How to receive multiple frequencies simultaneously through a sub1ghz chip? - Page 1
Forum section: electronics / rf-microwave

author: pdskill
author_rank: Newbie
timestamp: July 15, 2024, 01:59:23 pm
content: I have a remote control that can copy multiple frequencies, such as 433 MHz, 315 MHz, or other frequencies. When I disassembled it, I found that the main control chip and the RF chip were polished, so I couldn't identify the model through the markings. However, by examining the package, crystal oscillator, and the distribution of external capacitors and resistors, I deduced that the RF chip is a sub-1GHz chip produced in China with the code name CMT2300A. How is it possible to use a sub-1GHz chip to simultaneously detect multiple frequencies and copy signals from remote controls of various frequencies?

author: shabaz
author_rank: Frequent Contributor
timestamp: July 15, 2024, 03:27:56 pm
content: Curious why the photo has silkscreen labeling hidden by you. What's the reason? Secondly, do you require the information for a legal purpose? Given that it looks like a device for rolling codes.

author: radiolistener
author_rank: Super Contributor
timestamp: July 15, 2024, 04:55:01 pm
content: Quote from: pdskill on July 15, 2024, 01:59:23 pmThis is very easy, just use several frequency down converters feed with different frequency and get as many simultaneous frequency reception as you want.There is also more simple and cheap way, just scan several frequencies every 0.1 sec and when a carrier is detected on one of the scanned frequencies, simply start recording it. In that way you can done it just with one mixer.

author: tggzzz
author_rank: Super Contributor
timestamp: July 15, 2024, 05:39:16 pm
content: Quote from: shabaz on July 15, 2024, 03:27:56 pmPrecisely.The near-duplicate posting is also suspicioushttps://www.eevblog.com/forum/beginners/a-question-about-the-implementation-of-multi-frequency-copy-remote-control/msg5573751/#msg5573751

author: pdskill
author_rank: Newbie
timestamp: July 15, 2024, 05:56:48 pm
content: Quote from: tggzzz on July 15, 2024, 05:39:16 pmThis is my first time using this forum, so I don't know which section to post to.Quote from: tggzzz on July 15, 2024, 05:39:16 pm

author: pdskill
author_rank: Newbie
timestamp: July 15, 2024, 06:01:28 pm
content: Quote from: radiolistener on July 15, 2024, 04:55:01 pmIf I only use one, how should I ensure that every transmitted frequency can be received? I have tried the method of cycling the frequency, but it cannot guarantee that every transmitted signal can be received.

author: tggzzz
author_rank: Super Contributor
timestamp: July 15, 2024, 07:11:27 pm
content: Quote from: pdskill on July 15, 2024, 05:56:48 pmDouble posting is always annoying, on any forum, and has been for the past 40 years.Do you have any responses to the questions from shabaz?

author: radiolistener
author_rank: Super Contributor
timestamp: July 16, 2024, 12:42:44 am
content: Quote from: pdskill on July 15, 2024, 06:01:28 pmFor remote control you can guarantee that every signal will be received, because remote control uses slow data transmission. The only exception is when two remote control sending packet simultaneously on different frequency, only one can be captured in that way.

author: ozcar
author_rank: Frequent Contributor
timestamp: July 16, 2024, 04:47:08 am
content: Years ago I looked at some other remotes (which have no display on them) made by the same manufacturer.They were based on an STM8L micro, a TI CC110L and what I think is a switch for changing bands (AS193). May not have been "genuine" chips, but they had made no effort to remove markings on them. Mentioned here:https://www.eevblog.com/forum/chat/universal-fixed-and-rolling-code-remote-control-duplicator/I know nothing about CMT2300A, but presumably you could figure out what they do by peeking at the chit-chat between the micro and the RF chip. I did that on one of the remotes I had and could see that in receive/copy mode they stepped through frequency with bandwidth quite wide and then reduced the bandwidth to hone in once they saw a signal.I noticed that when "copying" a remote which transmits in sequence on three different frequencies in the same band (supposed to make it more resilient to interference), the copy transmitted on very close to the correct frequencies. However, given that they have to figure out the brand/model of remote in order to get the code right, I suspect that perhaps they did not actually manage to measure the three frequencies so accurately, but rather said "Aha, this is model xxx remote, which we know uses frequencies x, y and z".