Interrupt-driven SCI8 UART echo for EK-RA8D2 (RXI / TXI / TEI). More...

#include <stdint.h>
#include "ra8_board_ek_ra8d2.h"
#include "ra8_boot_entry.h"
#include "ra8_cgc.h"
#include "ra8_elc.h"
#include "ra8_err.h"
#include "ra8_gpio_constants.h"
#include "ra8_isr.h"
#include "ra8_port_constants.h"
#include "ra8_port_utils.h"
#include "ra8_sci.h"
#include "ra8_time.h"

Include dependency graph for main.c:

Enumerations
enum	uart_irq_config_t : uint32_t { k_uart_irq_baud = 115200U , k_uart_irq_loop_ms = 100U , k_uart_irq_sci_chan = 8U , k_uart_irq_isr_prio = 4U }
	Compile-time settings for the echo demo. More...
enum	uart_irq_event_t : uint16_t { k_uart_irq_event_rxi = 0x122U , k_uart_irq_event_txi = 0x123U , k_uart_irq_event_tei = 0x124U }
	SCI8 ELC event numbers (FSP ra8d2 bsp_elc: RXI/TXI/TEI). More...

Functions
static void	uart_irq_panic_halt (void)
	Halt forever in WFI – panic stop on any init failure.
static void	uart_irq_rxi_isr (void *ctx)
	SCI8 RXI ISR: drive the driver's receive state machine.
static void	uart_irq_txi_isr (void *ctx)
	SCI8 TXI ISR: push the next byte of an in-flight interrupt TX.
static void	uart_irq_tei_isr (void *ctx)
	SCI8 TEI ISR: end-of-transmission housekeeping.
static void	uart_irq_rx_cb (void *ctx, uint8_t byte)
	RX byte callback: echo the byte and re-arm the next receive.
static ra8_err_t	uart_irq_pins_init (void)
	Route PD02 / PD03 to SCI8 TXD / RXD via the PFS PSEL field.
static ra8_err_t	uart_irq_register_isrs (void)
	Register the SCI8 RXI / TXI / TEI events with the NVIC.
static void	uart_irq_setup_or_halt (void)
	Bring CGC + SysTick + SCI8 + LED1 + the SCI ISRs up, or panic-halt.
void	main (void)
	Application entry.

Variables
static const ra8_port_pin_t	k_uart_irq_pin_txd = (ra8_port_pin_t)k_ra8_board_uart_console_pin_txd
	Pinout for the on-board J-Link OB CDC channel (SCI8 / PD02 + PD03).
static const ra8_port_pin_t	k_uart_irq_pin_rxd = (ra8_port_pin_t)k_ra8_board_uart_console_pin_rxd
static const uint8_t	k_uart_irq_banner [] = "uart_irq_echo ready\r\n"
	Banner printed once over the polled path so the host sees a prompt.
volatile uint32_t	g_uart_irq_echoes = 0U
	Count of bytes echoed from interrupt context.
static uint8_t	s_uart_irq_rx_byte
	One-byte RX landing pad re-armed by every receive callback.

Detailed Description

Interrupt-driven SCI8 UART echo for EK-RA8D2 (RXI / TXI / TEI).

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

Companion to uart_hello (which proves the polled SCI path): this app proves the interrupt-driven SCI path end to end – a receive byte raises RXI, the registered ISR drives ra8_sci_dispatch_rxi, the echo is queued with ra8_sci_write (which arms CCR0.TIE), and each TXI then pushes the next byte from ra8_sci_dispatch_txi until the frame drains. Nothing in the main loop touches the data path, so any byte echoed is proof the real NVIC -> ISR chain ran.

It brings the chip up exactly like uart_hello (CGC -> PLL, SCI8 TXD8 = PD02 / RXD8 = PD03 at 115200 8N1), then:

ra8_isr_init + ra8_isr_register for SCI8 RXI / TXI / TEI so each event links through the ICU IELSR table and enables its NVIC line.
Prints a one-line banner with ra8_sci_write_polling (so the polled path is exercised too, and the host sees a prompt).
Attaches an RX byte callback and arms a 1-byte interrupt receive with ra8_sci_read; the callback re-arms the next receive and echoes the byte back over the interrupt-driven transmitter.
Idles in ra8_delay_ms – every echoed byte happens in handler context.

On the EK-RA8D2 the SCI8 pins surface as the J-Link OB VCOM port; typing into a terminal at 115200 8N1 echoes each character back and toggles LED1. Under tools/ra8_emulator, --input <str> feeds the RX queue and the echo appears as captured [uart] output.

Note: Unlike the other demos, this one drives SCI8 directly rather than the BSP ra8_board_uart_console API: the interrupt-driven SCI8 RX/TX path is the subject under test, so it must own the channel's ISRs and registers itself. (The BSP is still linked – for LED1.)

Author: Brighton Sikarskie

Date: 2026-06-08

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

Since: 0.1.0

Definition in file main.c.

Enumeration Type Documentation

◆ uart_irq_config_t

enum uart_irq_config_t : uint32_t

Compile-time settings for the echo demo.

Enumerator
k_uart_irq_baud	UART IRQ baud.
k_uart_irq_loop_ms	UART IRQ loop ms.
k_uart_irq_sci_chan	Console channel: SCI8 (PD02/PD03).
k_uart_irq_isr_prio	NVIC priority for the SCI events.

Definition at line 60 of file main.c.

◆ uart_irq_event_t

enum uart_irq_event_t : uint16_t

SCI8 ELC event numbers (FSP ra8d2 bsp_elc: RXI/TXI/TEI).

Enumerator
k_uart_irq_event_rxi	SCI8 RXI receive-data-full event.
k_uart_irq_event_txi	SCI8 TXI transmit-data-empty event.
k_uart_irq_event_tei	SCI8 TEI transmit-end event.

Definition at line 68 of file main.c.

Function Documentation

◆ main()

void main ( void )

Application entry.

The application entry point Reset_Handler hands control to.

Brings up SCI8 + ISRs, prints, then echoes via IRQ.

Precondition: Reset_Handler has copied .data and zeroed .bss; SystemInit set VTOR/FPU.

Postcondition: On clean entry the CPU idles while the SCI ISRs echo received bytes.; On any HAL init failure the function halts in WFI.

Since: 0.1.0

Definition at line 294 of file main.c.

References k_uart_irq_banner, k_uart_irq_loop_ms, k_uart_irq_sci_chan, ra8_delay_ms(), ra8_isr_globals_enable(), ra8_sci_attach_rx_handler(), ra8_sci_read(), ra8_sci_write_polling(), s_uart_irq_rx_byte, uart_irq_panic_halt(), uart_irq_rx_cb(), and uart_irq_setup_or_halt().

◆ uart_irq_panic_halt()

void uart_irq_panic_halt ( void )

static

Halt forever in WFI – panic stop on any init failure.

Precondition: Called only after a fatal error in boot.

Postcondition: CPU is parked; only a debugger or external reset wakes it.

Since: 0.1.0

Definition at line 106 of file main.c.

Referenced by main(), and uart_irq_setup_or_halt().

◆ uart_irq_pins_init()

ra8_err_t uart_irq_pins_init ( void )

staticnodiscard

Route PD02 / PD03 to SCI8 TXD / RXD via the PFS PSEL field.

Returns: Error code from the first failing route call, or k_ra8_ok.

Return values

k_ra8_ok Both pins are SCI-routed.

Precondition: IOPORT module is reachable; single-threaded init context.

Postcondition: On success PD02 and PD03 are in SCI-async (PSEL=0x04) mode.

Since: 0.1.0

Definition at line 195 of file main.c.

References k_ra8_ok, k_ra8_psel_sci_async, k_uart_irq_pin_rxd, k_uart_irq_pin_txd, and ra8_pfs_route_peripheral().

Referenced by uart_irq_setup_or_halt().

◆ uart_irq_register_isrs()

ra8_err_t uart_irq_register_isrs ( void )

staticnodiscard

Register the SCI8 RXI / TXI / TEI events with the NVIC.

Returns: k_ra8_ok on success, else the first failing registration error.

Precondition: ra8_isr_init has run; interrupts not yet globally enabled.

Postcondition: Each SCI8 event links through IELSR and its NVIC line is enabled.

Since: 0.1.0

Definition at line 213 of file main.c.

References k_ra8_ok, k_uart_irq_event_rxi, k_uart_irq_event_tei, k_uart_irq_event_txi, k_uart_irq_isr_prio, ra8_isr_register(), uart_irq_rxi_isr(), uart_irq_tei_isr(), and uart_irq_txi_isr().

Referenced by uart_irq_setup_or_halt().

◆ uart_irq_rx_cb()

void uart_irq_rx_cb	(	void *	ctx,
		uint8_t	byte )

static

RX byte callback: echo the byte and re-arm the next receive.

Runs in RXI handler context (driver invokes it per received byte). Echoes the byte over the interrupt-driven transmitter (ra8_sci_write arms TIE, so the echo flows out through uart_irq_txi_isr) and re-arms a fresh 1-byte interrupt receive so the stream keeps draining.

Parameters

[in]	ctx	Unused callback context.
[in]	byte	The received data byte.

Returns: Nothing.

Since: 0.1.0

Definition at line 174 of file main.c.

References g_uart_irq_echoes, k_ra8_board_led1, k_uart_irq_sci_chan, ra8_board_led_toggle(), ra8_sci_read(), ra8_sci_write(), and s_uart_irq_rx_byte.

Referenced by main().

◆ uart_irq_rxi_isr()

void uart_irq_rxi_isr ( void * ctx )

static

SCI8 RXI ISR: drive the driver's receive state machine.

Parameters

[in] ctx Unused registration context.

Returns: Nothing.

Precondition: Registered for the SCI8 RXI event.

Postcondition: The driver has consumed one RDR byte and the RX callback has run.

Since: 0.1.0

Definition at line 124 of file main.c.

References k_uart_irq_sci_chan, and ra8_sci_dispatch_rxi().

Referenced by uart_irq_register_isrs().

◆ uart_irq_setup_or_halt()

void uart_irq_setup_or_halt ( void )

static

Bring CGC + SysTick + SCI8 + LED1 + the SCI ISRs up, or panic-halt.

Returns: Nothing (halts forever on any failure).

Since: 0.1.0

Definition at line 244 of file main.c.

References k_ra8_board_led1, k_ra8_clock_id_cpuclk0, k_ra8_clock_id_pclka, k_ra8_ok, k_ra8_sci_data_8, k_ra8_sci_parity_none, k_ra8_sci_stop_1, k_uart_irq_baud, k_uart_irq_sci_chan, ra8_board_led_init(), ra8_cgc_get_clock_hz(), ra8_cgc_init(), ra8_isr_init(), ra8_sci_init(), ra8_time_init(), uart_irq_panic_halt(), uart_irq_pins_init(), and uart_irq_register_isrs().

Referenced by main().

◆ uart_irq_tei_isr()

void uart_irq_tei_isr ( void * ctx )

static

SCI8 TEI ISR: end-of-transmission housekeeping.

Parameters

[in] ctx Unused registration context.

Returns: Nothing.

Precondition: Registered for the SCI8 TEI event.

Postcondition: The driver's error/end path has run for the channel.

Since: 0.1.0

Definition at line 154 of file main.c.

References k_uart_irq_sci_chan, and ra8_sci_dispatch_eri().

Referenced by uart_irq_register_isrs().

◆ uart_irq_txi_isr()

void uart_irq_txi_isr ( void * ctx )

static

SCI8 TXI ISR: push the next byte of an in-flight interrupt TX.

Parameters

[in] ctx Unused registration context.

Returns: Nothing.

Precondition: Registered for the SCI8 TXI event.

Postcondition: One queued TX byte has been written to TDR (or TIE cleared at end).

Since: 0.1.0

Definition at line 139 of file main.c.

References k_uart_irq_sci_chan, and ra8_sci_dispatch_txi().

Referenced by uart_irq_register_isrs().

Variable Documentation

◆ g_uart_irq_echoes

volatile uint32_t g_uart_irq_echoes = 0U

Count of bytes echoed from interrupt context.

Incremented only inside uart_irq_rx_cb (reached via the real RXI -> ra8_isr_dispatch -> driver path). A non-zero value is direct evidence the interrupt-driven receive ran; read externally by J-Link (HIL) and by tools/ra8_emulator (emulator).

Note: Read externally only; the firmware main loop never reads it back.

Since: 0.1.0

Definition at line 94 of file main.c.

Referenced by uart_irq_rx_cb().

◆ k_uart_irq_banner

const uint8_t k_uart_irq_banner[] = "uart_irq_echo ready\r\n"

static

Banner printed once over the polled path so the host sees a prompt.

Definition at line 79 of file main.c.

Referenced by main().

◆ k_uart_irq_pin_rxd

const ra8_port_pin_t k_uart_irq_pin_rxd = (ra8_port_pin_t)k_ra8_board_uart_console_pin_rxd

static

Definition at line 76 of file main.c.

Referenced by uart_irq_pins_init().

◆ k_uart_irq_pin_txd

const ra8_port_pin_t k_uart_irq_pin_txd = (ra8_port_pin_t)k_ra8_board_uart_console_pin_txd

static

Pinout for the on-board J-Link OB CDC channel (SCI8 / PD02 + PD03).

Definition at line 75 of file main.c.

Referenced by uart_irq_pins_init().

◆ s_uart_irq_rx_byte

uint8_t s_uart_irq_rx_byte

static

One-byte RX landing pad re-armed by every receive callback.

Definition at line 97 of file main.c.

Referenced by main(), and uart_irq_rx_cb().

Enumerations

Functions

Variables

Detailed Description

Enumeration Type Documentation

◆ uart_irq_config_t

◆ uart_irq_event_t

Function Documentation

◆ main()

◆ uart_irq_panic_halt()

◆ uart_irq_pins_init()

◆ uart_irq_register_isrs()

◆ uart_irq_rx_cb()

◆ uart_irq_rxi_isr()

◆ uart_irq_setup_or_halt()

◆ uart_irq_tei_isr()

◆ uart_irq_txi_isr()

Variable Documentation

◆ g_uart_irq_echoes

◆ k_uart_irq_banner

◆ k_uart_irq_pin_rxd

◆ k_uart_irq_pin_txd

◆ s_uart_irq_rx_byte