Universal Signal Isolator shield for Arduino DUE & MEGA

A few years back I designed a little Arduino shield who’s main function was to provide electrical isolation between an Arduino and a DAC (specifically a TPA Buffalo III).

The years have passed and my needs have changed with the introduction of the dam1021 DAC and its serial interface. My first though was to design a new shield specific to the dam but then I said “why not design a universal isolator shield?”. It would provide electrical isolation for both I2C as well as serial signalling.

Thus was born the Universal Signal Isolator shield for Arduino DUE & MEGA:


OK, it does look a lot more complicated than my first shield but remember, you only need to solder in the parts that your DAC actually needs.

So, what does this thing do?

1) Electrical isolation of I2C signals, complete with support of 8 isolated inputs or outputs (via an MCP23008 IC). Three of the MCP’s pins are high current outputs (up to 100mA).

2) Electrical isolation of up to 2 serial ports (implemented with an Si8642).

3) Electrical isolation of the second I2C interface of the DUE (implemented with an ADUM1250).

4) Powered either by 5VDC, 8-15VDC (non-regulated) or 7-12VAC (includes support for on-board rectification and filtering).

5) Support of a 5VDC power relay (up to 100mA).

6) Header for connecting a Nextion display.

7) On-board EEPROM memory (24LC256).

8) And of course full compatibility with the previous shield (same pinouts for the encoders, IR, TFT, etc.).

I will release the Eagle files once I have confirmed that the shield works as expected (I’m waiting for the first (and hopefully last) batch of PCBs).



18 thoughts on “Universal Signal Isolator shield for Arduino DUE & MEGA

    • Yes, I believe there is.. 🙂
      (to be exact, there will be once I receive the PCBs and make sure that they are OK)

    • Hi Christian,
      I’m not really making these to sell them, but since I always order way more that I need there are always PCBs left, so I’ll be happy to send you one at cost.

      • Great!

        Have you tested my Xmodem-Arduino-Code? I´ve made some little changes (filter select) and bugfixes. With 0.99 the rs232 connection is very stable….

        Christian 🙂

  1. Hey Dimdim. How are things going? Is your new shield in working order and are there any PCBs left?



    • Hello Fabian,

      Everything is fine here, the shield is in good working order, but I am out of PCBs. However, since I have received many requests for PCBs, I am expecting a new batch pretty soon. I’ll keep you posted. 🙂

    • I don’t think there would be much of a point to a group buy, since I’m already almost giving the boards away (I’m not making any money from them).

      A GB would hint that this is a commercial product, which it isn’t.

      I am out of boards atm but I am waiting on a new batch. I’ll let you know when they get here. 🙂

  2. I would also be interested in getting one of these boards if you had any left 🙂 It seems that Arduino due’s are discontinued, so if I understood correctly this board also works with MEGA. Is there any adjustments that need to be done to code or hardware if I want to control Soekris DAM. I’ve had a board laying around for ages and I think this would be the time to finally start the project. I already have all the SALAS boards and diyinHk usb to i2s boards. I would just need the shield, screen and perhaps the S/PDIF & USB Board as well.

    • AFAIK the DUE is not discontinued, it is very much alive. Discontinuing it wouldn’t make sense without first announcing a successor..

      The board is mostly compatible with the MEGA (except for the second isolated I2C port) but my code will be very very very slow on a MEGA. The code is very graphics intensive, and the MEGA’s 8bit processor is just not designed for that.

      If I were you for this specific application I’d get a DUE. I myself have 2 or 3 MEGAs collecting dust in drawers.

      And do get started on the Soekris. It is one hell of a DAC.

      • Oh yeah, I was looking at the arduino european page that didn’t have all the boards. Due seems to be just out of the stock on the arduino US page, but I can order mine from Mouser if I want to. Thanks for the info 🙂 Do you happen to have any leftover boards of this isolator or the Universal one? I would be very interested in dam1021 S/PDIF & USB Board as well, since it makes things a lot easier and cleaner 🙂

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