Pulsin ir receiver and osc speeds

[jimseng]

Hello with my pic running at 4 mhz this works. At 16 mhz it doesn't. It is due to the pulsin resolution but I can't work out what I need to change in order to get it working. Can someone explain it to my rather meagre brain?

Thanks

DEFINE PULSIN_MAX 1140 '>1140 RETURNS 0


IR VAR byte[4]
pulse VAR word
i VAR byte
stx VAR word 'start of transmission

init: IR[0]=0:IR[1]=0:IR[2]=0:IR[3]=0:i=0
PulsIn PORTA.4, 0, stx
If (stx<760) Then init

While PORTB.4=1:Wend 'wait space
Repeat
PulsIn PORTA.4, 1, pulse
If (pulse>100) Then
IR.0(i)=1 'set bit
EndIf
i=i+1

Until (i>31)
serout portA.5,6,[#IR[0],10,13,#IR[1],10,13,#IR[2],10,13,#IR[3],10,13]

GoTo init

[mackrackit]

This may be a stupid question bur are you changing the OSC define to.
DEFINE OSC 16
when you change resonators or crystals

[jimseng]

Yes. it's actually an internal osc but I understand the pulsin command doesn't care anyway.

[mackrackit]

Correct, PULSIN works with the actual speed the MCU is running at. Are you sure the internal is setup properly... confirmed the MCU is running at the desired speed?

[jimseng]

I am pretty sure it is. (I tested it with a blink led set to pause 2000 and it was a 2 second gap...well two Mississippis by my count. I spent a while trying to figure out the OSCCON) My understanding of it is that because the pulsein is "narrower" than when the osc is running at 4mhz the timings for reading IR signals is different.so "if stx<760" actually should be a different value. I am trying to understand the maths of what that value should be.
p.s. I know there is a typo in the code portb.4 is incorrect and I have corrected it in my actual code.

[BH_epuk]

ok i'm sure youve checked this but have you checked the ports Analog input is turned off.


ANSELA = 0
ANSELB = 0
ANSELC = 0 ' Config A2d All OFF