AVR Freaks

Taking this one step at a time here.. Timer is not used anymore, it was in the loop to prevent a freeze but my new code does not need it. Its also before the loop anyways.

"This will work if the minimum pulse is long enough." Pulse is always 6-7us.

Once I get this close I'd like to move the loops to ASM. Since the time between pulses are no less then 6us Calling a macro should be ok. Could I get some help on how the macro could look? I'm a bit rusty on ASM, still learning.

So few things here, with my project I do not see my lst file (or was it lss)? Normally AVR studio makes them for me, do I need to do something to make it out put them? I do not know any other way to see my ASM.

Interestinglt this code half works. The rising edge catches it in less then 400 ns but falling is over 500 closer to 600(see image).

        //|___|~~~~|____|
        loadRegister=_low_state_portd_second;
        WHILE_PULSE_IS_LO;
        PORTD = loadRegister;
    
        //|___|~~~~|____|~~~~~|
        loadRegister=_6button;
        WHILE_PULSE_IS_HI;
        PORTD = loadRegister;

but yeah going to need to see the ASM here, how can I do this?

Yeah that got it down.

   //|___|~~~~|
        loadRegister=_low_state_portd_first;
        WHILE_PULSE_IS_HI_NO_CHECK;
    21cc:    36 99           sbic    0x06, 6    ; 6
    21ce:    fe cf           rjmp    .-4          ; 0x21cc <Poll+0x8c>
        PORTD = loadRegister;
    21d0:    3b b9           out    0x0b, r19    ; 11

        //|___|~~~~|____|
        loadRegister=_low_state_portd_second;
        WHILE_PULSE_IS_LO_NO_CHECK;
    21d2:    36 9b           sbis    0x06, 6    ; 6
    21d4:    fe cf           rjmp    .-4          ; 0x21d2 <Poll+0x92>
        PORTD = loadRegister;
    21d6:    8b b9           out    0x0b, r24    ; 11

not working %100 yet but it is about as fast as I'm going to get it, no?

After a lot of observations with the real hardware using a scope, it turns out there is only a concern at the first falling edge.  And it is only for some cases not all). The other edges seem to be 500ns torrential which the ASM can do just fine.

There are two forms, the longer and shorter.

//|___|~~~~|____|~~~~~|____|~~~~|____|

  |

 critical

//|___|

  |

 very critical

The longer form does not seem to be as critical as the shorter one. At least so far... And I know what form is coming and I track that. So, for the short one I set PORTD before the fall because I must react in under 500ns and there are times the ASM below just takes longer then that. So I get a rapid effect where it thinks the response is being pressed off and on. Setting the PORTD and then waiting for the falling edge, does work in this case. As for the longer form, that trick is not working but fortunately timings not as critical. 

if (_console_pulling_mode == 3) PORTD=_low_state_portd_first;

asm volatile(
        "    mov    r31, %0   \n"
        " start%=:     "
        "    sbic   0x06, 6  \n"
        "    rjmp   start%=  \n"    
        "    out   0x0B,  r31\n"
        : : "w" (_low_state_portd_first)
        : "r31"
    );

This works out rather well, but it's a band-aid for the lack of speed. It would be much more efficient if I could get it working without this.  I'll settle for less I guess... Watching the scope I see a range of 300~-500~ ns, guessing 3-5 clock cycles. If there was a way to get just one cycle faster I'd have the perfect solution.  

produced code

2228:    36 99           sbic    0x06, 6    ; 6
222a:    fe cf           rjmp    .-4          ; 0x2228 <start374>
222c:    fb b9           out    0x0b, r31    ; 11

Other though t I had was adding a pull down resister to speed up the lowering of the pulse, thinking its just taking too long to fall. But never played with that idea.  As it is currently there is no resister on the MCU but presumably in the device I'm connected to has a pull up (could measure it).

If I'm at my limit, so be it.

I wrote that pieces in asm ?

Did you mean the surrounding code?

void Poll(void)
{
	unsigned char _low_state_portd_first =0xF3;//prep bits
	unsigned char _low_state_portd_second =0xF3;//prep bits
	unsigned char _low_state_portd_6button_First;//prep bits
	unsigned char _low_state_portd_6button_Second=0xF3;//prep bits
	unsigned char _low_state_portd_6button_Second_Third=0xF3;//prep bits
	
	//set direction
	DDRD |= 0xF3;

	if ( reportBuffer[BUTTON_ROW_1] & 0x20) {_low_state_portd_first &= ~0x01;}//Start
	if ( reportBuffer[BUTTON_ROW_1] & 0x01) {_low_state_portd_first &= ~0x02;}//A

	_low_state_portd_first &= ~0xc0; //controller detection.  
	
	//prep second
	_low_state_portd_second = 0xf3;
	
	if ( reportBuffer[BUTTON_ROW_1] & 0x80) _low_state_portd_second &= ~0x01; //C 
	if ( reportBuffer[BUTTON_ROW_1] & 0x02) _low_state_portd_second &= ~0x02; //B 
	if ( reportBuffer[HAT] == DPAD_RIGHT || reportBuffer[HAT] == DPAD_DOWNRIGHT || reportBuffer[HAT] == DPAD_UPRIGHT) {_low_state_portd_6button_Second_Third |= 0x80; _low_state_portd_first &= ~0x80; _low_state_portd_second  &= ~0x80; }
	if ( reportBuffer[HAT] == DPAD_LEFT || reportBuffer[HAT] == DPAD_DOWNLEFT || reportBuffer[HAT] == DPAD_UPLEFT )	  {_low_state_portd_6button_Second_Third |= 0x40; _low_state_portd_first &= ~0x40; _low_state_portd_second  &= ~0x40; }
	if ( reportBuffer[HAT] == DPAD_UP || reportBuffer[HAT] == DPAD_UPLEFT || reportBuffer[HAT] == DPAD_UPRIGHT)    	  {_low_state_portd_6button_Second_Third |= 0x10; _low_state_portd_first &= ~0x10; _low_state_portd_second  &= ~0x10; }
	if ( reportBuffer[HAT] == DPAD_DOWN || reportBuffer[HAT] == DPAD_DOWNLEFT || reportBuffer[HAT] == DPAD_DOWNRIGHT) {_low_state_portd_6button_Second_Third |= 0x20; _low_state_portd_first &= ~0x20; _low_state_portd_second  &= ~0x20; }

	
	if ( reportBuffer[BUTTON_ROW_1] & 0x40) _low_state_portd_6button_Second  &= ~0x10;//z
	if ( reportBuffer[BUTTON_ROW_1] & 0x08) _low_state_portd_6button_Second  &= ~0x20;//y
	if ( reportBuffer[BUTTON_ROW_1] & 0x04) _low_state_portd_6button_Second  &= ~0x40;//x
	if ( reportBuffer[BUTTON_ROW_1] & 0x10) _low_state_portd_6button_Second  &= ~0x80;//mode

if (_console_pulling_mode == 3) PORTD=_low_state_portd_first;
	asm volatile(
		"	mov    r31, %0   \n"
		" start%=:     "
		"	sbic   0x06, 6  \n"
		"	rjmp   start%=  \n"	
		"	out   0x0B,  r31\n"
		: : "w" (_low_state_portd_first) 
        : "r31"
    );

	if ( _console_pulling_mode==6) 
	{
	_low_state_portd_6button_First=_low_state_portd_first;
	_low_state_portd_6button_First &= ~0xf0;
	
		//|___| 
		asm volatile("start%=:\n sbis 0x06,6 \n rjmp start%=\n":::);//sync to rise.
		PORTD = _low_state_portd_second;
 
		//|___|~~~~|
		asm volatile("start%=:\n sbic 0x06,6 \n rjmp start%=\n":::);//sync to fall.
		PORTD = _low_state_portd_first; 
 
		//|___|~~~~|____|
		asm volatile("start%=:\n sbis 0x06,6 \n rjmp start%=\n":::);//sync to rise.
		PORTD=_low_state_portd_second;

		//|___|~~~~|____|~~~~~|
		asm volatile("start%=:\n sbic 0x06,6 \n rjmp start%=\n":::);//sync to fall.
		PORTD=_low_state_portd_6button_First; 

		//|___|~~~~|____|~~~~~|____|  
		asm volatile("start%=:\n sbis 0x06,6 \n rjmp start%=\n":::);//sync to rise.
		PORTD=_low_state_portd_6button_Second;

		//|___|~~~~|____|~~~~~|____|~~~~~|  
		asm volatile("start%=:\n sbic 0x06,6 \n rjmp start%=\n":::);//sync to fall.
		PORTD = _low_state_portd_6button_Second_Third;
	}
	

	asm volatile("start%=:\n sbis 0x06,6 \n rjmp start%=\n":::);//sync to rise.
	PORTD=_low_state_portd_second;
 

}

Will that change the interaction time for that first falling edge?