QDK PIC24/dsPIC-C30 - Quantum Leaps

QDK
PIC24/dsPIC-C30
www.state-machine.com/pic
The following Listing 10 shows an example implementation of QK_onIdle() for the PIC24/dsPIC. Please
note that the ilde-LED is turned on and off in a critical section (so that the intensity of the LED does not
include any preemptions by interrupts and tasks). The transition to the Idle mode happens in a very
straightforward way, because transition to idle mode is always safe under a preemptive priority-based
kernel, such as QK.
void QK_onIdle(void) {
Listing 10: QK_onIdle() callback for PIC24/dsPIC.
QF_INT_DISABLE();
LED_ON (IDLE_LED); /* blink the IDLE LED, see NOTE01 */
LED_OFF(IDLE_LED);
QF_INT_ENABLE();
#ifdef Q_SPY
while (U2STAbits.UTXBF == 0U) { /* TX Buffer not full */
uint16_t b;
QF_INT_DISABLE();
b = QS_getByte();
QF_INT_ENABLE();
if (b == QS_EOD) { /* End-Of-Data reached */
break; /* break out of the loop */
}
U2TXREG = (uint8_t)b; /* stick the byte to TXREG for transmission */
}
#elif defined NDEBUG
Idle(); /* transition to Idle mode */
#endif
}
4.4 Testing QK Preemption Scenarios
The technique described in this section will allow you to use the MPLAB debugger to trigger an interrupt
at any machine instruction and observe the preemptions it causes. The interrupt used for the testing
purposes is the GPIOA interrupt (INTID == 0). The ISR for this interrupt is shown below:
The DPP example application for the preemptive QK kernel includes special ISR (INT0 ISR) for
convenient testing of various preemption scenarios, defined as follows:
#define INT0_ISR_PRIO 6
QK_ISR(auto_psv) _INT0Interrupt() {
static QEvent const eat_evt = { EAT_SIG, 0 };
_INT0IF = 0;
QACTIVE_POST(AO_Table, &eat_evt, &l_INT0Interrupt);
QK_ISR_EXIT(); /* inform QK about exiting the ISR */
}
The INT0 ISR, is assigned priority 6, which is higher than the priority of the system clock tick ISR.
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