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SpenceKonde committed Sep 17, 2022
2 parents 305a28f + 4cc48a0 commit dfe5bf4
Showing 1 changed file with 30 additions and 62 deletions.
92 changes: 30 additions & 62 deletions megaavr/cores/megatinycore/wiring.c
Original file line number Diff line number Diff line change
Expand Up @@ -153,59 +153,18 @@ inline unsigned long microsecondsToClockCycles(unsigned long microseconds) {
#elif defined(MILLIS_USE_TIMERRTC)
ISR(RTC_CNT_vect)
#else //otherwise it's a TCB *or* no MILLIS_USE_TIMER macros are defined, including MILLIS_USE_TIMER_NONE
#if defined(MEGATINYCORE) // tinyAVRs use the dart board approach to locating the peripherals :-(
#if defined(MILLIS_USE_TIMERB0)
#if (MEGATINYCORE_SERIES != 2)
#define _CLEARFLAG "sts 0x0A46, r24"
#else
#define _CLEARFLAG "sts 0x0A86, r24"
#endif
ISR(TCB0_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB1)
#if (MEGATINYCORE_SERIES != 2)
#define _CLEARFLAG "sts 0x0A56, r24"
#else
#define _CLEARFLAG "sts 0x0A96, r24"
#endif
ISR(TCB1_INT_vect, ISR_NAKED)
#else
#error "No millis timer selected, but not disabled - cannot determine millis vector"
#endif
#elif defined(DXCORE) //Dx and Ex series start their TCB's at 0xB00
#if defined(MILLIS_USE_TIMERB0)
#define _CLEARFLAG "sts 0x0B06, r24"
ISR(TCB0_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB1)
#define _CLEARFLAG "sts 0x0B16, r24"
ISR(TCB1_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB2)
#define _CLEARFLAG "sts 0x0B26, r24"
ISR(TCB2_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB3)
#define _CLEARFLAG "sts 0x0B36, r24"
ISR(TCB3_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB4)
#define _CLEARFLAG "sts 0x0B46, r24"
ISR(TCB4_INT_vect, ISR_NAKED)
#else
#error "No millis timer selected, but not disabled - cannot determine millis vector"
#endif
#else //Otherwise it would have to be.... a mega0-series (which this file isn't designed to support) but in the interest of making this code usable on all modern AVRs:
#if defined(MILLIS_USE_TIMERB0)
#define _CLEARFLAG "sts 0x0A86, r24"
ISR(TCB0_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB1)
#define _CLEARFLAG "sts 0x0A96, r24"
ISR(TCB1_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB2)
#define _CLEARFLAG "sts 0x0AA6, r24"
ISR(TCB2_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB3)
#define _CLEARFLAG "sts 0x0AB6, r24"
ISR(TCB3_INT_vect, ISR_NAKED)
#else
#error "No millis timer selected, but not disabled - cannot determine millis vector"
#endif
#if defined(MILLIS_USE_TIMERB0)
ISR(TCB0_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB1)
ISR(TCB1_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB2)
ISR(TCB2_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB3)
ISR(TCB3_INT_vect, ISR_NAKED)
#elif defined(MILLIS_USE_TIMERB4)
ISR(TCB4_INT_vect, ISR_NAKED)
#else
#error "No millis timer selected, but not disabled - cannot determine millis vector"
#endif
#endif // end of ISR statement, now for the ISR body
{
Expand All @@ -223,7 +182,11 @@ inline unsigned long microsecondsToClockCycles(unsigned long microseconds) {
"in r24, 0x3F" "\n\t" // Need to save SREG too
"push r24" "\n\t" // and push the SREG value - 7 clocks here + the 5-6 to enter the ISR depending on flash and sketch size, 12-13 total
"ld r24, X" "\n\t" // X points to LSB of timer_millis, load the LSB
"subi r24, %[DEC]" "\n\t" // "decrement" (actually increment) it by the desired value
#if (F_CPU > 2000000) // if it's 1 or 2 MHz, millis timer overflows every 2ms, intentionally sacrificing resolution for reduced time spent in ISR
"subi r24, 0xFF" "\n\t" // sub 0xFF is the same as to add 1
#else
"subi r24, 0xFE" "\n\t" // sub 0xFE is the same as to add 2
#endif
"st X+, r24" "\n\t" // Store incremented value back to X, post-increment X
"ld r24, X" "\n\t" // now second byte pointed to by X, load that
"sbci r24, 0xFF" "\n\t" // because this is sbci, it treats carry bit like subtraction, and unless we did just roll over the last byte
Expand All @@ -235,21 +198,26 @@ inline unsigned long microsecondsToClockCycles(unsigned long microseconds) {
"sbci r24, 0xFF" "\n\t" //
"st X, r24" "\n\t" // ... until all 4 bytes were handled, at 4 clocks and 3 words per byte -> 16 clocks
"ldi r24, 0x01" "\n\t" // This is the TCB intflag, which we will store with sts using the line #defined above. 1 clock
_CLEARFLAG "\n\t" // defined above. Yes, the preprocessor lets you do dumb shit like this! 2 clocks for sts
"sts %[PTCLR], r24" "\n\t" // defined above. Yes, the preprocessor lets you do dumb shit like this! 2 clocks for sts
"pop r24" "\n\t" // pop r24 to get the old SREG value - 2 clock
"out 0x3F, r24" "\n\t" // restore SREG - 1 clock
"pop r24" "\n\t"
"pop r27" "\n\t"
"pop r26" "\n\t" // 6 more clocks popping registers in reverse order.
"reti" "\n\t" // and 4 clocks for reti - total 12/13 + 16 + 2 + 1 + 6 + 4 = 41/42 clocks total, and 7+16+3+6 = 32 words, vs 60-61 clocks and 40 words
:: "x" (&timer_millis), // we are changing the value of this, so to be strictly correct, this must be declared input output - though in this case it doesn't matter
#if (F_CPU > 2000000)
[DEC] "M" (0xFF) // sub 0xFF is the same as to add 1
#else // if it's 1 or 2 MHz, we set the millis timer to only overflow every 2 milliseconds, intentionally sacrificing resolution for reduced time spent in ISR
[DEC] "M" (0xFE) // sub 0xFE is the same as to add 2
#endif
// No clobber because the register is saved and restored, and this is a naked isr, so it doesn't get prologue or epilogue generated.
:: "x" (&timer_millis), // we are changing the value of this, so to be strictly correct, this must be declared input output - though in this case it doesn't matter
[PTCLR] "m" (_timer->INTFLAGS)
); // grrr, sublime highlights this as invalid syntax because it gets confused by the ifdef's and odd syntax on inline asm
/* ISR in C:
ISR (TCBx_INT_vect) { // x depends on user configuration
#if (F_CPU > 2000000)
timer_millis += 1;
#else
timer_millis += 2;
#endif
_timer->INTFLAGS = TCB_CAPT_bm; // reset Interrupt flag of TCBx
}
*/
#else
#if defined(MILLIS_USE_TIMERRTC)
// if RTC is used as timer, we only increment the overflow count
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