Send and receive

[fellnerse]

Hey,

I got a question regarding sending and receiving with the same device. I recorded a few commands with a IR-receiver and now I tried to see what happens if I send the same signals back. For that purpose I used the send and receive examples and merged them in one program. I also connected the input and output Pins with a cable. But somehow the receiver prints a completly different code than I'm sending. Is there a problem with my setup? What am I doing wrong? Does this even work? Or should I use two different devices because of timing issues?

Thanks in advance! Real cool project

[crankyoldgit]

Is there a problem with my setup?

Probably, but most likely with the software you've written/merged.

What am I doing wrong?

Typically, the problem is sending at the same time as receiving. You can get a feedback loop of sorts, or distorted captures. Or you could be trying to send UNKNOWN signals. We can't tell what it is you're doing without seeing your code.

If you want to see how to do it, look at:
https://github.com/crankyoldgit/IRremoteESP8266/blob/master/examples/DumbIRRepeater/DumbIRRepeater.ino
or
https://github.com/crankyoldgit/IRremoteESP8266/blob/master/examples/SmartIRRepeater/SmartIRRepeater.ino

Does this even work?

Yes, but you have to do it correctly. Read the comments in the code examples I linked.

Or should I use two different devices because of timing issues?

No and Yes. Mostly No. Read the comments. Unless you are isolating (physically visible) the transmitter from the receiver, you could corrupt your capture. If you have done that, you can capture and send at the exact same time. If not isolated, you typically need to stop the capture while you send, and resume afterwards.

Capture happens in the background via interrupts. It will take some CPU cycles, but not much. So, there is a very small chance the outbound transmission could have it's timing affected ever so slightly if capture is enabled, but it's unlikely to make a significant impact. However, if you truly need near perfect, or perfect transmission and capture at the exact same time, you need to run the processes on separate CPU cores (e.g. ESP32) or multiple ESP8266s.
Note: Almost no-one needs that level simultaneous send/receiving or accuracy.

[crankyoldgit]

Im actually not too sure but it looks like this: url

That's a demodulator. Two pins = diode, three = demodulator. Typically.

[crankyoldgit]

I'll try explaining it another way.
This library is for sending a frequency modulated IR signal. Such that a correctly existing IR receiving circuit (e.g. a TV) can accept it as of it was sent via a remote.

For this library to decode an IR message, it requires a hardware IR demodulator to demodulate the signal before it reaches the ESP etc.

Setting the use_modulation parameter to false, you can make the ESP generate an unmodulated signal when sending. That is typically useless when transmitting via IR, but precisely suitable for your oddball application.

[fellnerse]

Thanks, this makes sense to me now.
Anyone trying to do a similar thing should bear in mind that different voltage levels can be a problem.
I had to switch from a 3.3V microcontroller to a 5V microcontroller as the device I want to control runs the IO pins with 5V. Usually 3.3V should be enough to trigger 5V IO pins, but in this case somehow it was not.

[crankyoldgit]

Or you could have used a voltage level shifter, or a simple transistor to switch/shunt a 5v line in the circuit. Eg. Like our suggested transmission circuit diagram.

I.e. an NPN transistor between the Vin & DATA of the IR demodulator, controlled by the ESP.

[fellnerse]

I actually tried using an NPN transistor but with Vin of the ESP..this did not work (probably some wiring issue). I could have tried using the Vin of the IR demodulator you are right....did not try it, because I always use the other ESP for receiving the signals and verifying it works.

But thanks for the tip, I will try with the said circuit again!

[fellnerse]

Aah ok I get it now.

…

On Tue, 29 Jun 2021, 10:11 David Conran, ***@***.***> wrote: Im actually not too sure but it looks like this: url <https://www.reichelt.de/de/de/ir-empfaenger-module-38khz-90-side-view-tsop-31238-p107210.html?PROVID=2788&gclid=CjwKCAjwieuGBhAsEiwA1Ly_na0tAVTaV9xlQF-TxJXRmjABcsTSxH-Ku45Ix5NQ2bhv3e1VxGkbLhoC430QAvD_BwE&&r=1> That's a demodulator. Two pins = diode, three = demodulator. Typically. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1511 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AJ2CVCH3BBWR4KUD4VBJVOLTVF52BANCNFSM47NXNDFA> .