I would like to try to make a remote to activate audible pedestrian signals.
In my country, nearly all pedestrian signals can generate sounds for blind people. To activate the speakers, the blind person need a remote sending an hexadecimal code at 868,3 mhz of frequency. I'm a traffic signals collector, and so I would like to be able to activate these speakers.
Alas, these remotes are quite expensive (around 70 to 100 dollars). Which I think is quite high for something like this.
Do you think it could be possible with Arduino ? Unfortunately, I don't know much about this subject.
I thought I'd use an arduino nano and an 868 mhz radio transmitter to send this hexadecimal code repeatedly as long as I keep a button pressed.
Official documentation about it :
"The command protocol consists of :
-A header including :
A preamble. The preamble lasts for 2 square signal periods (total duration 830 Ī¼s).
Synchronization
A 24-bit hexadecimal code. This code is 00A388.
The message is repeated as long as the remote control button is pressed.
Each character is coded on 4 bits.
The least significant bits are sent first. The transmitted code is therefore 388A00.
The value 3 = 0011. As the least significant bits are sent first, 1100 is actually sent. Similarly, value A = 1010 > code sent 0101."
That should be straightforward. Any 868 radio module should work, if it is capable of being operated in ASK (Amplitude Shift Keying) or OOK (On Off Keying) mode and can be tuned to the correct frequency, e.g. the RFM69 series. Here is one assortment of radio modules.
Please post a link to the entire technical document so that the signal timing can be verified. The diagram is not completely clear.
I googled trying to answer a question I have, and found a thread where I am incompetently trying to help in a similar situation.
The question is: can the RFM69 be set up to be used in the same manner one would use a cheap pair of 433 or 315 modules, the kind with just four connections to be made: antenna, power, data (in or out) and ground?
Made dumb, basically. For the OP's project, a dumb radio set would be straightforward.
On the other hand, or is it the same hand, is the RFM69 so flexible that it can be set up to fake any protocol that is documented as here, or reverse engineered?
Yes, but you have to use SPI communications to put the radio in that mode, set the frequency, etc., so those connections are required as well. RadioHead can do that "automatically", as described in this article:
Understood. It looks like a good upgrade to cheap radio sets, and it would just be a matter of doing the setup, the rest of the code and wiring wouldn't know the diff.
And assuming setting it up for the same continuous mode as a transmitter would be as easy.
Which means such a module and RadioHead would be a good solution. Synthesizing the protocol should not be too hard.
The document is in french so I translate it, here it is :
"Features of the remote control activation system:
If the sound repeater is activated by remote control, it must be able to receive a command. The transmission characteristics are described in the following two sections. This activation is called an interoperability transmission link.
However, this mode of activation is not exclusive, and other means of transmission may be added. For example, the devices may include several other radio activations.
Technical characteristics of the interoperability transmission link :
The general characteristics must comply with the RTTE 1999/5/CE directive and the harmonized standards: prNF EN 300220-3 and prNF EN 301489-3. The transmission frequency must be centered on 868.3 MHz, and the signal will be transmitted in amplitude modulation at a power less than or equal to 25 milliwatts.
The command protocol consists of :
-A header including :
A preamble. The preamble lasts for 2 square signal periods (total duration 830 Ī¼s).
Synchronization
A 24-bit hexadecimal code. This code is 00A388.
The message is repeated as long as the remote control button is pressed.
Each character is coded on 4 bits.
The least significant bits are sent first. The transmitted code is therefore 388A00.
The value 3 = 0011. As the least significant bits are sent first, 1100 is actually sent. Similarly, value A = 1010 > code sent 0101."
Yes, it seems so. These are specifications for approved remote signaling devices. Obvsly they want to ensure that everyone plays nice; one way is to limit radiated power, another to limit total transmission duration.
There may be rarely levied but very serious fines for disobeying.
You should check to see if third party remote makers are required to get approval on a design-by-design basis from any controlling authority.
