Rescue clock of the AVRISP-MKII moved to the AVR's OCR1A pin, so that the clock can...

[pub/lufa.git] / Projects / AVRISP-MKII / Lib / ISP / ISPTarget.c

diff --git a/Projects/AVRISP-MKII/Lib/ISP/ISPTarget.c b/Projects/AVRISP-MKII/Lib/ISP/ISPTarget.c
index e596cfe..fe2f50d 100644 (file)
--- a/Projects/AVRISP-MKII/Lib/ISP/ISPTarget.c
+++ b/Projects/AVRISP-MKII/Lib/ISP/ISPTarget.c
@@ -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