How can I speed this code up? SHIFTOUT is slowing it down and I need a faster way.

[Charles Linquis]

Use a 16 bit counter in assembly to count to 0FFF.
In that loop, use the instruction -

btg LATA.3

You can't get much quicker than that.

I haven't counted exactly, but it looks to be under 14 cycles. At 40Mhz, that is
1.4uSEC = 714 Khz.

[Charles Linquis]

I should have stated that it is 1.4uSec per CYCLE. So 4096 cycles would take 5.8 milliseconds.

[wolwil]

Use a 16 bit counter in assembly to count to 0FFF.
In that loop, use the instruction -

btg LATA.3

You can't get much quicker than that.

I haven't counted exactly, but it looks to be under 14 cycles. At 40Mhz, that is
1.4uSEC = 714 Khz.

so do I just replace this:

	FOR C3 = 0 TO 4095
    		PORTA = %00001000
    		PORTA = %00000000
	NEXT

with this:

FOR C3 = 0 TO 4095
     btg LATA.3
NEXT

I do not know assembly at all thats why I went with PBP and keep in mind I am using a 16MHz Clock but I will be switching it up to a 20MHz

[Charles Linquis]

No, it will take a bit more than that.

I would have posted something more complete, but I don't have access to my development board until Monday. When I get to my board, I'll be able to send you something that has been tested.

[wolwil]

No, it will take a bit more than that.

I would have posted something more complete, but I don't have access to my development board until Monday. When I get to my board, I'll be able to send you something that has been tested.

That would be awesome! Thanks

[Charles Linquis]

That would be awesome! Thanks

It will take me a bit longer than I thought. I think you said you were using a 16F chip. Bad news for me! The 16Fs are missing some of my favorite ASM instructions.

I don't have any 16F stuff lying around, I'll have to find one.

[wolwil]

It will take me a bit longer than I thought. I think you said you were using a 16F chip. Bad news for me! The 16Fs are missing some of my favorite ASM instructions.

I don't have any 16F stuff lying around, I'll have to find one.

Thats alright I have been trying to get it to work with the HPWM but I just dont quite understand how to get it to work. I put a LED on PORTB.0 and typed the following code but nothing happens to the light:

DEFINE OCS 4

C1 VAR WORD

DEFINE CCP1_REG PORTB   'no clue what this does but I think I need it for the following line
DEFINE CCP1_BIT 1     ' because 1 = portb.0 according to the manual I think?

FOR C1 = 0 to 255
HPWM 1,C1,1000 
NEXT

I was thinking I could use this for my clock pulse of 4096 times like this:

FOR C1 = 0 TO 15
HPWM 1,127,frequency '50% duty/square wave
NEXT

for right now I have a second external clock hooked up that I am turning on with throwing a pin high for a couple milliseconds and it fixed what I am trying to fix but its not exact like I need it to be.

Thanks again for your time with this!

[HenrikOlsson]

Hi,
Some PIC's can map the output of the CCP-module to different pins, the 'F88 can map it to either RB0 or RB3. The defines you have tells PBP to generate code to map the CCP1 output to the pin you specify. However, BIT 1 as you've specified means it tries to map it to PORTB.1 which isn't valid.

/Henrik.