Data processing in array

[Ioannis]

The more I observe your code and way of thinking, the more I see its briliance.

Thank you again Richard,
Ioannis

[richard]

a couple of ways

pulsetrain:  
index=67 
while index
while  !portb.0 :wend   ;wait for hi
index=index-1
pauseus 600                  ;bit period=3*te ie 3*400=1200uS
code.0[index]= ~ portb.0      ;sample @midpoint of bit period
while  portb.0 :wend    ;wait for lo
wend

;or with some simple time supervision

fail var bit
timer var word ext
@timer = TMR1L
PRELOAD CON 65535-820  ;@8MHz  timer prediv 2  each tick=1uS




pulsetrain:  
index=67 
t1con=0
fail=0


while index
timer=preload
while  !portb.0 :wend   ;wait for hi
t1con=$21
index=index-1
pauseus 600                  ;bit period=3*te ie 3*400=1200uS
code.0[index]= ~ portb.0      ;sample @midpoint of bit period
while  portb.0 && !pir1.0 :wend    ;wait for lo
t1con=0
fail=fail | pir1.0
wend

or sample @50,250,450,650,850 uS past transition to hi
where valid result is
11000 for a 1
11110 for a 0

there are endless methods

[Ioannis]

My simple thinking lead me to this version ditching the big array:

    index=0 
pulsetrain:                   'now collect 66 pulses ~800/400 ìsec
    pulsin portb.0,1,temp1
    if temp1<55 then main
    if temp1>170 then main
    if temp1<130 then
        code.0[index]=1
    else
        code.0[index]=0
    endif
    index=index+1
    if index<66 then pulsetrain

And then came your masterpiece of coding with TMR1...! Amazing!

It just needs to be reversed (the code array) I guess. No big deal.

Thanks,
Ioannis

[richard]

In a noisy environment you can over sample a bit to be sure of data validity, i expect the serial data from a keeloq
chip to be quite clean so a single sample point would suffice

sample @50,250,450,650,850 uS past transition to hi
where valid result is
11000 for a 1
11110 for a 0

sample var bitfail var bit


fail=0
pulsetrain:
index=67 
while index && !fail
while  !portb.0 :wend   
pauseus 50               ;50
if   !portb.0 then  fail = fail | 1
pauseus 200              ;250
if   !portb.0 then  fail = fail | 1
pauseus 200              ;450
sample=portb.0
pauseus 200               ;650
if   portb.0^sample then  fail = fail | 1
pauseus 200               ;850
if   portb.0 then  fail = fail | 1
index=index-1

code.0[index]= !sample

wend

[Ioannis]

In general the data stream on a good signal level is very clean. But when there is no RF signal, the radio module will produce a lot of noise that is converted to random pulses through the data slicer. This creates a lot of bad data and false triggers on a non rolling code systems if digital filtering is not applied. With the keeloq encryption it is safe to assume that such triggers will not happen. The probability to have 66 bits in a correct timing and also in the correct sequence, not mentioning the other safety measures of keeloq like counter etc, is really low if not zero.

When you referred to 5 sampling points I was thinking of timers etc to maintain a fixed sampling point in time...

Your code showed the application of KISS in a fine way!

Thank you for your great ideas,
Ioannis

[richard]

The probability to have 66 bits in a correct timing and also in the correct sequence, not mentioning the other safety measures of keeloq like counter etc, is really low if not zero.

i would not expect to ever receive a malformed bit from a keeloq serial stream , the data may be useless however.
single point sampling should be ok imho

[Ioannis]

Agree.

Though I have checked various implementations of RF remote controls and many have wide tolerances from the specified timings.

I am very much sure that those chips are bad copies of the original Microchip one. But are out there... If interested, I have many test of original and copy chips with the timings in excel file.

Ioannis