VersaMCU/bootloader/src/main.c

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 *         SAM Software Package License
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 * Copyright (c) 2011-2014, Atmel Corporation
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/**
 * --------------------
 * SAM-BA Implementation on SAMD21
 * --------------------
 * Requirements to use SAM-BA :
 *
 * Supported communication interfaces :
 * --------------------
 *
 * SERCOM5 : RX:PB23 TX:PB22
 * Baudrate : 115200 8N1
 *
 * USB : D-:PA24 D+:PA25
 *
 * Pins Usage
 * --------------------
 * The following pins are used by the program :
 * PA25 : input/output
 * PA24 : input/output
 * PB23 : input
 * PB22 : output
 * PA15 : input
 *
 * The application board shall avoid driving the PA25,PA24,PB23,PB22 and PA15
 * signals
 * while the boot program is running (after a POR for example)
 *
 * Clock system
 * --------------------
 * CPU clock source (GCLK_GEN_0) - 8MHz internal oscillator (OSC8M)
 * SERCOM5 core GCLK source (GCLK_ID_SERCOM5_CORE) - GCLK_GEN_0 (i.e., OSC8M)
 * GCLK Generator 1 source (GCLK_GEN_1) - 48MHz DFLL in Clock Recovery mode
 * (DFLL48M)
 * USB GCLK source (GCLK_ID_USB) - GCLK_GEN_1 (i.e., DFLL in CRM mode)
 *
 * Memory Mapping
 * --------------------
 * SAM-BA code will be located at 0x0 and executed before any applicative code.
 *
 * Applications compiled to be executed along with the bootloader will start at
 * 0x2000 (samd21) or 0x4000 (samd51)
 * The bootloader doesn't changes the VTOR register, application code is 
 * taking care of this.
 *
 */

#include "uf2.h"

static void check_start_application(void);

static volatile bool main_b_cdc_enable = false;
extern int8_t led_tick_step;

#ifdef SAMD21
#define RESET_CONTROLLER PM
#endif
#ifdef SAMD51
#define RESET_CONTROLLER RSTC
#endif

#if defined(BOOT_KEY_ROW_PIN) && defined(BOOT_KEY_COL_PIN)
/**
 * \brief Check whether the boot-hold key (bottom-right Cherry MX button) is
 * held down. Drives its matrix row low and reads its matrix column back,
 * the same polarity the app firmware's own matrix scan uses.
 */
static bool boot_key_pressed(void) {
    PORT_PINCFG_Type col_cfg = {0};
    col_cfg.bit.PMUXEN = false;
    col_cfg.bit.INEN   = true; // external 10k pull-up already on the board

    PORT_PINCFG_Type row_cfg = {0};
    row_cfg.bit.PMUXEN = false;
    row_cfg.bit.DRVSTR = true;

    PINCFG(BOOT_KEY_COL_PIN) = col_cfg.reg;
    PINOP(BOOT_KEY_COL_PIN, DIRCLR); // column stays an input

    PINOP(BOOT_KEY_ROW_PIN, OUTCLR); // pre-set drive level before enabling output
    PINCFG(BOOT_KEY_ROW_PIN) = row_cfg.reg;
    PINOP(BOOT_KEY_ROW_PIN, DIRSET); // row -> output, driving low

    for (volatile int i = 0; i < 200; i++) {
    } // let the row settle through the diode/pull-up RC

    bool pressed = (PINIP(BOOT_KEY_COL_PIN) == 0);

    PINOP(BOOT_KEY_ROW_PIN, DIRCLR); // release row back to high-Z
    return pressed;
}
#endif

/**
 * \brief Check the application startup condition
 *
 */
static void check_start_application(void) {
    uint32_t app_start_address;

#if defined(BOOT_KEY_ROW_PIN) && defined(BOOT_KEY_COL_PIN)
    if (boot_key_pressed()) {
        /* Stay in bootloader */
        return;
    }
#endif

// Check if there is an IO which will hold us inside the bootloader.
#if defined(HOLD_PIN) && defined(HOLD_STATE)
    PORT_PINCFG_Type pincfg = {0};
    pincfg.bit.PMUXEN = false;
    pincfg.bit.INEN   = true;
    pincfg.bit.DRVSTR = true;
    
    PINOP(HOLD_PIN, DIRCLR);        // Pin is an input

  #if defined(HOLD_PIN_PULLUP)
    pincfg.bit.PULLEN = true;
    PINOP(HOLD_PIN, OUTSET); // Pin is pulled up.
  #elif defined(HOLD_PIN_PULLDOWN)
    pincfg.bit.PULLEN = true;
    PINOP(HOLD_PIN, OUTCLR); // Pin is pulled up.
  #endif
    PINCFG(HOLD_PIN) = pincfg.reg;

    if (PINIP(HOLD_PIN) == HOLD_STATE) {
        /* Stay in bootloader */
        return;
    }
#endif

    /* Load the Reset Handler address of the application */
    app_start_address = *(uint32_t *)(APP_START_ADDRESS + 4);

    /**
     * Test reset vector of application @APP_START_ADDRESS+4
     * Sanity check on the Reset_Handler address
     */
    if (app_start_address < APP_START_ADDRESS || app_start_address > FLASH_SIZE) {
        /* Stay in bootloader */
        return;
    }

#if USE_SINGLE_RESET
    if (SINGLE_RESET()) {
        if (RESET_CONTROLLER->RCAUSE.bit.POR || *DBL_TAP_PTR != DBL_TAP_MAGIC_QUICK_BOOT) {
            // the second tap on reset will go into app
            *DBL_TAP_PTR = DBL_TAP_MAGIC_QUICK_BOOT;
            // this will be cleared after succesful USB enumeration
            // this is around 1.5s
            resetHorizon = timerHigh + 50;
            return;
        }
    }
#endif

    if (RESET_CONTROLLER->RCAUSE.bit.POR) {
        *DBL_TAP_PTR = 0;
    } else if (*DBL_TAP_PTR == DBL_TAP_MAGIC) {
        *DBL_TAP_PTR = 0;
        return; // stay in bootloader
    } else {
        if (*DBL_TAP_PTR != DBL_TAP_MAGIC_QUICK_BOOT) {
            *DBL_TAP_PTR = DBL_TAP_MAGIC;
            delay(500);
        }
        *DBL_TAP_PTR = 0;
    }

    LED_MSC_OFF();
#if defined(__SAMD21E18A__)
    RGBLED_set_color(COLOR_LEAVE);
#endif

    /* Rebase the Stack Pointer */
    __set_MSP(*(uint32_t *)APP_START_ADDRESS);

    /* Rebase the vector table base address */
    SCB->VTOR = ((uint32_t)APP_START_ADDRESS & SCB_VTOR_TBLOFF_Msk);

    /* Ensure the MSP/VTOR writes are visible before jumping; without these
     * barriers the app's first fetch can race the pipeline (observed on
     * real hardware: identical MSP/VTOR/PC values injected by a halted
     * debugger boot fine, but the bootloader's own running jump hard-faults
     * every time). */
    __DSB();
    __ISB();

    /* Jump to application Reset Handler in the application */
    asm("bx %0" ::"r"(app_start_address));
}

extern char _etext;
extern char _end;

/**
 *  \brief SAMD21 SAM-BA Main loop.
 *  \return Unused (ANSI-C compatibility).
 */
int main(void) {
    // if VTOR is set, we're not running in bootloader mode; halt
    if (SCB->VTOR)
        while (1) {
        }

#if (USB_VID == 0x239a) && (USB_PID == 0x0013) // Adafruit Metro M0
    // Delay a bit so SWD programmer can have time to attach.
    delay(15);
#endif
    led_init();

    logmsg("Start");
    assert((uint32_t)&_etext < APP_START_ADDRESS);
    // bossac writes at 0x20005000
    assert(!USE_MONITOR || (uint32_t)&_end < 0x20005000);

    assert(8 << NVMCTRL->PARAM.bit.PSZ == FLASH_PAGE_SIZE);
    assert(FLASH_PAGE_SIZE * NVMCTRL->PARAM.bit.NVMP == FLASH_SIZE);

    /* Jump in application if condition is satisfied */
    check_start_application();

    /* We have determined we should stay in the monitor. */
    /* System initialization */
    system_init();

    __DMB();
    __enable_irq();

#if USE_UART
    /* UART is enabled in all cases */
    usart_open();
#endif

    logmsg("Before main loop");

    usb_init();

    // not enumerated yet
    RGBLED_set_color(COLOR_START);
    led_tick_step = 10;

    /* Wait for a complete enum on usb or a '#' char on serial line */
    while (1) {
        if (USB_Ok()) {
            if (!main_b_cdc_enable) {
#if USE_SINGLE_RESET
                // this might have been set
                resetHorizon = 0;
#endif
                RGBLED_set_color(COLOR_USB);
                led_tick_step = 1;

#if USE_SCREEN
                screen_init();
                draw_drag();
#endif
            }

            main_b_cdc_enable = true;
        }

#if USE_MONITOR
        // Check if a USB enumeration has succeeded
        // And com port was opened
        if (main_b_cdc_enable) {
            logmsg("entering monitor loop");
            // SAM-BA on USB loop
            while (1) {
                sam_ba_monitor_run();
            }
        }
#if USE_UART
        /* Check if a '#' has been received */
        if (!main_b_cdc_enable && usart_sharp_received()) {
            RGBLED_set_color(COLOR_UART);
            sam_ba_monitor_init(SAM_BA_INTERFACE_USART);
            /* SAM-BA on UART loop */
            while (1) {
                sam_ba_monitor_run();
            }
        }
#endif
#else // no monitor
        if (main_b_cdc_enable) {
            process_msc();
        }
#endif

        if (!main_b_cdc_enable) {
            // get more predictable timings before the USB is enumerated
            for (int i = 1; i < 256; ++i) {
                asm("nop");
            }
        }
    }
}