Implement a virtual bootloader section
- patch reset vector while programming flash page0 Let the reset vector always point to the twiboot start. - Use another (must be unused!) ISR vector to store the original reset vector as jump to the application. - Cache the values for the verification read - currently works only for devices < 8kB flash (2 byte vector entries) - using a attiny85 as target This change is heavily based on the optiboot bootloader.
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2
Makefile
2
Makefile
@ -67,7 +67,7 @@ AVRDUDE_MCU=t85
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AVRDUDE_FUSES=lfuse:w:0xe2:m hfuse:w:0xdd:m efuse:w:0xfe:m
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BOOTLOADER_START=0x1C00
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CFLAGS_TARGET=-DUSE_CLOCKSTRETCH=1
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CFLAGS_TARGET=-DUSE_CLOCKSTRETCH=1 -DVIRTUAL_BOOT_SECTION=1
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endif
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# ---------------------------------------------------------------------------
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92
main.c
92
main.c
@ -29,6 +29,10 @@
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#define USE_CLOCKSTRETCH 0
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#endif
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#ifndef VIRTUAL_BOOT_SECTION
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#define VIRTUAL_BOOT_SECTION 0
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#endif
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#ifndef TWI_ADDRESS
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#define TWI_ADDRESS 0x29
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#endif
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@ -86,6 +90,23 @@
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#define USI_ENABLE_SCL_HOLD 0x40 /* Hold SCL low after clock overflow */
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#endif /* !defined(TWCR) && defined(USICR) */
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#if (VIRTUAL_BOOT_SECTION)
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/* unused vector to store application start address */
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#define APPVECT_NUM EE_RDY_vect_num
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/* each vector table entry is a 2byte RJMP opcode */
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#define RSTVECT_ADDR 0x0000
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#define APPVECT_ADDR (APPVECT_NUM * 2)
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#define RSTVECT_PAGE_OFFSET (RSTVECT_ADDR % SPM_PAGESIZE)
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#define APPVECT_PAGE_OFFSET (APPVECT_ADDR % SPM_PAGESIZE)
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/* create RJMP opcode for the vector table */
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#define OPCODE_RJMP(addr) (((addr) & 0x0FFF) | 0xC000)
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#elif (!defined(ASRE) && !defined (RWWSRE))
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#error "Device without bootloader section requires VIRTUAL_BOOT_SECTION"
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#endif
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/* SLA+R */
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#define CMD_WAIT 0x00
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#define CMD_READ_VERSION 0x01
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@ -165,6 +186,12 @@ static uint8_t cmd = CMD_WAIT;
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static uint8_t buf[SPM_PAGESIZE];
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static uint16_t addr;
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#if (VIRTUAL_BOOT_SECTION)
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/* reset/application vectors received from host, needed for verify read */
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static uint8_t rstvect_save[2];
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static uint8_t appvect_save[2];
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#endif /* (VIRTUAL_BOOT_SECTION) */
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/* *************************************************************************
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* write_flash_page
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* ************************************************************************* */
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@ -174,6 +201,29 @@ static void write_flash_page(void)
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uint8_t size = SPM_PAGESIZE;
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uint8_t *p = buf;
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#if (VIRTUAL_BOOT_SECTION)
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if (pagestart == (RSTVECT_ADDR & ~(SPM_PAGESIZE -1)))
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{
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/* save original vectors for verify read */
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rstvect_save[0] = buf[RSTVECT_PAGE_OFFSET];
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rstvect_save[1] = buf[RSTVECT_PAGE_OFFSET + 1];
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appvect_save[0] = buf[APPVECT_PAGE_OFFSET];
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appvect_save[1] = buf[APPVECT_PAGE_OFFSET + 1];
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/* replace reset vector with jump to bootloader address */
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uint16_t rst_vector = OPCODE_RJMP(BOOTLOADER_START -1);
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buf[RSTVECT_PAGE_OFFSET] = (rst_vector & 0xFF);
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buf[RSTVECT_PAGE_OFFSET + 1] = (rst_vector >> 8) & 0xFF;
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/* replace application vector with jump to original reset vector */
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uint16_t app_vector = rstvect_save[0] | (rstvect_save[1] << 8);
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app_vector = OPCODE_RJMP(app_vector - APPVECT_NUM);
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buf[APPVECT_PAGE_OFFSET] = (app_vector & 0xFF);
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buf[APPVECT_PAGE_OFFSET + 1] = (app_vector >> 8) & 0xFF;
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}
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#endif /* (VIRTUAL_BOOT_SECTION) */
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if (pagestart < BOOTLOADER_START)
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{
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boot_page_erase(pagestart);
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@ -399,7 +449,33 @@ static uint8_t TWI_data_read(uint8_t bcnt)
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break;
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case CMD_ACCESS_FLASH:
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data = pgm_read_byte_near(addr++);
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switch (addr)
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{
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/* return cached values for verify read */
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#if (VIRTUAL_BOOT_SECTION)
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case RSTVECT_ADDR:
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data = rstvect_save[0];
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break;
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case (RSTVECT_ADDR + 1):
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data = rstvect_save[1];
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break;
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case APPVECT_ADDR:
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data = appvect_save[0];
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break;
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case (APPVECT_ADDR + 1):
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data = appvect_save[1];
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break;
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#endif /* (VIRTUAL_BOOT_SECTION) */
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default:
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data = pgm_read_byte_near(addr);
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break;
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}
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addr++;
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break;
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#if (EEPROM_SUPPORT)
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@ -680,7 +756,11 @@ static void TIMER0_OVF_vect(void)
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} /* TIMER0_OVF_vect */
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static void (*jump_to_app)(void) __attribute__ ((noreturn)) = 0x0000;
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#if (VIRTUAL_BOOT_SECTION)
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static void (*jump_to_app)(void) __attribute__ ((noreturn)) = (void*)APPVECT_ADDR;
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#else
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static void (*jump_to_app)(void) __attribute__ ((noreturn)) = (void*)0x0000;
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#endif
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/* *************************************************************************
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@ -731,6 +811,14 @@ int main(void)
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LED_INIT();
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LED_GN_ON();
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#if (VIRTUAL_BOOT_SECTION)
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/* load current values (for reading flash) */
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rstvect_save[0] = pgm_read_byte_near(RSTVECT_ADDR);
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rstvect_save[1] = pgm_read_byte_near(RSTVECT_ADDR + 1);
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appvect_save[0] = pgm_read_byte_near(APPVECT_ADDR);
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appvect_save[1] = pgm_read_byte_near(APPVECT_ADDR + 1);
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#endif /* (VIRTUAL_BOOT_SECTION) */
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/* timer0: running with F_CPU/1024 */
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#if defined (TCCR0)
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TCCR0 = (1<<CS02) | (1<<CS00);
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