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gl17
Joined: 23 Jul 2013
Posts: 2
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| pic12f1822 decoding holtec code |
 Posted: Tue Jul 23, 2013 2:17 pm |
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Hi all.
I have a pic12f1822 (with internal RC osc) board with a signal line connected to PIN_A3
I need to decode holtec HT6012 transmitter code.
it looks like so (first 250us "П" pulse is synchro, others are data)
Additional problem - it's a radio channel, and without transmitting it looks so at pin_A3 (sorry haven't good oscilloscope at home) (bottom - transmitter works)
I tried to do it using timer1 directly, like so
| Code: |
//setup_timer1=1us
//call checkCode after first pulse
unsigned int32 checkCode(void)
{
unsigned int8 lastState = 0;
unsigned int8 i;
unsigned int32 code;
unsigned int16 timerValue;
int1 state;
state = 0;
putc(0x66);
while (1) {
if (get_timer1() > 0x1388) {code = 0xA0000000;break;} // >5ms are passed
if (input(IN) != state) { //PIN state changed
timerValue = get_timer1();
set_timer1(0);
state = !state;
i++;
if ((timerValue > byte_time_low0) & (timerValue < byte_time_low1)) {
// lastState = 0: none, 1: _--250, 2: __-500 ,3: -_250 , 4: --_500
// in hex == { 0, 1, z } trinary state of pin
// __-__- 1 _--_-- 0 __-_-- z
// == 11, 00, 01 half-bits in transmission (LSB 1st)
if (state == 1) { //1: _--250
if (lastState == 0) {lastState = 1;}
else {code = 0xA0000000;break;} //bad code
}
else { // state == 0 //3: -_250
if (lastState == 0) {code = 0xA0000000;break;} //bad code
else {
if (lastState == 2) {
lastState = 0;
code = (code << 1) | 0x01; //
} //good code
else {code = 0xA0000000;break;} //bad code
}
}
}
else {
if ((timerValue > byte_time_high0) & (timerValue < byte_time_high1)) {
if (state == 1) { //2: __-500
if (lastState == 0) {lastState = 2;}
else {code = 0xA0000000;break;} //bad code
}
else { // state == 0 //4: --_500
if (lastState == 0) {code = 0xA0000000;break;} //bad code
else {
if (lastState == 3) {
lastState = 0;
code = (code << 1) | 0x00; //
} //good code
else {code = 0xA0000000;break;} //bad code
}
}
}
else { // bad byte time
code = 0xA0000000;break;
}
}
}
if (i==49) {break;}
}
return code; //error if timeout, or error time_packet, or error packet len
}
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it doesn't works, looks like i don't have enough time between pulses.
and i'm feeling i'm doing something really wrong
any ideas how to solve it briefly and elegant ? |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Jul 23, 2013 5:12 pm |
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HOLTEC decoder IC interfaced to pic?
these have limiters/ signal cleaner circuit and barrel shiffter. |
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gl17
Joined: 23 Jul 2013
Posts: 2
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| Posted: Tue Jul 23, 2013 6:22 pm |
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no additional IC's (
signal from RF circuit goes directly at pin |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Tue Jul 23, 2013 7:12 pm |
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best of luck with the recovered signal  |
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gpsmikey
Joined: 16 Nov 2010
Posts: 588
Location: Kirkland, WA
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| Posted: Tue Jul 23, 2013 11:10 pm |
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Without a decent front end to recover that signal, I think you are for an exercise in frustration - the old "garbage in - garbage out" applies here with a signal that looks that ratty.
mikey
_________________
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3 |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Wed Jul 24, 2013 8:42 am |
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BTW: 40 years of my career has been involved with RF .
and the recovered signal you show looks for all the world like its either :
1- unfiltered direct conversion output, with low signal input
or
2- heterodyne IF system well below limiting
or
3- slight frequency mismatch between TX and your RX
And on second thought , even the Holtec receiver chip will not be of much use with that signal as an input.
Either way , you will find no joy as you attempt reliable data recovery.
Your RF link is way too crappy, and no PIC code is gonna make it right.
you can take it to the bank .
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