// watch external clock for PWM messages
// specify minimum gap to look for in us
void sniff_pwm(unsigned int min)
{
BOOL toggle;
BOOL abort= FALSE;
unsigned long i, count, pulsecount= 0L, gaps[DETECT_BUFFER_SIZE], pulses[DETECT_BUFFER_SIZE];
// make sure local clock isn't running & switch to input
stop_HW_clock();
COIL_MODE_READER();
READER_CLOCK_ENABLE_OFF(LOW);
toggle= SNIFFER_COIL;
// wait for 100 ticks to make sure we're settled
toggle= SNIFFER_COIL;
while(count < 100)
{
while(SNIFFER_COIL == toggle)
// check for user abort
if(get_user_abort())
return;
++count;
toggle= !toggle;
}
// watch for gaps / pulses
i= 0;
GetTimer_us(RESET);
while(!abort)
{
while(SNIFFER_COIL == toggle)
// check for user abort
if((abort= get_user_abort()))
break;
toggle= !toggle;
count= GetTimer_us(RESET);
// check if it was a gap
if(count > min)
{
pulses[i]= pulsecount;
gaps[i++]= count;
pulsecount= 0L;
}
else
pulsecount += count;
if(i == DETECT_BUFFER_SIZE)
{
decode_pwm(pulses, gaps, i);
i= 0;
}
}
decode_pwm(pulses, gaps, i);
}
// Reader clock ISR
// also process RWD commands while we toggle clock line
void __ISR(_OUTPUT_COMPARE_5_VECTOR, ipl6auto) reader_clock_tick (void)
{
static unsigned int count= 0;
static unsigned int bcount= 0;
// Clear interrupt flag
mOC5ClearIntFlag();
mLED_Clock_On();
// process RWD commands (if any)
switch (RWD_State)
{
case RWD_STATE_INACTIVE:
case RWD_STATE_ACTIVE:
//DEBUG_PIN_4= !DEBUG_PIN_4;
break;
case RWD_STATE_GO_TO_SLEEP:
//DEBUG_PIN_4= !DEBUG_PIN_4;
//DEBUG_PIN_4= !DEBUG_PIN_4;
// initial shutdown of coil to restart tag
READER_CLOCK_ENABLE_OFF();
COIL_OUT_LOW();
// time small amounts with ticks, large with uS
if(RWD_Sleep_Period > MAX_TIMER5_TICKS)
Delay_us(CONVERT_TICKS_TO_US(RWD_Sleep_Period));
else
{
WriteTimer5(0);
while(GetTimer_ticks(NO_RESET) < RWD_Sleep_Period)
;
}
count= 0;
RWD_State= RWD_STATE_WAKING;
// restart clock only if we have a wake period
if(RWD_Wake_Period)
READER_CLOCK_ENABLE_ON();
break;
case RWD_STATE_WAKING:
//DEBUG_PIN_4= !DEBUG_PIN_4;
// leave coil running for wakeup period
if(count == RWD_Wake_Period)
{
count= 0;
bcount = 0;
if(*RWD_Command_ThisBit != '*')
RWD_State= RWD_STATE_START_SEND;
else
RWD_State= RWD_STATE_ACTIVE;
}
else
count++;
break;
case RWD_STATE_START_SEND:
//DEBUG_PIN_4= !DEBUG_PIN_4;
// send initial gap
// stop modulation of coil and wait
READER_CLOCK_ENABLE_OFF();
COIL_OUT_LOW();
count= 0;
if(RWD_Barrier)
RWD_State= RWD_STATE_SENDING_BARRIER_LOW;
else
RWD_State= RWD_STATE_SENDING_BIT_LOW;
//DEBUG_PIN_4= !DEBUG_PIN_4;
// restart clock
//READER_CLOCK_ENABLE_ON();
break;
case RWD_STATE_SENDING_BIT_HIGH:
//DEBUG_PIN_4= !DEBUG_PIN_4;
// clock running for bit period, then wait for gap period
if((*RWD_Command_ThisBit && count == RWD_One_Period) || (!*RWD_Command_ThisBit && count == RWD_Zero_Period))
{
count= 0;
if(*RWD_Command_ThisBit == '*')
RWD_State= RWD_STATE_POST_WAIT;
else if(RWD_Barrier && bcount == 7)
RWD_State= RWD_STATE_SENDING_BARRIER_LOW;
else
RWD_State= RWD_STATE_SENDING_BIT_LOW;
READER_CLOCK_ENABLE_OFF();
COIL_OUT_LOW();
bcount++;
if(bcount == 8)
bcount = 0;
}
else
count++;
break;
case RWD_STATE_SENDING_BIT_LOW:
if((*RWD_Command_ThisBit && count == RWD_One_Gap_Period) || (!*RWD_Command_ThisBit && count == RWD_Zero_Gap_Period))
{
++RWD_Command_ThisBit;
count= 0;
RWD_State= RWD_STATE_SENDING_BIT_HIGH;
// restart clock
READER_CLOCK_ENABLE_ON();
}
else
count++;
break;
case RWD_STATE_SENDING_BARRIER_HIGH:
if(count == RWD_One_Barrier_Period){
count= 0;
RWD_State= RWD_STATE_SENDING_BIT_LOW;
READER_CLOCK_ENABLE_OFF();
COIL_OUT_LOW();
}else
count++;
break;
case RWD_STATE_SENDING_BARRIER_LOW:
if(count == RWD_Zero_Barrier_Period){
count= 0;
RWD_State= RWD_STATE_SENDING_BARRIER_HIGH;
READER_CLOCK_ENABLE_ON();
}else
count++;
break;
case RWD_STATE_POST_WAIT:
//DEBUG_PIN_4= !DEBUG_PIN_4;
// coil running for forced post-command wait period
if(count == RWD_Post_Wait)
{
count= 0;
RWD_State= RWD_STATE_ACTIVE;
}
else
count++;
break;
default:
break;
}
}
