How can I read and display the data from my refrigeration serial port?

Hi, I'm new to the forum, but have some minimal experience with microcontrollers, mainly making lights blink, etc. I live onboard my 39' sailboat the Sea Bear, which I am outfitting to circumnavigate. I am currently enrolled in a marine systems certification course, focusing on marine electrical. While re-designing the Sea Bear's electrical system, I realized that my 12V refrigerator ( going to be my largest continuous amp draw, and any improvements I make to the system will pay off with increased efficiency and a smaller electrical footprint in the boat. I'm an empirical kind of guy, so I would like to keep a digital log, tracking and displaying temperature, voltage and amps, both instantaneously and over time. Displaying averages over the past 1 hour and 24 hours would also be nice. That way as I make changes to the insulation, seals, external compressor fan, etc. I can have a good idea of how the changes effect my total amp draw.

While considering what kind of sensors I would need to do that, I started digging in to the refrigerators tech manual and discovered that the compressor controller, a FDC1 electronic driver ( has what appears to be a serial controller. From the data sheet:

The electronic control unit FDC1 is supplied with the exclusive Serial Port Interface (SPI), featuring a RJ11 telephone type connector. This port allows the electronic driver to be connected to a computer for programming purposes using the FDC programming package (hardware and software) provided by ACC under request. Optionally, the SPI can be configured to:

  1. Install a LED to display the intervention of any alarm.

  2. Set up either the compressor speed or the battery protection level, through physical connections between IN1, IN2 and COM.

  3. Connect the electronic driver as slave to an Electronic Integral Manager (EIM) of the appliance with serial communication capabilities (Rx, Tx and COM), to allow working with variable speed. SPI provides a 5 V output, limited to 25mA, to power up the EIM.

Additionally, I found a datasheet describing the communications protocol: ( I'm most interested in reading the output, and not programing the FDC1 electronic driver.

So my question is, is it possible to connect an Arduino to this serial port and read the data being sent? If it is possible, what would the best model of Arduino to use, considering the data-logging and display parts? Thank you for taking the time to consider my project, I look forward to reading and learning from any replies.

Shawn s/v Sea Bear

I read the documentation PDF you linked to. Did you see something that led you to believe you could monitor the status of the refrigerator?


@Paul_KD7HB, are you referring to the protocol document?

Looks like this is a normal TTL serial interface.

@seabearshawn You basically can use any 5V Arduino; easiest option might be one with an additional serial port (Mega, Leonardo, Micro) although using SoftwareSerial (or one of its alternatives) will also work at 1200 baud.

You can also log directly to a PC using a USB-to-TTL adapter and a suitable application.

Thank you for your replies! @Paul_KD7HB I was thinking it might be possible because of this line above the table in the protocol document:

OUTPUT Every 0’5 s, one of these 6-byte sequences is sent:

(rest of table)


I suggest you try some of the examples in Serial Input Basics (probably start with the 2nd one) and see can you capture any useful information.

You will probably need to experiment to see what baud rate is used.

I suggest you do the experiments with a Mega because it has additional HardwareSerial ports so you can leave Serial free for communication with your PC.


Thanks for the direction. I have ordered a Mega, it will be here Tuesday.


Hello there seabearshawn!

You referenced the copy of the Cubigel protocol on my web pages, but somehow missed the fact that I've already written an Arduino Library for communications with the FDC based on that protocol. I use it to monitor and optimize energy consumption for my fridge and freezer (both use Cubigel compressors).

The library along with example program and wiki pages/documentation can be found at GitHub Cubigel Arduino Library

I'm postponing my circumnavigation a bit, as the Caribbean is nice and once through the Panama there's really no going back and one needs to continue through the Pacific to New Zealand or Oz.

hello i want reprogramm my cubigel card because i change tne compressor it is possible with arduino think you very much