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Discover how the Arduino Opta Pro can be leveraged beyond its industrial roots for smart home and DIY automation. In my article, I share hands‑on insights, practical code examples, and hardware extensions like FRAM integration to enable reliable pulse counting and persistent data storage. Whether you’re curious about Opta’s STM32 Cortex‑M4F power, its DIN‑rail form factor, or its seamless link with Arduino Cloud, this write‑up offers a clear, tested path to getting the most out of this versatile controller.

I took advantage of Black Friday to purchase an Opta Pro, a compact industrial controller designed and manufactured by Arduino. My goal was to evaluate the product and see whether it could fit into my home automation systems.

The mechanical format is very convenient: DIN‑rail mounting makes installation straightforward, and the screw terminals are easy to access. Front‑panel LEDs and a USER button provide quick ways to test functionality.

For my initial experiments, I connected the Opta Pro via Ethernet and powered it with a small 12 V supply. Although the Opta supports Grafcet programming, I preferred to develop my own applications using the Arduino IDE and integrate them with Arduino Cloud for remote access via my iPhone.

First Challenges

At the beginning, I ran into a few issues. The Opta Pro is powered by a STM32 ARM Cortex‑M4F running at 168 MHz, which is quite different from the ESP32 I was more familiar with. This meant I had to be careful when selecting libraries.

One of my first problems was the use of while(!Serial) to validate the presence of a serial connection. I noticed that if the USB‑C port was not connected, and the system was only powered externally, the program would hang at that instruction. I quickly worked around this in setup() with the following code:
Serial.begin(115200);                                                             // Initialize serial and wait for port to open
unsigned long start = millis();
while (!Serial && (millis() - start < 2000)) {}
if (Serial) {
    serialActive = true;
    Serial.println("\nSerial port connected to USB");
}

Another issue was my usual NTP time routines, which no longer worked as expected. I rewrote them, and now the system maintains a date_Time variable updated every second. This value is displayed on my iPhone, ensuring I can always confirm the system is alive (the RUN LED also stays lit).

Adding FRAM for Persistent Storage

One of my future projects involves counting energy pulses from three meters (1 pulse per kWh consumed). I quickly realized that the Opta lacked non‑volatile memory beyond Flash, which is not ideal for logging counters.

To solve this, I added an FRAM module via the Aux expansion connector, which conveniently exposes SDA, SCL, +3.3 V, and GND from one of the STM32’s I²C ports. I used an Adafruit library to handle this component.

Test Program Features

To validate everything, I wrote a test program (included in the appendix) with the following features:

  • Relay control: Each relay can be switched ON/OFF either via a local input (+12 V active) or remotely through the iPhone app. The input state and corresponding Status LED are displayed.
  • USER button test: Pressing the front‑panel USER button activates relay 4.
  • Analog input: Reads a 10‑bit analog value from IN5.
  • Pulse counters: IN6, IN7, and IN8 each increment a separate 32‑bit counter. Pulses are filtered at 50 ms and handled via interrupts. The Status LED flashes for 100 ms on each pulse. Counter values are permanently stored in FRAM. To avoid miscounts, the interrupt for the active channel is temporarily suspended during processing.
  • Cloud monitoring: The loop continuously checks the Arduino Cloud connection, and the system can even be rebooted remotely if needed. Startup and synchronization times are displayed on the dashboard.

Conclusion:

My application has now been running continuously for about two weeks without a single crash. A watchdog monitors the Arduino Cloud connection with a 5‑minute timeout, but the system has never rebooted. Using Ethernet, the connection reliability is excellent. I did not choose the WiFi option, but I suspect Ethernet is the more robust solution.

If you have any questions, feel free to contact me at yb.electronique@orange.fr. I now have a solid grasp of the Opta Pro and will be happy to help if needed!