Why should one prefer using control chain connector over usb?

In the code of the pot example from the control chain arduino library i found the following comment:

There are two options to connect the Arduino to your MOD:
1. Using a Control Chain Arduino shield and an Ethernet cable
2. Using the regular Arduino USB cable

You should use the last case only in the development stage.

Why should one use the last case only in the development stage? What is the actual difference between the two? It would be very convenient to be able to try stuff also without the arduino shield.
The reason for me asking is that I’m interested in getting the library running on a teensy, which obviously isn’t compatible with the arduino shield.

Some explanation would be much appreciated!

Also. Some more details about the pinout and electrical specification of the rj45 connectors would also be much appreciated! This, in order to be able to implement a control chain connection without using a shield.



The shield allow you to create a chain of devices. By default the control chain daemon won’t be listening to requests coming from USB, but only the control chain port. In order to do that you’ll have to tweak the configuration file or run the process manually.

ssh root@
systemctl stop controlchaind
export LIBCONTROLCHAIN_DEBUG=1   # optional
controlchaind /dev/ttyXXX -f

Here is the pinout.

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@ricardocrudo Thank you for the reply!
I will elaborate on my thoughts and questions a bit.
I interpret the schematic as follows:
rj45 pin: arduino(mcu)

1: Arduino tx pin
2: Arduino tx pin inverted
3: Arduino rx pin
4: Arduino Vin pin (is the mod duo providing 12v out on this line?)
5: -"-
6: Arduino rx pin inverted
7: Common Ground
8: -"-
shield (if present): casing (ground)

Have I understood this correctly?

Is it necessary to connect Vin? I was thinking of powering an mcu from the usb port and leave pin 4 & 5 unconnected.

Is it necessary to use inverted signals on serial pins if the distance is gonna be small? How about skippping pin 2 & 6 for a 20 cm cable?

Is the mod duo expecting serial communication with 5 volts signal voltage? Will it work with a 3.3V mcu?

Thankful for any answer! If I have totally misunderstood something, please correct me.

I should have mentioned before, the arduino shield hardware project is open and it’s available here: https://github.com/moddevices/cc-arduino-shield

The project requires KiCad software but I’ve generated a PDF file to make it easy: https://github.com/moddevices/cc-arduino-shield/blob/master/hw-design/board/control-chain-arduino-shield.pdf



That’s fine.

Yes. Control Chain uses RS-485 standard, it’s expecting to receive differential signals.

As stated before it is expecting differential signals and the common mode input voltage range is -7V to +12V.

I’d like to remember that you have the option to connect the Arduino into the MOD using the USB cable, but you will need to make those tweaks I’ve mentioned before. That way it wouldn’t require any kind of hardware task. However, if you’re a hardware enthusiastic person, have fun.

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Thanks for the clarification.