NEC IR Protocol remote decoder, help me before I kill myself!

[bogdan]

the code was for a samsung tv .... close, but not the same like the nec protocol

SAMSUNG IR protocol:
http://www.samsung.com/global/busine...000_090108.pdf (check "Figure 1. IR Signal")



NEC IR protocol:
http://www.mcselec.com/index.php?opt...=223&Itemid=57

... the leader/header for nec should be 9msec

change the
DEFINE PULSIN_MAX 990 (try with 10% deviation... 900*1.1)
- - - - - - - - - - - - - - - - - - - - -
IF (Header < 810) OR (Header > 990) THEN GOTO IRIN (again the -/+10% deviation)

[Bonxy]

I've looked at the nec ir protocol but i'm non the wiser :-(

Just if anyone is interested I have attached the actual code that came with my remote and reciver IC kit, it was written for the arduino and commented in japanese, I have translated the comments to english but I cant translate the code, if anyone wants to look at it it might reveal to someone more experienced what I need to do to get it to work maybe ?.

[Jumper]

Plan B:

Use an other pic and set up the HPWM manually for 38 kHz. Then you connect an IR diode to the HPWM pin using a resistor to get aprox 20 mA in the led.

Then in the code you make a simple main loop. Turn on the HWPM, delay 9 ms, and then turn off the HPWM, wait a while (i.e 5 ms) and then goto main again. Point this led towards the ir-receiver from a close distance and now you have a signal that you really know how it looks like. Then you put a shoebox upside down over both the receiver and the transmitter led so they get a nice dark space to be in.

Have you ever thought about catching the IR signal using the CCP module or by using interupts and a timer?

This way you can even build a text signal for the NEC protocol ... [startpulse] delay [bit0] delay etc..

Which way to decode the signal is the best? Well it all depends what other things your pic will do. If it will only decode the IR signal you can just read the pin in a fast loop and increment a counter when it is LOW.

Keep in mind that the receiver you are using is ACTIVE LOW.. so the pin will be high when there is no modulated IR light present.

[dhouston]

NEC IR protocol:
http://www.mcselec.com/index.php?opt...=223&Itemid=57

Here's a more authoritative source for the NEC protocol...

• http://davehouston.org/Nec6121.pdf

[Bonxy]

Thanks dhouston, but looking at more protocol descriptions is just giving me headache lol, I've been at it all week, I think I've actually looked at the description before when I was first googling the nec protocol.

What I need is a simple working code example that I can then develop...

If you or anyone can give me a code example for a 18f4550 at 4 or 20 mhz i would be extreemly gratefull..

Thanks guys

[cncmachineguy]

the code was for a samsung tv .... close, but not the same like the nec protocol

SAMSUNG IR protocol:
http://www.samsung.com/global/busine...000_090108.pdf (check "Figure 1. IR Signal")



NEC IR protocol:
http://www.mcselec.com/index.php?opt...=223&Itemid=57

... the leader/header for nec should be 9msec

change the
DEFINE PULSIN_MAX 990 (try with 10% deviation... 900*1.1)
- - - - - - - - - - - - - - - - - - - - -
IF (Header < 810) OR (Header > 990) THEN GOTO IRIN (again the -/+10% deviation)

Did you try this?

[Bonxy]

cncmachineguy

Yes I did, i still did not get valuses to match, I got values in the range of 552 to 614 and everything in between.

[bogdan]

please let us now the model # of the remote

(i will try to upload the codes into a universal remote and i will check the protocol later today)

[Bruce]

There are much better/faster ways to do this, but this should get you started with something that's fairly easy to understand.

Assuming you have an NEC transmitter that outputs something like the top portion of the graphic below;

This should return similar results to what's shown in the serial terminal window just above.

#CONFIG
  __config _XT_OSC & _WDT_ON & _MCLRE_OFF & _LVP_OFF & _CP_OFF
#ENDCONFIG
 
DEFINE OSC 4
 
Leader VAR WORD     ' will be up to 900 for a 9mS leader pulse
BtnVal VAR BYTE[32] ' holds 32 pulse results
DByte1 VAR BYTE     ' address byte
DByte2 VAR BYTE     ' inverse of address byte
DByte3 VAR BYTE     ' command byte
DByte4 VAR BYTE     ' inverse of command byte
X      VAR BYTE     ' loop count
 
Main: 
  PULSIN PORTB.0,0,Leader  ' leader pulse is ~9mS low-going
  IF Leader < 850 THEN Main
 
  FOR X = 0 TO 31          ' grab 32 incoming pulses
      PULSIN PORTB.0,1,BtnVal(X) ' now measuring high-going pulse widths
  NEXT X
 
  ' now we'll decode 4 bytes from 32 pulses
  FOR X = 0 TO 7               ' sort 1st 8 pulses
      IF BtnVal[X] > 150 THEN  ' > 150 x 10uS = > 1.5mS pulse period
         DByte1.0[X]=1
      ELSE
         DByte1.0[X]=0
      ENDIF
  NEXT X
 
  FOR X = 8 TO 15              ' sort 2nd 8 pulses, etc....
      IF BtnVal[X] > 150 THEN
         DByte2.0[X-8]=1
      ELSE
         DByte2.0[X-8]=0
      ENDIF
  NEXT X
 
  FOR X = 16 TO 23
      IF BtnVal[X] > 150 THEN
         DByte3.0[X-16]=1
      ELSE
         DByte3.0[X-16]=0
      ENDIF
  NEXT X
 
  FOR X = 24 TO 31
      IF BtnVal[X] > 150 THEN
         DByte4.0[X-24]=1
      ELSE
         DByte4.0[X-24]=0
      ENDIF
  NEXT X
 
  HSEROUT [BIN8 DByte1,13,10,BIN8 DByte2," Address",13,10,13,10]
  HSEROUT [BIN8 DByte3,13,10,BIN8 DByte4," Command",13,10,13,10]
  PAUSE 1000
  GOTO Main

[Bonxy]

Bruce, thanks for uploading that code, I am going to try the code on my next day off work and will report back, I've had a look and its well commented and I can understand it, so I have fingers crossed that it's going to work :-), I think where I am falling down is my poor understanding of math, eg the osc speed and its relation to ms's & pulsin, I just dont get that, anyway I'm going to give your code a good go, thanks again.

Bogdan, I have attached my remote pictures & instruction PDF that came with it, thanks also for your help with this :-)

[Ioannis]

I think where I am falling down is my poor understanding of math, eg the osc speed and its relation to ms's & pulsin

Look at post #8. Also the manual at the Pulsin command explains why is that.

Ioannis