A TWI / I2C bootloader for AVR MCUs
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/***************************************************************************
* Copyright (C) 10/2020 by Olaf Rempel *
* razzor@kopf-tisch.de *
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; version 2 of the License, *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License for more details. *
* *
* You should have received a copy of the GNU General Public License *
* along with this program; if not, write to the *
* Free Software Foundation, Inc., *
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
***************************************************************************/
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/boot.h>
#include <avr/pgmspace.h>
#define VERSION_STRING "TWIBOOT v3.1"
#define EEPROM_SUPPORT 1
#define LED_SUPPORT 1
#ifndef USE_CLOCKSTRETCH
#define USE_CLOCKSTRETCH 0
#endif
#ifndef VIRTUAL_BOOT_SECTION
#define VIRTUAL_BOOT_SECTION 0
#endif
#ifndef TWI_ADDRESS
#define TWI_ADDRESS 0x29
#endif
#define F_CPU 8000000ULL
#define TIMER_DIVISOR 1024
#define TIMER_IRQFREQ_MS 25
#define TIMEOUT_MS 1000
#define TIMER_MSEC2TICKS(x) ((x * F_CPU) / (TIMER_DIVISOR * 1000ULL))
#define TIMER_MSEC2IRQCNT(x) (x / TIMER_IRQFREQ_MS)
#if (LED_SUPPORT)
#define LED_INIT() DDRB = ((1<<PORTB4) | (1<<PORTB5))
#define LED_RT_ON() PORTB |= (1<<PORTB4)
#define LED_RT_OFF() PORTB &= ~(1<<PORTB4)
#define LED_GN_ON() PORTB |= (1<<PORTB5)
#define LED_GN_OFF() PORTB &= ~(1<<PORTB5)
#define LED_GN_TOGGLE() PORTB ^= (1<<PORTB5)
#define LED_OFF() PORTB = 0x00
#else
#define LED_INIT()
#define LED_RT_ON()
#define LED_RT_OFF()
#define LED_GN_ON()
#define LED_GN_OFF()
#define LED_GN_TOGGLE()
#define LED_OFF()
#endif /* LED_SUPPORT */
#if !defined(TWCR) && defined(USICR)
#define USI_PIN_INIT() { PORTB |= ((1<<PORTB0) | (1<<PORTB2)); \
DDRB |= (1<<PORTB2); \
}
#define USI_PIN_SDA_INPUT() DDRB &= ~(1<<PORTB0)
#define USI_PIN_SDA_OUTPUT() DDRB |= (1<<PORTB0)
#define USI_PIN_SCL() (PINB & (1<<PINB2))
#if (USE_CLOCKSTRETCH == 0)
#error "USI peripheral requires enabled USE_CLOCKSTRETCH"
#endif
#define USI_STATE_MASK 0x0F
#define USI_STATE_IDLE 0x00 /* wait for Start Condition */
#define USI_STATE_SLA 0x01 /* wait for Slave Address */
#define USI_STATE_SLAW_ACK 0x02 /* ACK Slave Address + Write (Master writes) */
#define USI_STATE_SLAR_ACK 0x03 /* ACK Slave Address + Read (Master reads) */
#define USI_STATE_NAK 0x04 /* send NAK */
#define USI_STATE_DATW 0x05 /* receive Data */
#define USI_STATE_DATW_ACK 0x06 /* transmit ACK for received Data */
#define USI_STATE_DATR 0x07 /* transmit Data */
#define USI_STATE_DATR_ACK 0x08 /* receive ACK for transmitted Data */
#define USI_WAIT_FOR_ACK 0x10 /* wait for ACK bit (2 SCL clock edges) */
#define USI_ENABLE_SDA_OUTPUT 0x20 /* SDA is output (slave transmitting) */
#define USI_ENABLE_SCL_HOLD 0x40 /* Hold SCL low after clock overflow */
#endif /* !defined(TWCR) && defined(USICR) */
#if (VIRTUAL_BOOT_SECTION)
/* unused vector to store application start address */
#define APPVECT_NUM EE_RDY_vect_num
/* each vector table entry is a 2byte RJMP opcode */
#define RSTVECT_ADDR 0x0000
#define APPVECT_ADDR (APPVECT_NUM * 2)
#define RSTVECT_PAGE_OFFSET (RSTVECT_ADDR % SPM_PAGESIZE)
#define APPVECT_PAGE_OFFSET (APPVECT_ADDR % SPM_PAGESIZE)
/* create RJMP opcode for the vector table */
#define OPCODE_RJMP(addr) (((addr) & 0x0FFF) | 0xC000)
#elif (!defined(ASRE) && !defined (RWWSRE))
#error "Device without bootloader section requires VIRTUAL_BOOT_SECTION"
#endif
/* SLA+R */
#define CMD_WAIT 0x00
#define CMD_READ_VERSION 0x01
#define CMD_ACCESS_MEMORY 0x02
/* internal mappings */
#define CMD_ACCESS_CHIPINFO (0x10 | CMD_ACCESS_MEMORY)
#define CMD_ACCESS_FLASH (0x20 | CMD_ACCESS_MEMORY)
#define CMD_ACCESS_EEPROM (0x30 | CMD_ACCESS_MEMORY)
#define CMD_WRITE_FLASH_PAGE (0x40 | CMD_ACCESS_MEMORY)
#define CMD_WRITE_EEPROM_PAGE (0x50 | CMD_ACCESS_MEMORY)
/* SLA+W */
#define CMD_SWITCH_APPLICATION CMD_READ_VERSION
/* internal mappings */
#define CMD_BOOT_BOOTLOADER (0x10 | CMD_SWITCH_APPLICATION) /* only in APP */
#define CMD_BOOT_APPLICATION (0x20 | CMD_SWITCH_APPLICATION)
/* CMD_SWITCH_APPLICATION parameter */
#define BOOTTYPE_BOOTLOADER 0x00 /* only in APP */
#define BOOTTYPE_APPLICATION 0x80
/* CMD_{READ|WRITE}_* parameter */
#define MEMTYPE_CHIPINFO 0x00
#define MEMTYPE_FLASH 0x01
#define MEMTYPE_EEPROM 0x02
/*
* LED_GN flashes with 20Hz (while bootloader is running)
* LED_RT flashes on TWI activity
*
* bootloader twi-protocol:
* - abort boot timeout:
* SLA+W, 0x00, STO
*
* - show bootloader version
* SLA+W, 0x01, SLA+R, {16 bytes}, STO
*
* - start application
* SLA+W, 0x01, 0x80, STO
*
* - read chip info: 3byte signature, 1byte page size, 2byte flash size, 2byte eeprom size
* SLA+W, 0x02, 0x00, 0x00, 0x00, SLA+R, {8 bytes}, STO
*
* - read one (or more) flash bytes
* SLA+W, 0x02, 0x01, addrh, addrl, SLA+R, {* bytes}, STO
*
* - read one (or more) eeprom bytes
* SLA+W, 0x02, 0x02, addrh, addrl, SLA+R, {* bytes}, STO
*
* - write one flash page
* SLA+W, 0x02, 0x01, addrh, addrl, {* bytes}, STO
*
* - write one (or more) eeprom bytes
* SLA+W, 0x02, 0x02, addrh, addrl, {* bytes}, STO
*/
const static uint8_t info[16] = VERSION_STRING;
const static uint8_t chipinfo[8] = {
SIGNATURE_0, SIGNATURE_1, SIGNATURE_2,
SPM_PAGESIZE,
(BOOTLOADER_START >> 8) & 0xFF,
BOOTLOADER_START & 0xFF,
#if (EEPROM_SUPPORT)
((E2END +1) >> 8 & 0xFF),
(E2END +1) & 0xFF
#else
0x00, 0x00
#endif
};
static uint8_t boot_timeout = TIMER_MSEC2IRQCNT(TIMEOUT_MS);
static uint8_t cmd = CMD_WAIT;
/* flash buffer */
static uint8_t buf[SPM_PAGESIZE];
static uint16_t addr;
#if (VIRTUAL_BOOT_SECTION)
/* reset/application vectors received from host, needed for verify read */
static uint8_t rstvect_save[2];
static uint8_t appvect_save[2];
#endif /* (VIRTUAL_BOOT_SECTION) */
/* *************************************************************************
* write_flash_page
* ************************************************************************* */
static void write_flash_page(void)
{
uint16_t pagestart = addr;
uint8_t size = SPM_PAGESIZE;
uint8_t *p = buf;
#if (VIRTUAL_BOOT_SECTION)
if (pagestart == (RSTVECT_ADDR & ~(SPM_PAGESIZE -1)))
{
/* save original vectors for verify read */
rstvect_save[0] = buf[RSTVECT_PAGE_OFFSET];
rstvect_save[1] = buf[RSTVECT_PAGE_OFFSET + 1];
appvect_save[0] = buf[APPVECT_PAGE_OFFSET];
appvect_save[1] = buf[APPVECT_PAGE_OFFSET + 1];
/* replace reset vector with jump to bootloader address */
uint16_t rst_vector = OPCODE_RJMP(BOOTLOADER_START -1);
buf[RSTVECT_PAGE_OFFSET] = (rst_vector & 0xFF);
buf[RSTVECT_PAGE_OFFSET + 1] = (rst_vector >> 8) & 0xFF;
/* replace application vector with jump to original reset vector */
uint16_t app_vector = rstvect_save[0] | (rstvect_save[1] << 8);
app_vector = OPCODE_RJMP(app_vector - APPVECT_NUM);
buf[APPVECT_PAGE_OFFSET] = (app_vector & 0xFF);
buf[APPVECT_PAGE_OFFSET + 1] = (app_vector >> 8) & 0xFF;
}
#endif /* (VIRTUAL_BOOT_SECTION) */
if (pagestart < BOOTLOADER_START)
{
boot_page_erase(pagestart);
boot_spm_busy_wait();
do {
uint16_t data = *p++;
data |= *p++ << 8;
boot_page_fill(addr, data);
addr += 2;
size -= 2;
} while (size);
boot_page_write(pagestart);
boot_spm_busy_wait();
#if defined (ASRE) || defined (RWWSRE)
/* only required for bootloader section */
boot_rww_enable();
#endif
}
} /* write_flash_page */
#if (EEPROM_SUPPORT)
/* *************************************************************************
* read_eeprom_byte
* ************************************************************************* */
static uint8_t read_eeprom_byte(uint16_t address)
{
EEARL = address;
EEARH = (address >> 8);
EECR |= (1<<EERE);
return EEDR;
} /* read_eeprom_byte */
/* *************************************************************************
* write_eeprom_byte
* ************************************************************************* */
static void write_eeprom_byte(uint8_t val)
{
EEARL = addr;
EEARH = (addr >> 8);
EEDR = val;
addr++;
#if defined (EEWE)
EECR |= (1<<EEMWE);
EECR |= (1<<EEWE);
#elif defined (EEPE)
EECR |= (1<<EEMPE);
EECR |= (1<<EEPE);
#else
#error "EEWE/EEPE not defined"
#endif
eeprom_busy_wait();
} /* write_eeprom_byte */
#if (USE_CLOCKSTRETCH == 0)
/* *************************************************************************
* write_eeprom_buffer
* ************************************************************************* */
static void write_eeprom_buffer(uint8_t size)
{
uint8_t *p = buf;
while (size--)
{
write_eeprom_byte(*p++);
}
} /* write_eeprom_buffer */
#endif /* (USE_CLOCKSTRETCH == 0) */
#endif /* EEPROM_SUPPORT */
/* *************************************************************************
* TWI_data_write
* ************************************************************************* */
static uint8_t TWI_data_write(uint8_t bcnt, uint8_t data)
{
uint8_t ack = 0x01;
switch (bcnt)
{
case 0:
switch (data)
{
case CMD_SWITCH_APPLICATION:
case CMD_ACCESS_MEMORY:
/* no break */
case CMD_WAIT:
/* abort countdown */
boot_timeout = 0;
cmd = data;
break;
default:
/* boot app now */
cmd = CMD_BOOT_APPLICATION;
ack = 0x00;
break;
}
break;
case 1:
switch (cmd)
{
case CMD_SWITCH_APPLICATION:
if (data == BOOTTYPE_APPLICATION)
{
cmd = CMD_BOOT_APPLICATION;
}
ack = 0x00;
break;
case CMD_ACCESS_MEMORY:
if (data == MEMTYPE_CHIPINFO)
{
cmd = CMD_ACCESS_CHIPINFO;
}
else if (data == MEMTYPE_FLASH)
{
cmd = CMD_ACCESS_FLASH;
}
#if (EEPROM_SUPPORT)
else if (data == MEMTYPE_EEPROM)
{
cmd = CMD_ACCESS_EEPROM;
}
#endif /* (EEPROM_SUPPORT) */
else
{
ack = 0x00;
}
break;
default:
ack = 0x00;
break;
}
break;
case 2:
case 3:
addr <<= 8;
addr |= data;
break;
default:
switch (cmd)
{
#if (EEPROM_SUPPORT)
#if (USE_CLOCKSTRETCH)
case CMD_ACCESS_EEPROM:
write_eeprom_byte(data);
break;
#else
case CMD_ACCESS_EEPROM:
cmd = CMD_WRITE_EEPROM_PAGE;
/* fall through */
case CMD_WRITE_EEPROM_PAGE:
#endif /* (USE_CLOCKSTRETCH) */
#endif /* (EEPROM_SUPPORT) */
case CMD_ACCESS_FLASH:
{
uint8_t pos = bcnt -4;
buf[pos] = data;
if (pos >= (sizeof(buf) -2))
{
ack = 0x00;
}
if ((cmd == CMD_ACCESS_FLASH) &&
(pos >= (sizeof(buf) -1))
)
{
#if (USE_CLOCKSTRETCH)
write_flash_page();
#else
cmd = CMD_WRITE_FLASH_PAGE;
#endif
}
break;
}
default:
ack = 0x00;
break;
}
break;
}
return ack;
} /* TWI_data_write */
/* *************************************************************************
* TWI_data_read
* ************************************************************************* */
static uint8_t TWI_data_read(uint8_t bcnt)
{
uint8_t data;
switch (cmd)
{
case CMD_READ_VERSION:
bcnt %= sizeof(info);
data = info[bcnt];
break;
case CMD_ACCESS_CHIPINFO:
bcnt %= sizeof(chipinfo);
data = chipinfo[bcnt];
break;
case CMD_ACCESS_FLASH:
switch (addr)
{
/* return cached values for verify read */
#if (VIRTUAL_BOOT_SECTION)
case RSTVECT_ADDR:
data = rstvect_save[0];
break;
case (RSTVECT_ADDR + 1):
data = rstvect_save[1];
break;
case APPVECT_ADDR:
data = appvect_save[0];
break;
case (APPVECT_ADDR + 1):
data = appvect_save[1];
break;
#endif /* (VIRTUAL_BOOT_SECTION) */
default:
data = pgm_read_byte_near(addr);
break;
}
addr++;
break;
#if (EEPROM_SUPPORT)
case CMD_ACCESS_EEPROM:
data = read_eeprom_byte(addr++);
break;
#endif /* (EEPROM_SUPPORT) */
default:
data = 0xFF;
break;
}
return data;
} /* TWI_data_read */
#if defined (TWCR)
/* *************************************************************************
* TWI_vect
* ************************************************************************* */
static void TWI_vect(void)
{
static uint8_t bcnt;
uint8_t control = TWCR;
switch (TWSR & 0xF8)
{
/* SLA+W received, ACK returned -> receive data and ACK */
case 0x60:
bcnt = 0;
LED_RT_ON();
break;
/* prev. SLA+W, data received, ACK returned -> receive data and ACK */
case 0x80:
if (TWI_data_write(bcnt++, TWDR) == 0x00)
{
/* the ACK returned by TWI_data_write() is not for the current
* data in TWDR, but for the next byte received
*/
control &= ~(1<<TWEA);
}
break;
/* SLA+R received, ACK returned -> send data */
case 0xA8:
bcnt = 0;
LED_RT_ON();
/* fall through */
/* prev. SLA+R, data sent, ACK returned -> send data */
case 0xB8:
TWDR = TWI_data_read(bcnt++);
break;
/* prev. SLA+W, data received, NACK returned -> IDLE */
case 0x88:
TWI_data_write(bcnt++, TWDR);
/* fall through */
/* STOP or repeated START -> IDLE */
case 0xA0:
#if (USE_CLOCKSTRETCH == 0)
if ((cmd == CMD_WRITE_FLASH_PAGE)
#if (EEPROM_SUPPORT)
|| (cmd == CMD_WRITE_EEPROM_PAGE)
#endif
)
{
/* disable ACK for now, re-enable after page write */
control &= ~(1<<TWEA);
TWCR = (1<<TWINT) | control;
#if (EEPROM_SUPPORT)
if (cmd == CMD_WRITE_EEPROM_PAGE)
{
write_eeprom_buffer(bcnt -4);
}
else
#endif /* (EEPROM_SUPPORT) */
{
write_flash_page();
}
}
#endif /* (USE_CLOCKSTRETCH) */
bcnt = 0;
/* fall through */
/* prev. SLA+R, data sent, NACK returned -> IDLE */
case 0xC0:
LED_RT_OFF();
control |= (1<<TWEA);
break;
/* illegal state(s) -> reset hardware */
default:
control |= (1<<TWSTO);
break;
}
TWCR = (1<<TWINT) | control;
} /* TWI_vect */
#endif /* defined (TWCR) */
#if defined (USICR)
/* *************************************************************************
* usi_statemachine
* ************************************************************************* */
static void usi_statemachine(uint8_t usisr)
{
static uint8_t usi_state;
static uint8_t bcnt;
uint8_t data = USIDR;
uint8_t state = usi_state & USI_STATE_MASK;
/* Start Condition detected */
if (usisr & (1<<USISIF))
{
/* wait until SCL goes low */
while (USI_PIN_SCL());
usi_state = USI_STATE_SLA | USI_ENABLE_SCL_HOLD;
state = USI_STATE_IDLE;
}
/* Stop Condition detected */
if (usisr & (1<<USIPF))
{
LED_RT_OFF();
usi_state = USI_STATE_IDLE;
state = USI_STATE_IDLE;
}
if (state == USI_STATE_IDLE)
{
/* do nothing */
}
/* Slave Address received => prepare ACK/NAK */
else if (state == USI_STATE_SLA)
{
bcnt = 0;
/* SLA+W received -> send ACK */
if (data == ((TWI_ADDRESS<<1) | 0x00))
{
LED_RT_ON();
usi_state = USI_STATE_SLAW_ACK | USI_WAIT_FOR_ACK | USI_ENABLE_SDA_OUTPUT | USI_ENABLE_SCL_HOLD;
USIDR = 0x00;
}
/* SLA+R received -> send ACK */
else if (data == ((TWI_ADDRESS<<1) | 0x01))
{
LED_RT_ON();
usi_state = USI_STATE_SLAR_ACK | USI_WAIT_FOR_ACK | USI_ENABLE_SDA_OUTPUT | USI_ENABLE_SCL_HOLD;
USIDR = 0x00;
}
/* not addressed -> send NAK */
else
{
usi_state = USI_STATE_NAK | USI_WAIT_FOR_ACK | USI_ENABLE_SDA_OUTPUT | USI_ENABLE_SCL_HOLD;
USIDR = 0x80;
}
}
/* sent NAK -> go to idle */
else if (state == USI_STATE_NAK)
{
usi_state = USI_STATE_IDLE;
}
/* sent ACK after SLA+W -> wait for data */
/* sent ACK after DAT+W -> wait for more data */
else if ((state == USI_STATE_SLAW_ACK) ||
(state == USI_STATE_DATW_ACK)
)
{
usi_state = USI_STATE_DATW | USI_ENABLE_SCL_HOLD;
}
/* data received -> send ACK/NAK */
else if (state == USI_STATE_DATW)
{
if (TWI_data_write(bcnt++, data))
{
usi_state = USI_STATE_DATW_ACK | USI_WAIT_FOR_ACK | USI_ENABLE_SDA_OUTPUT | USI_ENABLE_SCL_HOLD;
USIDR = 0x00;
}
else
{
usi_state = USI_STATE_NAK | USI_WAIT_FOR_ACK | USI_ENABLE_SDA_OUTPUT | USI_ENABLE_SCL_HOLD;
USIDR = 0x80;
}
}
/* sent ACK after SLA+R -> send data */
/* received ACK after DAT+R -> send more data */
else if ((state == USI_STATE_SLAR_ACK) ||
((state == USI_STATE_DATR_ACK) && !(data & 0x01))
)
{
USIDR = TWI_data_read(bcnt++);
usi_state = USI_STATE_DATR | USI_ENABLE_SDA_OUTPUT | USI_ENABLE_SCL_HOLD;
}
/* sent data after SLA+R -> receive ACK/NAK */
else if (state == USI_STATE_DATR)
{
usi_state = USI_STATE_DATR_ACK | USI_WAIT_FOR_ACK | USI_ENABLE_SCL_HOLD;
USIDR = 0x80;
}
/* received NAK after DAT+R -> go to idle */
else if ((state == USI_STATE_DATR_ACK) && (data & 0x01))
{
usi_state = USI_STATE_IDLE;
}
/* default -> go to idle */
else
{
usi_state = USI_STATE_IDLE;
}
/* set SDA direction according to current state */
if (usi_state & USI_ENABLE_SDA_OUTPUT)
{
USI_PIN_SDA_OUTPUT();
}
else
{
USI_PIN_SDA_INPUT();
}
if (usi_state & USI_ENABLE_SCL_HOLD)
{
/* Enable TWI Mode, hold SCL low after counter overflow, count both SCL edges */
USICR = (1<<USIWM1) | (1<<USIWM0) | (1<<USICS1);
}
else
{
/* Enable TWI, hold SCL low only after start condition, count both SCL edges */
USICR = (1<<USIWM1) | (1<<USICS1);
}
/* clear start/overflow/stop condition flags */
usisr &= ((1<<USISIF) | (1<<USIOIF) | (1<<USIPF));
if (usi_state & USI_WAIT_FOR_ACK)
{
/* count 2 SCL edges (ACK/NAK bit) */
USISR = usisr | ((16 -2)<<USICNT0);
}
else
{
/* count 16 SCL edges (8bit data) */
USISR = usisr | ((16 -16)<<USICNT0);
}
} /* usi_statemachine */
#endif /* defined (USICR) */
/* *************************************************************************
* TIMER0_OVF_vect
* ************************************************************************* */
static void TIMER0_OVF_vect(void)
{
/* restart timer */
TCNT0 = 0xFF - TIMER_MSEC2TICKS(TIMER_IRQFREQ_MS);
/* blink LED while running */
LED_GN_TOGGLE();
/* count down for app-boot */
if (boot_timeout > 1)
{
boot_timeout--;
}
else if (boot_timeout == 1)
{
/* trigger app-boot */
cmd = CMD_BOOT_APPLICATION;
}
} /* TIMER0_OVF_vect */
#if (VIRTUAL_BOOT_SECTION)
static void (*jump_to_app)(void) __attribute__ ((noreturn)) = (void*)APPVECT_ADDR;
#else
static void (*jump_to_app)(void) __attribute__ ((noreturn)) = (void*)0x0000;
#endif
/* *************************************************************************
* init1
* ************************************************************************* */
void init1(void) __attribute__((naked, section(".init1")));
void init1(void)
{
/* make sure r1 is 0x00 */
asm volatile ("clr __zero_reg__");
/* on some MCUs the stack pointer defaults NOT to RAMEND */
#if defined(__AVR_ATmega8__) || defined(__AVR_ATmega8515__) || \
defined(__AVR_ATmega8535__) || defined (__AVR_ATmega16__) || \
defined (__AVR_ATmega32__) || defined (__AVR_ATmega64__) || \
defined (__AVR_ATmega128__) || defined (__AVR_ATmega162__)
SP = RAMEND;
#endif
} /* init1 */
/*
* For newer devices the watchdog timer remains active even after a
* system reset. So disable it as soon as possible.
* automagically called on startup
*/
#if defined (__AVR_ATmega88__) || defined (__AVR_ATmega168__) || \
defined (__AVR_ATmega328P__)
/* *************************************************************************
* disable_wdt_timer
* ************************************************************************* */
void disable_wdt_timer(void) __attribute__((naked, section(".init3")));
void disable_wdt_timer(void)
{
MCUSR = 0;
WDTCSR = (1<<WDCE) | (1<<WDE);
WDTCSR = (0<<WDE);
} /* disable_wdt_timer */
#endif
/* *************************************************************************
* main
* ************************************************************************* */
int main(void) __attribute__ ((OS_main, section (".init9")));
int main(void)
{
LED_INIT();
LED_GN_ON();
#if (VIRTUAL_BOOT_SECTION)
/* load current values (for reading flash) */
rstvect_save[0] = pgm_read_byte_near(RSTVECT_ADDR);
rstvect_save[1] = pgm_read_byte_near(RSTVECT_ADDR + 1);
appvect_save[0] = pgm_read_byte_near(APPVECT_ADDR);
appvect_save[1] = pgm_read_byte_near(APPVECT_ADDR + 1);
#endif /* (VIRTUAL_BOOT_SECTION) */
/* timer0: running with F_CPU/1024 */
#if defined (TCCR0)
TCCR0 = (1<<CS02) | (1<<CS00);
#elif defined (TCCR0B)
TCCR0B = (1<<CS02) | (1<<CS00);
#else
#error "TCCR0(B) not defined"
#endif
#if defined (TWCR)
/* TWI init: set address, auto ACKs */
TWAR = (TWI_ADDRESS<<1);
TWCR = (1<<TWEA) | (1<<TWEN);
#elif defined (USICR)
USI_PIN_INIT();
usi_statemachine(0x00);
#else
#error "No TWI/USI peripheral found"
#endif
while (cmd != CMD_BOOT_APPLICATION)
{
#if defined (TWCR)
if (TWCR & (1<<TWINT))
{
TWI_vect();
}
#elif defined (USICR)
if (USISR & ((1<<USISIF) | (1<<USIOIF) | (1<<USIPF)))
{
usi_statemachine(USISR);
}
#endif
#if defined (TIFR)
if (TIFR & (1<<TOV0))
{
TIMER0_OVF_vect();
TIFR = (1<<TOV0);
}
#elif defined (TIFR0)
if (TIFR0 & (1<<TOV0))
{
TIMER0_OVF_vect();
TIFR0 = (1<<TOV0);
}
#else
#error "TIFR(0) not defined"
#endif
}
#if defined (TWCR)
/* Disable TWI but keep address! */
TWCR = 0x00;
#elif defined (USICR)
/* Disable USI peripheral */
USICR = 0x00;
#endif
/* disable timer0 */
#if defined (TCCR0)
TCCR0 = 0x00;
#elif defined (TCCR0B)
TCCR0B = 0x00;
#else
#error "TCCR0(B) not defined"
#endif
LED_OFF();
#if (LED_SUPPORT)
uint16_t wait = 0x0000;
do {
__asm volatile ("nop");
} while (--wait);
#endif /* (LED_SUPPORT) */
jump_to_app();
} /* main */