SNC7330 bootrom console over UART1

README.md

This code executes the SNC7330 bootrom built-in console standalone and uses UART1 instead of UART0 for I/O.

To build, use the SN_M3B SDK with default startup code to do some basic setup, and use this code for your main program. Add symbol mapping as necessary.

Auto-baud rate is enabled, so connect with any baud rate (115200 by default). Hit escape at start of line to have the console emit some newlines, and type ? to see commands. Be careful while working with the console, because it is capable of erasing flash.

main.c

#include <stdlib.h>

#include "snc_drv.h"

// FPB registers
#define FP_CTRL        *((volatile unsigned int *)0xe0002000)
#define FP_REMAP       *((volatile unsigned int *)0xe0002004)
#define FP_COMPn       ((volatile unsigned int *)0xe0002008)

extern uint32_t remap_table[2]; // 0x20000180

// ROM structs
typedef struct {
    void (*write_fn)(uint8_t ch);
    uint8_t (*read_fn)(void);
} xmodem_callbacks_t;

// ROM variables
extern volatile uint32_t systick; // 0x18018434
extern uint32_t uart_console_proc_index; // 0x180185b8
extern uint32_t uart_console_print_greeting; // 0x180185bc

// ROM functions
extern int uart_init(SN_UART_Type *pDev, uint32_t sys_clock, uint32_t baud_rate); // 0x0800c3b8
extern int uart_console_procedure(void); // 0x08005b5c
extern void uart_console_xmodem_set_cb(xmodem_callbacks_t *cb); // 0x08004798
extern int UART_WriteByte(uart_port_t port_id, uint8_t data); // 0x08003604
extern uint32_t UART_ReadByte(uart_port_t port_id); // 0x080035c8
extern void UART_IRQ_Handler_ROM(SN_UART_Type *huart, uint32_t uart_index); // 0x08004b90

static void platform_init(void);
static void patch_rom(void);
static void uart_console_init(void);

int main(void) {
    platform_init();
    
    patch_rom();
    SN_SYS1->PCLK_EN_b.UARTCLKEN = 1;
    SN_SYS1->PCLK_RST_b.UARTRST = 1;
    while (SN_SYS1->PCLK_RST_b.UARTRST);
    uart_console_init();
    uart_console_proc_index = 0;
    uart_console_print_greeting = 1;
    NVIC_EnableIRQ(UART1_IRQn);
    for (;;) {
        uart_console_procedure();
    }

    return 0; // Should never be reached
}

static void patch_rom(void)
{
    // Setup remap table
    // Patch UART_WriteByte() and UART_WriteMultiBytes() to use SN_UART1 for port_id == UART_PORT_0

    // 0800360c: ldr.eq r0,[0x08003638]
    // 0800360e: beq 0x08003618
    remap_table[0] = 0xd003480a;
    // 0800d548: ldr.eq r0,[0x0800d584]
    // 0800d54a: beq 0x0800d554
    remap_table[1] = 0xd003480e;

    // Configure FPB
    FP_REMAP = (unsigned int)&remap_table & 0x1FFFFFE0;
    FP_COMPn[0] = 0x0800360c | 1; // REPLACE=0, ENABLE=1
    FP_COMPn[1] = 0x0800d548 | 1;
    FP_CTRL |= 3; // KEY=1, ENABLE=1
}

void uart_write_char(uint8_t ch)
{
    UART_WriteByte(UART_PORT_1, ch);
}

uint8_t uart_read_char(void)
{
    return UART_ReadByte(UART_PORT_1);
}

static void uart_console_init(void)
{
    // Everything is UART1
    xmodem_callbacks_t cb = {
        .write_fn = uart_write_char,
        .read_fn = uart_read_char,
    };

    uart_console_xmodem_set_cb(&cb);
    uart_init(SN_UART1, System_Get_SysClk(), 115200);
    SN_UART1->IE_b.ABEOIE = 1;
    SN_UART1->ABCTRL_b.MODE = 1;
    SN_UART1->ABCTRL_b.START = 1;
}

static void platform_init(void)
{
    systick = 0;
    SysTick_Config(System_Get_SysClk() / 1000);
}

void SysTick_Handler(void)
{
    ++systick;
}

void UART1_IRQHandler(void)
{
    UART_IRQ_Handler_ROM(SN_UART1, 1);
}