NEC protocall decoding with microcontroller

Thread Starter

embedtechnology

Joined Dec 25, 2015
42
Hi every one.
I want to decode nec code from the remote hand set mentioned the file bellow.
I experimented on it for months and came to know about it's command code for each key.
I have mentioned the code I found in my experiment on every key in HEX in the image
of the hand set but I have doubt whether those are write or wrong. Please any one help me
to know the truth. Thank you.code.png
 

Papabravo

Joined Feb 24, 2006
21,225
So what is the vendor code that goes with each key? They might not be the same for all keys. I can't tell you if they are right or wrong, but I can tell you that your information is incomplete. What are you using for a receiver? What are you using for a microcontroller?
 

ErnieM

Joined Apr 24, 2011
8,377
I did something like this a few years back for giggles. I used an IR receiver module (possibly from Radio Shack of all places) to convert the light into digital pulses. Then I used an oscilloscope to get the pattern send for each key.

Sorry, I kept no notes and have no recollection beyond that, but it's a good general way to get started. Once you know the key codes you can start on some program code to capture the key strokes.

Ultimately I got the button's name to display on an alphanumeric LCD display. It was one of the few times my techie toys actually impressed my wife.
 

Thread Starter

embedtechnology

Joined Dec 25, 2015
42
Thanks a lot ,
Actually I want this hand set to implement in my project named REMOTE CONTROLLED
ELECTRIC SWITCH BOARD . It 's a microcontroller based project.I all ready made it
with RC5 type remote but physical size of RC5 hand sets available in the market are so much
bigger than that of this tiny hand set. so I am interested to decode it's 32 bit code.I have also
deep knowledge in nec coding and decoding technology but I don't know the key codes. So
I experimented with a mic.and 8 leds to it's port With repeated attempt I found those key codes
that I already printed on each key in previous image. After searching through internet I could not
find any vendors for this remote because I don't know about the manufacturer .It is not mentioned
on the device.Normal information on nec key code available in internet are somehow different from one
another. So I confused. I hope that U understood my problem.
 

Papabravo

Joined Feb 24, 2006
21,225
What you need to do is read all 32 bits from the remote. What I called a vendor code is also called the ADDRESS field. It's purpose is to expand the set of buttons that can be handled. You would expect the ADDRESS and it's complement to be the first 16 bits, followed by the command and it's complement in the second 16 bits. I did the decoding by using the input capture feature and measuring the period between edges. The IR receiver took care of demodulating the 38 kHz Carrier.
 

Thread Starter

embedtechnology

Joined Dec 25, 2015
42
I know, but I want command code only. I must ignore address code. Capturing 32 bits is
not my headache. Moreover my headache is what is the command code for each key?.
Here is an example. In case of a rc5 remote, suppose you press volume+ button on the
remote hand set, then certainly it will emit 10 hex(16 dec. ,01 0000 bin) as command code along with
5 bit wide address code. In case of said nec hand set, the width of command code must be 8 bit instead.
what will be the volume+ command code? and this is my question.
 

Papabravo

Joined Feb 24, 2006
21,225
It should have leading zeros. If it was me I would also decode the address to prevent other remote with different address codes from aliasing for your remote. Ever been in a place with 5 or 6 remotes? It gets a bit chaotic.
 

hexreader

Joined Apr 16, 2011
581
Whilst Sony and RC5 have standard button codes, there is no standard NEC code for vol+ as you seem to think,

I suspect that your question cannot be answered unless somebody happens to recognise that exact remote (or some kind of equivalent) and happens to have decoded it.

A scope and logic analyser may be required to give a sure indication of your remote's IR protocol and coding.
 

Thread Starter

embedtechnology

Joined Dec 25, 2015
42
Thank you hexreader, your answer is really satisfied me.I programmed a micro controller
to decode nec code and after capturing 32 bits, I took up only command and ~ command
bytes . After comparing the two complementary command byte , I send the final command
byte to port_1 of the micro controller to which I connected 8 leds. I read the code from the
bineary bit pattern of that leds. I repeatedly pressed a same button and got same result
for each press.This test procedure was going on for every key and at last i came to a conclusion.
Those key codes I printed on every key in the image of my first post. Am I far beyond the real code ?
or am I little beyond it? or am I at the real code? Tell me please.
 

hexreader

Joined Apr 16, 2011
581
Sounds like you are doing all the right things. My guess is that your key codes are probably correct.

The fact that no code is repeated is a good sign too.

I would take it that you have decoded correctly,
 
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