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I have quite a few Radio Controlled Toys, Some I have hacked so that they become autonomous.

This gave rise to a question:
Can all Receiver (RX) and Transmitter (TX) chip be somehow made compatible with each other ? Say I have RX-2 and TX-2 chips. Can I use a remote from 1 toy to control the other. I read about RX/TX chips, they tend to have different frequencies, but if I can somehow get them to match their frequencies can I get them to work with each other? Is there anything else that I need to do?

All of that is quite a Mouthful so This is what I mean to ask:
Q.1) Is it possible to use RX / TX chips from two different toys together?
Q.2) If possible how can I do so?

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closed as too broad by Eugene Sh., Daniel Grillo, tcrosley, placeholder, PeterJ May 24 '16 at 23:19

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ This question is too vague. Which chips are we talking about? There is no such a part number "chip". \$\endgroup\$ – Eugene Sh. May 24 '16 at 17:36
  • \$\begingroup\$ @EugeneSh. I want to ask if any two chips can be made compatible, no two specific chips but any two chips. \$\endgroup\$ – Aaditya Sahay May 24 '16 at 17:37
  • \$\begingroup\$ Of course not.. \$\endgroup\$ – Eugene Sh. May 24 '16 at 17:38
  • \$\begingroup\$ @EugeneSh. Disappointed, I thought if I could somehow modulate the frequencies of both of them and matched them, it should do the trick. \$\endgroup\$ – Aaditya Sahay May 24 '16 at 17:40
  • \$\begingroup\$ Suppose one is a UART and the other is a USB PHY, then it wouldn't even make sense to "modulate the frequencies of both of them". \$\endgroup\$ – The Photon May 24 '16 at 17:46
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A lot of modern RC toys use 2.4 GHz chips originally intended for other purposes, such as wireless mice and keyboards. Generally each manufacturer of one of the original designs chose their own modulation and packet framing details uniquely - it would be possible to make a universal chip that handled all of those, though short of going to a software defined radio implementation it is not clear that there is anything currently on the market which does. Three major chips that have been used are the Cypress CYRF6936 type, the A7105 type, and the NRF24L01 type.

However, low-cost consumer electronics is a world of copycats, so the NRF24L01 style has received a lot of imitation - both in devices sold under legitimate differentiating brand names, such as from Beken or on modules from Hope, and also in falsely labelled counterfeits that are still generally, if imperfectly functional. Additionally, Nordic's BTLE SoCs can typically operate in an NRF24-compatible mode. And the XN297 part that has seen heavy usage in the past year has compatible on-air modulation, but some differences in framing and data handling.

Even when using using the same chip, there are often a number of differences in the protocol which different products use to transmit data over it. This covers questions such as when to hop to a new frequency, out of what collection, and how often to transmit. It also includes questions such as how the data from a given control function is encoded in a packet, and even basics such as which way a control actuator or electronic throttle should respond to which direction of control stick movement. Many products also have a process of "binding" during which transmitter and receiver agree on a set of frequencies or address codes to use with each other. But using inexpensive SPI logic analyzers, many enthusiasts have been able to reverse engineer these details and publish open source projects implementing compatible encoders or decoders, often for a variety of protocols in a single program. Typically this takes the form of an ATmega or STM32 connected via SPI to a generic RF module containing the required 2.4 GHz chip, but in a few cases the output is instead a serial stream to a more sophisticated RF module that implements details of the proprietary air protocol. The individual chipsets are inexpensive enough that more than few hobbyists have modified their favorite control transmitters to simply contain modules for each of the three major families, with software then covering the finer details.

In addition, some of the finer degrees of differentiation between semi-compatible chips have been figured out to the point where software can achieve compatibility. For example, it is possible via data manipulation to have a genuine NRF24L01+ or close compatible transmit in a way that can be received by an XN297, though it is not yet clear if the reverse will be true.

Obviously, what is used in a fast-evolving price-driven consumer market changes rapidly. There already seems to be a trend away from having a distinct radio IC connected to an MCU via SPI, towards integrating the radio and MCU functionality in the same part.

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  • \$\begingroup\$ Nice and Elaborate answer, thanks . I have removed the chip as of now and configured my micro controller to work with an IR based remote. \$\endgroup\$ – Aaditya Sahay May 25 '16 at 6:26
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"Q.1) Is it possible to use RX / TX chips from two different toys together?"

Maybe, if the two chips use the same protocol and frequency. In the old days, with 27 MHz radio controlled model planes and such, there was one dominant protocol and the only variation was the 27 MHz sub-band that was used, so exchaning a crystal ws often sufficient. But those days are long gone, and there are lots of cheap chips that implement different protocols.

"Q.2) If possible how can I do so?"

Most probably we couldn't, so you definitely can't.

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  • \$\begingroup\$ Say both of my toys used to work on 2.4GHz, will I still not be able to use them together ? \$\endgroup\$ – Aaditya Sahay May 24 '16 at 17:43
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    \$\begingroup\$ @AadityaSahay can you connect a Bluetooth device to a Wi-Fi network? or for that matter a microwave oven? All three use the same frequency (2.4GHz), but none of them can talk to each other. \$\endgroup\$ – Tom Carpenter May 24 '16 at 17:44
  • \$\begingroup\$ @TomCarpenter Well actually you can use a bluetooth device to connect to a Wi-Fi network but I get the point, Thanks \$\endgroup\$ – Aaditya Sahay May 24 '16 at 17:46
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    \$\begingroup\$ @AadityaSahay that's not connecting a Bluetooth device to a wi-fi network, that's connecting a wi-fi device to a wi-fi network and a Bluetooth device to another Bluetooth device. \$\endgroup\$ – Tom Carpenter May 24 '16 at 17:50
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    \$\begingroup\$ @Aaditya if the past is a prediction, 'they' will create 2 new and imcompatible protocols each time a chip reaches the market that can talk two existing protocols. ;) \$\endgroup\$ – Wouter van Ooijen May 24 '16 at 17:55

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