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Rescue clock of the AVRISP-MKII moved to the AVR's OCR1A pin, so that the clock can be generated at all times when 125KHz ISP programming mode is selected.

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This commit is contained in:
Dean Camera 2010-11-02 07:57:23 +00:00
parent 40db485c79
commit 3bf760ad7d
7 changed files with 56 additions and 25 deletions
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49
Projects/AVRISP-MKII/Lib/ISP/ISPTarget.c
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@ -119,7 +119,7 @@ ISR(TIMER1_COMPA_vect, ISR_BLOCK)
{
if (!(PINB & (1 << 1)))
{
if (SoftSPI_Data & 0x80)
if (SoftSPI_Data & (1 << 7))
PORTB |= (1 << 2);
else
PORTB &= ~(1 << 2);
@ -132,10 +132,11 @@ ISR(TIMER1_COMPA_vect, ISR_BLOCK)
TCCR1B = 0;
if (PINB & (1 << 3))
SoftSPI_Data |= 0x01;
SoftSPI_Data |= (1 << 0);
}
PORTB ^= (1 << 1);
/* Fast toggle of PORTB.1 via the PIN register (see datasheet) */
PINB |= (1 << 1);
}
/** Initialises the appropriate SPI driver (hardware or software, depending on the selected ISP speed) ready for
@ -159,8 +160,7 @@ void ISPTarget_Init(void)
DDRB |= ((1 << 1) | (1 << 2));
PORTB |= ((1 << 0) | (1 << 3));
TIMSK1 = (1 << OCIE1A);
OCR1A = pgm_read_word(&TimerCompareFromSCKDuration[SCKDuration - sizeof(SPIMaskFromSCKDuration)]);
ISPTarget_ConfigureSoftwareISP(SCKDuration);
}
}
@ -177,9 +177,48 @@ void ISPTarget_ShutDown(void)
{
DDRB &= ~((1 << 1) | (1 << 2));
PORTB &= ~((1 << 0) | (1 << 3));
ISPTarget_ConfigureRescueClock();
}
}
/** Configures the AVR to produce a .5MHz rescue clock out of the OCR1A pin of the AVR, so
* that it can be fed into the XTAL1 pin of an AVR whose fuses have been misconfigured for
* an external clock rather than a crystal. When used, the ISP speed must be 125KHz for this
* functionality to work correctly.
*/
void ISPTarget_ConfigureRescueClock(void)
{
/* Configure OCR1A as an output for the specified AVR model */
#if defined(USB_SERIES_2_AVR)
DDRC |= (1 << 6);
#else
DDRB |= (1 << 5);
#endif
/* Start Timer 1 to generate a .5MHz clock on the OCR1A pin */
TIMSK1 = 0;
TCNT1 = 0;
OCR1A = (F_CPU / 2 / 500000UL);
TCCR1A = (1 << COM1A0);
TCCR1B = ((1 << WGM12) | (1 << CS10));
}
/** Configures the AVR's timer ready to produce software ISP for the slower ISP speeds that
* cannot be obtained when using the AVR's hardware SPI module.
*
* \param[in] SCKDuration Duration of the desired software ISP SCK clock
*/
void ISPTarget_ConfigureSoftwareISP(const uint8_t SCKDuration)
{
/* Configure Timer 1 for software ISP using the specified SCK duration */
TIMSK1 = (1 << OCIE1A);
TCNT1 = 0;
OCR1A = pgm_read_word(&TimerCompareFromSCKDuration[SCKDuration - sizeof(SPIMaskFromSCKDuration)]);
TCCR1A = 0;
TCCR1B = 0;
}
/** Sends and receives a single byte of data to and from the attached target via software SPI.
*
* \param[in] Byte Byte of data to send to the attached target