Writing to internal FLASH on Arduino

History

In LCD88 I use internal flash as storage for model definitions. Of course, these should be editable without reflashing all firmware:-)

On AVR chips writing to flash is only possible from bootloader section, so I needed such feature in my bootloader.
I adapted my old X-MODEM bootloader to provide some entry points to functions writing flash. But because of using X-MODEM as communication protocol, using it was quite difficult for ordinary people. Then, I came up with idea that bootloader compatible with Arduino could solve this accessibility issue.
Nowadays, all things that can be invented, are invented and done by some people, so I started to find ready-made bootloader with all needed features. Most promising was Optiboot, but it lacked possibility to use it for writing flash by application.

Time was passing by and I was very surprised that I can’t find ready-made solution. More surprising was that on Arduino forum writing to flash by application was perceived as ‘mission impossible’. Every topic about it ended by failure or with getting external memory for storage (flash, fram or simply SD card), or advice to write your own bootloader:-)

My conclusion after all this research was: I must write my own bootloader or contribute to some other project to add such functionality. Then I gave a first look at the code of Optiboot, it’s issues and I found issue #52 with one promising patch at the end. But this patch didn’t fit to my needs, as I need fill-erase-write sequence to not using RAM as buffer, and it doesn’t do that that way.

A year passed by and I returned to Optiboot. This time I was going to do it by mysef. It was time of learning C, hacks used in avr-gcc, bugs in different verions of avr-gcc, learning Github flows, branching, merging, even writing in Arduino as I needed to provide some working example of using this feature. But finally I made it! ­čÖé

Writing to flash

Optiboot with possibility to write to flash by applications could be downloaded from my ‘supermaster’ branch (also with some fixes not available yet in upstream): https://github.com/majekw/optiboot/tree/supermaster. It includes also example Arduino sketch (flash_program, heavily commented) writing to flash using new Optiboot.

So, feel free to use this long waited feature in Arduino world, and spread new, now better Optiboot bootloader.

This entry was posted in Electronics and tagged , , . Bookmark the permalink.

5 Responses to Writing to internal FLASH on Arduino

  1. kosmin says:

    Hello, first, good job for you work, I have used your library with example code writing to flash, but everything I do, only write a specific address. I tried (no so advanced programmer) to write flash to different address, and nothing. I’m experimenting on Atmega328 (Arduino) but failed. I want, at one command (timer, event …) to delete all flash (with bootloader or not). The demo code you provide only delete or write a specific page (I don’t know his address but I open hex file after writing to flash), no matter how I change the code. Please can you provide me a solution how to use your library to delete all flash, or at least, page, by page the flash from Atmega328.

    kosmin.dumitru (AT) gmail (dot) com

  2. uzi18 says:

    Da sie wykryc czy bootloader ma taka mozliwosc? Zalozylem issue w github.

    • majek says:

      Odpisa┼éem na githubie, ale w skr├│cie, to ja bym sprawdzi┼é najpierw rozmiar bootloadera czytaj─ůc odpowiednie ‘fusy’, je┼╝eli to b─Ödzie si─Ö zgadza─ç z Optibootem, to sprawdzi─ç pierwsze 2 s┼éowa bootloadera czy zawieraj─ů instrukcje ‘rjmp’. Wtedy jest du┼╝a szansa, ┼╝e to moja wersja Optiboota ­čÖé

  3. bemin Ghobreal says:

    hello majek,

    SO i am trying to use your concept to write to flash memory in my arduino micro. I’m trying to modfy the caterina bootloader and add the spm you have in the optiboot. but i keep get compiling error, any idea what could be the problem ?

    error is :

    /*
                 LUFA Library
         Copyright (C) Dean Camera, 2011.

      dean [at] fourwalledcubicle [dot] com
               www.lufa-lib.org
    */


    /*
      Copyright 2011  Dean Camera (dean [at] fourwalledcubicle [dot] com)

      Permission to use, copy, modify, distribute, and sell this
      software and its documentation for any purpose is hereby granted
      without fee, provided that the above copyright notice appear in
      all copies and that both that the copyright notice and this
      permission notice and warranty disclaimer appear in supporting
      documentation, and that the name of the author not be used in
      advertising or publicity pertaining to distribution of the
      software without specific, written prior permission.

      The author disclaim all warranties with regard to this
      software, including all implied warranties of merchantability
      and fitness.  In no event shall the author be liable for any
      special, indirect or consequential damages or any damages
      whatsoever resulting from loss of use, data or profits, whether
      in an action of contract, negligence or other tortious action,
      arising out of or in connection with the use or performance of
      this software.
    */


    /** \file
     *
     *  Main source file for the CDC class bootloader. This file contains the complete bootloader logic.
     */


    #define  INCLUDE_FROM_CATERINA_C
    #include "Caterina.h"
    //#include "Self_programming.h"


    #define CATERINA_MAJVER 4
    #define CATERINA_MINVER 4




    /** Contains the current baud rate and other settings of the first virtual serial port. This must be retained as some
     *  operating systems will not open the port unless the settings can be set successfully.
     */

    static CDC_LineEncoding_t LineEncoding = { .BaudRateBPS = 0,
                                               .CharFormat  = CDC_LINEENCODING_OneStopBit,
                                               .ParityType  = CDC_PARITY_None,
                                               .DataBits    = 8                            };

    /** Current address counter. This stores the current address of the FLASH or EEPROM as set by the host,
     *  and is used when reading or writing to the AVRs memory (either FLASH or EEPROM depending on the issued
     *  command.)
     */

    static uint32_t CurrAddress;

    /** Flag to indicate if the bootloader should be running, or should exit and allow the application code to run
     *  via a watchdog reset. When cleared the bootloader will exit, starting the watchdog and entering an infinite
     *  loop until the AVR restarts and the application runs.
     */

    static bool RunBootloader = true;

    /* Pulse generation counters to keep track of the time remaining for each pulse type */
    #define TX_RX_LED_PULSE_PERIOD 100
    uint16_t TxLEDPulse = 0; // time remaining for Tx LED pulse
    uint16_t RxLEDPulse = 0; // time remaining for Rx LED pulse

    /* Bootloader timeout timer */
    #define TIMEOUT_PERIOD  8000
    uint16_t Timeout = 0;

    uint16_t bootKey = 0x7777;
    volatile uint16_t *const bootKeyPtr = (volatile uint16_t *)0x0800;

    void StartSketch(void)
    {
        cli();
       
        /* Undo TIMER1 setup and clear the count before running the sketch */
        TIMSK1 = 0;
        TCCR1B = 0;
        TCNT1H = 0;     // 16-bit write to TCNT1 requires high byte be written first
        TCNT1L = 0;
       
        /* Relocate the interrupt vector table to the application section */
        MCUCR = (1 <> 8;
        if (p > 127)
            p = 254-p;
        p += p;
        if (((uint8_t)LLEDPulse) > p)
            L_LED_OFF();
        else
            L_LED_ON();
    }

    #if SPM_PAGESIZE > 255
    typedef uint16_t pagelen_t;
    #define GETLENGTH(len) len = getch() << 8 ; len |= getch()
    #else
    typedef uint8_t pagelen_t;
    #define GETLENGTH(len) (void) getch() ; len = get()
    #endif




    void pre_main(void) __attribute__ ((naked)) __attribute__ ((section (".init8")));
    static inline void writebuffer(int8_t memtype, uint8_t *mybuff,
                       uint16_t address, pagelen_t len);
    static inline void read_mem(uint8_t memtype, uint16_t address, pagelen_t len);
    static void __attribute__((noinline)) do_spm(uint16_t address, uint8_t command, uint16_t data);


    /* everything that needs to run VERY early */
    void pre_main(void) {
      // Allow convenient way of calling do_spm function - jump table,
      //   so entry to this function will always be here, indepedent of compilation,
      //   features etc
      __asm__ volatile (
        "  rjmp    1f\n"
        "  rjmp    do_spm\n"
        "1:\n"
      );
    }


    /** Main program entry point. This routine configures the hardware required by the bootloader, then continuously
     *  runs the bootloader processing routine until it times out or is instructed to exit.
     */

    int main(void)
    {
        /* Save the value of the boot key memory before it is overwritten */
        uint16_t bootKeyPtrVal = *bootKeyPtr;
        *bootKeyPtr = 0;

        /* Check the reason for the reset so we can act accordingly */
        uint8_t  mcusr_state = MCUSR;       // store the initial state of the Status register
        MCUSR = 0;                          // clear all reset flags   

        /* Watchdog may be configured with a 15 ms period so must disable it before going any further */
        wdt_disable();
       
        if (mcusr_state & (1<<EXTRF)) {
            // External reset -  we should continue to self-programming mode.
        } else if ((mcusr_state & (1<<PORF)) && (pgm_read_word(0) != 0xFFFF)) {      
            // After a power-on reset skip the bootloader and jump straight to sketch
            // if one exists.  
            StartSketch();
        } else if ((mcusr_state & (1< TIMEOUT_PERIOD)
                RunBootloader = false;

            LEDPulse();
        }

        /* Disconnect from the host - USB interface will be reset later along with the AVR */
        USB_Detach();

        /* Jump to beginning of application space to run the sketch - do not reset */  
        StartSketch();
    }

    /** Configures all hardware required for the bootloader. */
    void SetupHardware(void)
    {
        /* Disable watchdog if enabled by bootloader/fuses */
        MCUSR &= ~(1 << WDRF);
        wdt_disable();

        /* Disable clock division */
        clock_prescale_set(clock_div_1);

        /* Relocate the interrupt vector table to the bootloader section */
        MCUCR = (1 << IVCE);
        MCUCR = (1 << IVSEL);
       
        LED_SETUP();
        CPU_PRESCALE(0);
        L_LED_OFF();
        TX_LED_OFF();
        RX_LED_OFF();
       
        /* Initialize TIMER1 to handle bootloader timeout and LED tasks.  
         * With 16 MHz clock and 1/64 prescaler, timer 1 is clocked at 250 kHz
         * Our chosen compare match generates an interrupt every 1 ms.
         * This interrupt is disabled selectively when doing memory reading, erasing,
         * or writing since SPM has tight timing requirements.
         */

        OCR1AH = 0;
        OCR1AL = 250;
        TIMSK1 = (1 << OCIE1A);                   // enable timer 1 output compare A match interrupt
        TCCR1B = ((1 << CS11) | (1 << CS10));   // 1/64 prescaler on timer 1 input

        /* Initialize USB Subsystem */
        USB_Init();
    }

    //uint16_t ctr = 0;
    ISR(TIMER1_COMPA_vect, ISR_BLOCK)
    {
        /* Reset counter */
        TCNT1H = 0;
        TCNT1L = 0;

        /* Check whether the TX or RX LED one-shot period has elapsed.  if so, turn off the LED */
        if (TxLEDPulse && !(--TxLEDPulse))
            TX_LED_OFF();
        if (RxLEDPulse && !(--RxLEDPulse))
            RX_LED_OFF();
       
        if (pgm_read_word(0) != 0xFFFF)
            Timeout++;
    }

    /** Event handler for the USB_ConfigurationChanged event. This configures the device's endpoints ready
     *  to relay data to and from the attached USB host.
     */

    void EVENT_USB_Device_ConfigurationChanged(void)
    {
        /* Setup CDC Notification, Rx and Tx Endpoints */
        Endpoint_ConfigureEndpoint(CDC_NOTIFICATION_EPNUM, EP_TYPE_INTERRUPT,
                                   ENDPOINT_DIR_IN, CDC_NOTIFICATION_EPSIZE,
                                   ENDPOINT_BANK_SINGLE);

        Endpoint_ConfigureEndpoint(CDC_TX_EPNUM, EP_TYPE_BULK,
                                   ENDPOINT_DIR_IN, CDC_TXRX_EPSIZE,
                                   ENDPOINT_BANK_SINGLE);

        Endpoint_ConfigureEndpoint(CDC_RX_EPNUM, EP_TYPE_BULK,
                                   ENDPOINT_DIR_OUT, CDC_TXRX_EPSIZE,
                                   ENDPOINT_BANK_SINGLE);
    }

    /** Event handler for the USB_ControlRequest event. This is used to catch and process control requests sent to
     *  the device from the USB host before passing along unhandled control requests to the library for processing
     *  internally.
     */

    void EVENT_USB_Device_ControlRequest(void)
    {
        /* Ignore any requests that aren't directed to the CDC interface */
        if ((USB_ControlRequest.bmRequestType & (CONTROL_REQTYPE_TYPE | CONTROL_REQTYPE_RECIPIENT)) !=
            (REQTYPE_CLASS | REQREC_INTERFACE))
        {
            return;
        }

        /* Process CDC specific control requests */
        switch (USB_ControlRequest.bRequest)
        {
            case CDC_REQ_GetLineEncoding:
                if (USB_ControlRequest.bmRequestType == (REQDIR_DEVICETOHOST | REQTYPE_CLASS | REQREC_INTERFACE))
                {
                    Endpoint_ClearSETUP();

                    /* Write the line coding data to the control endpoint */
                    Endpoint_Write_Control_Stream_LE(&LineEncoding, sizeof(CDC_LineEncoding_t));
                    Endpoint_ClearOUT();
                }

                break;
            case CDC_REQ_SetLineEncoding:
                if (USB_ControlRequest.bmRequestType == (REQDIR_HOSTTODEVICE | REQTYPE_CLASS | REQREC_INTERFACE))
                {
                    Endpoint_ClearSETUP();

                    /* Read the line coding data in from the host into the global struct */
                    Endpoint_Read_Control_Stream_LE(&LineEncoding, sizeof(CDC_LineEncoding_t));
                    Endpoint_ClearIN();
                }

                break;
        }
    }

    #if !defined(NO_BLOCK_SUPPORT)
    /** Reads or writes a block of EEPROM or FLASH memory to or from the appropriate CDC data endpoint, depending
     *  on the AVR910 protocol command issued.
     *
     *  \param[in] Command  Single character AVR910 protocol command indicating what memory operation to perform
     */

    static void ReadWriteMemoryBlock(const uint8_t Command)
    {
        uint16_t BlockSize;
        char     MemoryType;

        bool     HighByte = false;
        uint8_t  LowByte  = 0;

        BlockSize  = (FetchNextCommandByte() < 0xFFFF)
                    WriteNextResponseByte(pgm_read_byte_far(CurrAddress | HighByte));
                    #else
                    WriteNextResponseByte(pgm_read_byte(CurrAddress | HighByte));
                    #endif

                    /* If both bytes in current word have been read, increment the address counter */
                    if (HighByte)
                      CurrAddress += 2;

                    HighByte = !HighByte;
                }
                else
                {
                    /* Read the next EEPROM byte into the endpoint */
                    WriteNextResponseByte(eeprom_read_byte((uint8_t*)(intptr_t)(CurrAddress >> 1)));

                    /* Increment the address counter after use */
                    CurrAddress += 2;
                }
            }
        }
        else
        {
            uint32_t PageStartAddress = CurrAddress;

            if (MemoryType == 'F')
            {
                boot_page_erase(PageStartAddress);
                boot_spm_busy_wait();
            }

            while (BlockSize--)
            {
                if (MemoryType == 'F')
                {
                    /* If both bytes in current word have been written, increment the address counter */
                    if (HighByte)
                    {
                        /* Write the next FLASH word to the current FLASH page */
                        boot_page_fill(CurrAddress, ((FetchNextCommandByte() <> 1)), FetchNextCommandByte());

                    /* Increment the address counter after use */
                    CurrAddress += 2;
                }
            }

            /* If in FLASH programming mode, commit the page after writing */
            if (MemoryType == 'F')
            {
                /* Commit the flash page to memory */
                boot_page_write(PageStartAddress);

                /* Wait until write operation has completed */
                boot_spm_busy_wait();
            }

            /* Send response byte back to the host */
            WriteNextResponseByte('\r');
        }

        /* Re-enable timer 1 interrupt disabled earlier in this routine */ 
        TIMSK1 = (1 << OCIE1A);
    }
    #endif

    /** Retrieves the next byte from the host in the CDC data OUT endpoint, and clears the endpoint bank if needed
     *  to allow reception of the next data packet from the host.
     *
     *  \return Next received byte from the host in the CDC data OUT endpoint
     */

    static uint8_t FetchNextCommandByte(void)
    {
        /* Select the OUT endpoint so that the next data byte can be read */
        Endpoint_SelectEndpoint(CDC_RX_EPNUM);

        /* If OUT endpoint empty, clear it and wait for the next packet from the host */
        while (!(Endpoint_IsReadWriteAllowed()))
        {
            Endpoint_ClearOUT();

            while (!(Endpoint_IsOUTReceived()))
            {
                if (USB_DeviceState == DEVICE_STATE_Unattached)
                  return 0;
            }
        }

        /* Fetch the next byte from the OUT endpoint */
        return Endpoint_Read_8();
    }

    /** Writes the next response byte to the CDC data IN endpoint, and sends the endpoint back if needed to free up the
     *  bank when full ready for the next byte in the packet to the host.
     *
     *  \param[in] Response  Next response byte to send to the host
     */

    static void WriteNextResponseByte(const uint8_t Response)
    {
        /* Select the IN endpoint so that the next data byte can be written */
        Endpoint_SelectEndpoint(CDC_TX_EPNUM);

        /* If IN endpoint full, clear it and wait until ready for the next packet to the host */
        if (!(Endpoint_IsReadWriteAllowed()))
        {
            Endpoint_ClearIN();

            while (!(Endpoint_IsINReady()))
            {
                if (USB_DeviceState == DEVICE_STATE_Unattached)
                  return;
            }
        }

        /* Write the next byte to the IN endpoint */
        Endpoint_Write_8(Response);
       
        TX_LED_ON();
        TxLEDPulse = TX_RX_LED_PULSE_PERIOD;
    }

    #define STK_OK              0x10
    #define STK_INSYNC          0x14  // ' '
    #define CRC_EOP             0x20  // 'SPACE'
    #define STK_GET_SYNC        0x30  // '0'

    #define STK_GET_PARAMETER   0x41  // 'A'
    #define STK_SET_DEVICE      0x42  // 'B'
    #define STK_SET_DEVICE_EXT  0x45  // 'E'
    #define STK_LOAD_ADDRESS    0x55  // 'U'
    #define STK_UNIVERSAL       0x56  // 'V'
    #define STK_PROG_PAGE       0x64  // 'd'
    #define STK_READ_PAGE       0x74  // 't'
    #define STK_READ_SIGN       0x75  // 'u'

    /** Task to read in AVR910 commands from the CDC data OUT endpoint, process them, perform the required actions
     *  and send the appropriate response back to the host.
     */

    void CDC_Task(void)
    {
        /* Select the OUT endpoint */
        Endpoint_SelectEndpoint(CDC_RX_EPNUM);

        /* Check if endpoint has a command in it sent from the host */
        if (!(Endpoint_IsOUTReceived()))
          return;
         
        RX_LED_ON();
        RxLEDPulse = TX_RX_LED_PULSE_PERIOD;

        /* Read in the bootloader command (first byte sent from host) */
        uint8_t Command = FetchNextCommandByte();

        if (Command == 'E')
        {
            /* We nearly run out the bootloader timeout clock,
            * leaving just a few hundred milliseconds so the
            * bootloder has time to respond and service any
            * subsequent requests */

            Timeout = TIMEOUT_PERIOD - 500;
       
            /* Re-enable RWW section - must be done here in case
             * user has disabled verification on upload.  */

            boot_rww_enable_safe();    

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 'T')
        {
            FetchNextCommandByte();

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if ((Command == 'L') || (Command == 'P'))
        {
            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 't')
        {
            // Return ATMEGA128 part code - this is only to allow AVRProg to use the bootloader
            WriteNextResponseByte(0x44);
            WriteNextResponseByte(0x00);
        }
        else if (Command == 'a')
        {
            // Indicate auto-address increment is supported
            WriteNextResponseByte('Y');
        }
        else if (Command == 'A')
        {
            // Set the current address to that given by the host
            CurrAddress   = (FetchNextCommandByte() << 9);
            CurrAddress  |= (FetchNextCommandByte() << 1);

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 'p')
        {
            // Indicate serial programmer back to the host
            WriteNextResponseByte('S');
        }
        else if (Command == 'S')
        {
            // Write the 7-byte software identifier to the endpoint
            for (uint8_t CurrByte = 0; CurrByte < 7; CurrByte++)
              WriteNextResponseByte(SOFTWARE_IDENTIFIER[CurrByte]);
        }
        else if (Command == 'V')
        {
            WriteNextResponseByte('0' + BOOTLOADER_VERSION_MAJOR);
            WriteNextResponseByte('0' + BOOTLOADER_VERSION_MINOR);
        }
        else if (Command == 's')
        {
            WriteNextResponseByte(AVR_SIGNATURE_3);
            WriteNextResponseByte(AVR_SIGNATURE_2);
            WriteNextResponseByte(AVR_SIGNATURE_1);
        }
        else if (Command == 'e')
        {
            // Clear the application section of flash
            for (uint32_t CurrFlashAddress = 0; CurrFlashAddress > 8);
            WriteNextResponseByte(SPM_PAGESIZE & 0xFF);
        }
        else if ((Command == 'B') || (Command == 'g'))
        {
            // Keep resetting the timeout counter if we're receiving self-programming instructions
            Timeout = 0;
            // Delegate the block write/read to a separate function for clarity
            ReadWriteMemoryBlock(Command);
        }
        #endif
        #if !defined(NO_FLASH_BYTE_SUPPORT)
        else if (Command == 'C')
        {
            // Write the high byte to the current flash page
            boot_page_fill(CurrAddress, FetchNextCommandByte());

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 'c')
        {
            // Write the low byte to the current flash page
            boot_page_fill(CurrAddress | 0x01, FetchNextCommandByte());

            // Increment the address
            CurrAddress += 2;

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 'm')
        {
            // Commit the flash page to memory
            boot_page_write(CurrAddress);

            // Wait until write operation has completed
            boot_spm_busy_wait();

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 'R')
        {
            #if (FLASHEND > 0xFFFF)
            uint16_t ProgramWord = pgm_read_word_far(CurrAddress);
            #else
            uint16_t ProgramWord = pgm_read_word(CurrAddress);
            #endif

            WriteNextResponseByte(ProgramWord >> 8);
            WriteNextResponseByte(ProgramWord & 0xFF);
        }
        #endif
        #if !defined(NO_EEPROM_BYTE_SUPPORT)
        else if (Command == 'D')
        {
            // Read the byte from the endpoint and write it to the EEPROM
            eeprom_write_byte((uint8_t*)((intptr_t)(CurrAddress >> 1)), FetchNextCommandByte());

            // Increment the address after use
            CurrAddress += 2;

            // Send confirmation byte back to the host
            WriteNextResponseByte('\r');
        }
        else if (Command == 'd')
        {
            // Read the EEPROM byte and write it to the endpoint
            WriteNextResponseByte(eeprom_read_byte((uint8_t*)((intptr_t)(CurrAddress >> 1))));

            // Increment the address after use
            CurrAddress += 2;
        }
        #endif
        else if (Command != 27)
        {
            // Unknown (non-sync) command, return fail code
            WriteNextResponseByte('?');
        }
       

        /* Select the IN endpoint */
        Endpoint_SelectEndpoint(CDC_TX_EPNUM);

        /* Remember if the endpoint is completely full before clearing it */
        bool IsEndpointFull = !(Endpoint_IsReadWriteAllowed());

        /* Send the endpoint data to the host */
        Endpoint_ClearIN();

        /* If a full endpoint's worth of data was sent, we need to send an empty packet afterwards to signal end of transfer */
        if (IsEndpointFull)
        {
            while (!(Endpoint_IsINReady()))
            {
                if (USB_DeviceState == DEVICE_STATE_Unattached)
                  return;
            }

            Endpoint_ClearIN();
        }

        /* Wait until the data has been sent to the host */
        while (!(Endpoint_IsINReady()))
        {
            if (USB_DeviceState == DEVICE_STATE_Unattached)
              return;
        }

        /* Select the OUT endpoint */
        Endpoint_SelectEndpoint(CDC_RX_EPNUM);

        /* Acknowledge the command from the host */
        Endpoint_ClearOUT();
    }
    /* Write to flash memory




    /*
     * void writebuffer(memtype, buffer, address, length)
     */

    static inline void writebuffer(int8_t memtype, uint8_t *mybuff,
                       uint16_t address, pagelen_t len)
    {
        switch (memtype) {
        case 'E': // EEPROM
    #if defined(SUPPORT_EEPROM) || defined(BIGBOOT)
            while(len--) {
            eeprom_write_byte((uint8_t *)(address++), *mybuff++);
            }
    #else
        /*
         * On systems where EEPROM write is not supported, just busy-loop
         * until the WDT expires, which will eventually cause an error on
         * host system (which is what it should do.)
         */

        while (1)
            ; // Error: wait for WDT
    #endif
        break;
        default:  // FLASH
        /*
         * Default to writing to Flash program memory.  By making this
         * the default rather than checking for the correct code, we save
         * space on chips that don't support any other memory types.
         */

        {
            // Copy buffer into programming buffer
            uint8_t *bufPtr = mybuff;
            uint16_t addrPtr = (uint16_t)(void*)address;

            /*
             * Start the page erase and wait for it to finish.  There
             * used to be code to do this while receiving the data over
             * the serial link, but the performance improvement was slight,
             * and we needed the space back.
             */

            do_spm((uint16_t)(void*)address,__BOOT_PAGE_ERASE,0);

            /*
             * Copy data from the buffer into the flash write buffer.
             */

            do {
            uint16_t a;
            a = *bufPtr++;
            a |= (*bufPtr++) << 8;
            do_spm((uint16_t)(void*)addrPtr,__BOOT_PAGE_FILL,a);
            addrPtr += 2;
            } while (len -= 2);

            /*
             * Actually Write the buffer to flash (and wait for it to finish.)
             */

            do_spm((uint16_t)(void*)address,__BOOT_PAGE_WRITE,0);
        } // default block
        break;
        } // switch
    }

    static inline void read_mem(uint8_t memtype, uint16_t address, pagelen_t length)
    {
        uint8_t ch;

        switch (memtype) {

    #if defined(SUPPORT_EEPROM) || defined(BIGBOOT)
        case 'E': // EEPROM
        do {
            putch(eeprom_read_byte((uint8_t *)(address++)));
        } while (--length);
        break;
    #endif
        default:
        do {
    #ifdef VIRTUAL_BOOT_PARTITION
            // Undo vector patch in bottom page so verify passes
            if (address == rstVect0) ch = rstVect0_sav;
            else if (address == rstVect1) ch = rstVect1_sav;
            else if (address == saveVect0) ch = saveVect0_sav;
            else if (address == saveVect1) ch = saveVect1_sav;
            else ch = pgm_read_byte_near(address);
            address++;
    #elif defined(RAMPZ)
            // Since RAMPZ should already be set, we need to use EPLM directly.
            // Also, we can use the autoincrement version of lpm to update "address"
            //      do putch(pgm_read_byte_near(address++));
            //      while (--length);
            // read a Flash and increment the address (may increment RAMPZ)
            __asm__ ("elpm %0,Z+\n" : "=r" (ch), "=z" (address): "1" (address));
    #else
            // read a Flash byte and increment the address
            __asm__ ("lpm %0,Z+\n" : "=r" (ch), "=z" (address): "1" (address));
    #endif
            putch(ch);
        } while (--length);
        break;
        } // switch
    }

    /*
     * Separate function for doing spm stuff
     * It's needed for application to do SPM, as SPM instruction works only
     * from bootloader.
     *
     * How it works:
     * - do SPM
     * - wait for SPM to complete
     * - if chip have RWW/NRWW sections it does additionaly:
     *   - if command is WRITE or ERASE, AND data=0 then reenable RWW section
     *
     * In short:
     * If you play erase-fill-write, just set data to 0 in ERASE and WRITE
     * If you are brave, you have your code just below bootloader in NRWW section
     *   you could do fill-erase-write sequence with data!=0 in ERASE and
     *   data=0 in WRITE
     */

    static void do_spm(uint16_t address, uint8_t command, uint16_t data) {
        // Do spm stuff
        asm volatile (
        "    movw  r0, %3\n"
            "    out %0, %1\n"
            "    spm\n"
            "    clr  r1\n"
            :
            : "i" (_SFR_IO_ADDR(__SPM_REG)),
              "r" ((uint8_t)command),
              "z" ((uint16_t)address),
              "r" ((uint16_t)data)
            : "r0"
        );

        // wait for spm to complete
        //   it doesn't have much sense for __BOOT_PAGE_FILL,
        //   but it doesn't hurt and saves some bytes on 'if'
        boot_spm_busy_wait();
    #if defined(RWWSRE)
        // this 'if' condition should be: (command == __BOOT_PAGE_WRITE || command == __BOOT_PAGE_ERASE)...
        // but it's tweaked a little assuming that in every command we are interested in here, there
        // must be also SELFPRGEN set. If we skip checking this bit, we save here 4B
        if ((command & (_BV(PGWRT)|_BV(PGERS))) && (data == 0) ) {
          // Reenable read access to flash
          boot_rww_enable();
        }
    #endif
    }

Leave a Reply

Your email address will not be published. Required fields are marked *