Sharing a Serial Connection

Projects General Guidance
1

Hi.

I was wondering if it was possible for two or more Arduinos to share an external sound module via Serial?

I am creating some modules to handle various jobs in a campervan. I want them to play sounds abd voice messages but, I would rather not have each module have it's own sound module.

They send a message to the sound module through serial, would it be possible to connect them all to the module?

None of this is safety critical, no gas leak or Co2 warnings or anything like that.

Thank you in advance for your time.

Paul

2

Which Arduinos and which sound module(datasheet)?

3

Use a bus or network connection.

4

Any Arduino basically. I use Uno, Mega, Nano and Micro depending on the application..

The module is a DY-SV8f.

Here is a link to the data sheet.

5

I can't i'm afraid.

The way I use the module, it has to be serial.

6

What's the probability that Arduinos will send a message to the module at the same time?

If that risk is acceptably small, just connect the cathode of a diode to the TX pins from each Arduino and connect the anodes to the Rx pin of the module, adding a pull-up resistor to the Rx pin.

If course, there's a good chance that 5V serial signal won't work over the distances and environment of a camper van.

7

Thank you for the advice, much appreciated.
Unfortunately, that's the the first thing I tried and it didn't work.

The signal gets to the module just fine via the diode however, there is no signal at all as soon as I attach the second arduino and diode.

I tried it with the three different types of diode I had but none worked unfortunately.

Thank you for trying though.

8

It should work, so maybe you used the wrong kind of diode or connected them incorrectly.

Show us a diagram of how you wired up the diodes to the Arduino pin.

Do you know what type of diodes you tried? Post some close-up photos showing any codes printed on them.

9

I was surprised that it didn't work too.

The three types of diode I have are:
1N4007
1N4148
1N5819 (Schottky)

Here is a diagram of the way that I connected it all up.

Thank you.

Diagram

10

Reverse the diodes!

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11

You connected the cathodes to the Rx pin.

Not sure why that worked with the diode reversed like in your diagram. The idea is that any of the Nano Tx pins can pull the sound module's Rx pin low through their diodes, otherwise the pull-up resistor pulls the Rx pin high. It avoids connecting them directly, which would cause a short circuit.

That's what I'd use.

PS do you know how to draw a proper schematic? We prefer those! Hand drawn is fine.

12

Resistor shown as 100 Ohms. Should be 1k.

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13

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