_buf[k_rtt_up_buf_bytes]

static

Up-buffer storage for channel 0.

Definition at line 77 of file main.c.

Referenced by internal_init().

Data Structures

Enumerations

Functions

Variables

Detailed Description

Enumeration Type Documentation

◆ rtt_demo_const_t

Function Documentation

◆ internal_format_line()

◆ internal_init()

◆ internal_panic_halt()

◆ internal_setup_or_halt()

◆ internal_write()

◆ main()

Variable Documentation

◆ s_rtt_cb

◆ s_rtt_down_buf

◆ s_rtt_up_buf