PIC Beginner - Infrared Receiver and IR Protocol

[dhouston]

From your schematic it appears you are using an IR receiver. Which one?

IR receivers usually are active low while the code I supplied for the NEC protocol was for RF where the receiver is active high. Also, my code was meant to work with the RF transmitter code that accompanied it which used slightly different timing than the NEC IR protocol.

The EDN article is wrong about details of the NEC IR protocol. It is explained in this NEC datasheet.

• http://davehouston.org/Nec6121.pdf

You will need to modify my RF code in order to receive/decode IR codes.

'12F629

@ __config _INTRC_OSC_NOCLKOUT & _WDT_OFF & _MCLRE_OFF & _CP_OFF

DEFINE PULSIN_MAX 1140				'>1140 RETURNS 0
DEFINE DEBUG_REG GPIO
DEFINE DEBUG_BIT 2				'GPIO.2
DEFINE DEBUG_MODE 1 				'Inverted
DEFINE DEBUG_BAUD 9600
DEFINE OSCCAL_1K 1

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

        CMCON = 7                   'comparators off
        Debug "IR NEC PROTOCOL"
init:   IR[0]=0:IR[1]=0:IR[2]=0:IR[3]=0:i=0
        PulsIn GPIO.1, 0, stx	
        If (stx<760) Then init  		
        'debug #stx                 
        While GPIO.1=1:Wend			'wait space
        Repeat
          PulsIn GPIO.1, 1, pulse
          If (pulse>100) Then
            IR.0(i)=1				'set bit
          EndIf
          i=i+1 
        Until (i>31)
        For i = 0 To 3
          Debug IHEX2(IR[i] REV 8)
        Next
        GoTo init

        End

I have not tested the above code (I don't have time to build a circuit with an IR receiver.) and you will need to convert it for your PIC and the pins you are using.

Note also that my code does not deal with the NEC shortcut repeat code.

[dhouston]

Change...

        For i = 0 To 3
          Debug IHEX2(IR[i] REV 8)
        Next

to...

        For i = 0 To 3
          Debug IHEX2 IR[i]
        Next

The bit order is already reversed as the bits are set by...

RF.0(i)=1

[lester]

Moe, you might want to read this article: Controlling the world from your armchair

[lester]

Moe, Infrared remote control decoding maybe considered something of a black art, however, this tutorial will show you that its principals are quite straightforward, and easy to implement on a PIC microcontroler.

Thanks to BASIC’s shallow learning curve, software designs that used to take weeks can now be realised in a just few hours. This article presents software solutions in the PicBASIC Pro language.

You might want to read the article: Controlling the world from your armchair

[lester]

The article is an extract from the book, EXPERIMENTING with the PICBASIC PRO COMPILER, written by Les Johnson.

The book is cuerrently out of publication, however we are considering publishing an online version as part of the new PIC BASIC portal that we are developing to support PIC BASIC Users.

[komoe01]

dhouston,
When I change code, old result 0 turn to 255. All the keys press are same.




Header Logic 0 Logic 1 Logic 1 logic 0

2400 600 600 600 1200 600 1200 600 600
x a b c d e f g h i j
+------------------------+ +------+ +--------------+ +--------------+ +------+
| | | | | | | | | |
| | | | | | | | | |
| | | | | | | | | |
---+ +------+ +------+ +------+ +------+ +------
x____________________________|_____________|______ _____________|___________________|_____________|
pulsin header 1st loop 2nd loop 3rd loop 4th loop

return width of length





-- code start -------------------------------

          
         pulsin irIn , 0 , Header       'Line 1
    
            for i =0 to 3
               pulsin irin, 0 , tmp       'line 3

               if tmp > 90 then                
                    body.0[i] = 1         'line 5 
               else
                    body.0[i] = 0         'line 7  
               endif
            next

-- end of code -------------------------------

I think pulsin work as follow:

1. pulsin is timeout when no rising edge was found. return width is zero.
2. pulsin is time out when rising edge was found and then until falling edge. return the width length.


so pulsin in code run like that:


Line 1 : pulsin start measure (x) to end edge (b). Width is (a) to (b) so Header = 2400 (space (x) to (a) is not count.

Loop 0 (1st loop)
Line 3 : pulsin start measure (b) to end edge (d). Width is (c) to (d) so tmp = 600 (space (b) to (c) is not count.
Line 5 and 7: see the width lenght (not space) and decided logic 0
Loop 1 (2nd loop)
Line 3 : pulsin start measure (d) to end edge (f). Width is (e) to (f) so tmp = 1200 (space (d) to (e) is not count.
Line 5 and 7: see the width lenght (not space) and decide logic 1
Loop 2 (3rd loop)
Line 3 : pulsin start measure (f) to end edge (h). Width is (g) to (h) so tmp = 1200 (space (f) to (g) is not count.
Line 5 and 7: see the width lenght (not space) and decide logic 1
Loop 3 (4th loop)
Line 3 : pulsin start measure (h) to end edge (j). Width is (i) to (j) so tmp = 600 (space (h) to (i) is not count.
Line 5 and 7: see the width lenght (not space) and decide logic 0

PULSIN can only measure the width length.

When this code is used for NEC Protocol, all pulse are equal depending upon if statement (Logic 0 or 1)
Because In NEC, logic 1 or 0 is determined by space length. How can I measure space with pulsin.

lester
Thanks.

I already read Les Johnson's article and "Section 6: Experimenting with Remote Control" of that book. I already tested it. All are ok. But it's Sony IR Protocol (Pulse Width Modulation) that quite different from NEC IR Protocol (Pulse Distance Modulation).
I admire you and dhouston when I found your join date.
I start and learn picbasic at last week of July of this year. I search and collect PIC books (picbasic, C and Assembly) and article. I found about 60 books and articles. But I cannot find enough explanation for a command. eg. I want to know pulsin in detail. How pulsin work? examples relating pulsin. Pulsin in "PicBasic Pro Manual" is general. Picbasic is best language for me although I've little experience with C Language.


Moe

[komoe01]

Sorry sample wave is broken.



If wave picture is not found, Please see it in attachment picture

Moe

[dhouston]

When I change code, old result 0 turn to 255. All the keys press are same.

It works fine for me. It's impossible for me to guess at what changes you have made to it. Try to test it using my code exactly as written. Once that works, try modifying it for your application, going step by step to isolate where the problem is being introduced.

The waves you've attached (including the second one) are not NEC IR protocol.

How are you sending the IR codes?

[komoe01]

dhouston

The wave image is a sample (part of the sony protocol).

Try to test it using my code exactly as written.

Ok. dhouston

But 12F629 pic is not available for me. Just a few PIC model can buy in my country. I have to use 16F84A or 16F628A. Beside I use IR, not RF.
I'm a beginner for pic so I've not familiar with DEBUG that used in your code.

So I write code to PIC than I see the result of LED signal and Computer program.

When I test it using your code exactly, what can I see the result from where? Can I use Infrared remote control? or I must built your transmitter to test receiver.

I think I must to change some code.

I do my best as you say!

Thanks.

Moe

[tr6coug]

Lester, is there somewhere we can download the include files from the book? I'd like to use the Sony IR files in a project. Thanks!

The article is an extract from the book, EXPERIMENTING with the PICBASIC PRO COMPILER, written by Les Johnson.

The book is cuerrently out of publication, however we are considering publishing an online version as part of the new PIC BASIC portal that we are developing to support PIC BASIC Users.

[amenoera]

dears ,

i know its a very long time , but please am stick on this , can you post a full working code for pic16f84a to decode nec protocol .
many many thanks .