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michpromichpro
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interactive OpenTherm shield testing program
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‎software/shield_test/shield_test.ino‎

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/**
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* \file shield_test.ino
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* \brief This Arduino program is a diagnostic tool designed to test and validate the electrical and communication integrity
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* between a boiler and thermostat circuits on the OpenTherm shield.
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* It guides the user through a step-by-step verification process via serial prompts, checking voltages, currents, and LED statuses.
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* The setup() function initializes hardware pins and performs sequential tests with user measurements and confirmation,
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* while the loop() continuously validates bidirectional signal communication between boiler and thermostat if all initial tests pass.
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* The program provides real-time feedback via serial output, indicating "TEST PASSED" or "TEST FAIL" based on user input and hardware responses.
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*
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* \copyright SPDX-FileCopyrightText: Copyright 2025 Michal Protasowicki
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*
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* \license SPDX-License-Identifier: MIT
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*
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*/
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#if !defined(ARDUINO_ARCH_AVR)
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#error "Use only with Arduino AVR family!!!"
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#endif
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#include <Arduino.h>
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// Arduino UNO
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const int MASTER_IN {2};
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const int SLAVE_IN {3};
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const int MASTER_OUT {4};
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const int SLAVE_OUT {5};
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const int DELAY_DEV_MS {40};
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const int DELAY_LOOP_MS {2000};
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const char CONFIRM_M_STR[] PROGMEM {"If the measurement is correct, send 'y' to proceed to the next step."};
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const char CONFIRM_P_STR[] PROGMEM {"If so, press 'y' to proceed to the next step."};
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const char MASTER_ACT_STR[] PROGMEM {"The 'MASTER-OUT' line has been activated."};
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const char RXT_NLIT_STR[] PROGMEM {"The RxT LED should not be lit during the measurement."};
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const char MEAS_B1_B2_STR[] PROGMEM {"Measure the voltage between test points B1 and B2."};
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const char FAILED_STR[] PROGMEM {"Failed"};
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const char OK_STR[] PROGMEM {"OK"};
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const char LINE_STR[] PROGMEM {"----------------------------------------------------------------------------------"};
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const char STARS_STR[] PROGMEM {"*****************"};
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bool next {false};
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bool waitForYes(void)
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{
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bool result {true};
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bool exit {false};
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char chr {0};
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while (!exit)
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{
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while (!SERIAL_PORT_MONITOR.available()) {};
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while (SERIAL_PORT_MONITOR.available() > 0)
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{
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chr = SERIAL_PORT_MONITOR.read();
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switch (chr)
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{
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case 'n':
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case 'N':
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exit = true;
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result = false;
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break;
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case 'y':
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case 'Y':
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exit = true;
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break;
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default:
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break;
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}
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}
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}
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return result;
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}
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void setup()
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{
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SERIAL_PORT_MONITOR.begin(115200);
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while (!SERIAL_PORT_MONITOR) {}
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pinMode(MASTER_IN, INPUT);
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pinMode(SLAVE_IN, INPUT);
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pinMode(MASTER_OUT, OUTPUT); // low output = high current, high output = low current
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pinMode(SLAVE_OUT, OUTPUT); // low output = high voltage, high output = low voltage
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digitalWrite(MASTER_IN, HIGH);
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digitalWrite(MASTER_OUT, HIGH);
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digitalWrite(SLAVE_IN, HIGH);
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digitalWrite(SLAVE_OUT, LOW);
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SERIAL_PORT_MONITOR.println(F("Disconnect the 'THERM' and 'BOILER' terminals if they are connected to each other."));
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SERIAL_PORT_MONITOR.println(F("The 'PWR' and 'RxT' LEDs should light up, and the 'RxB' LED should be off."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_P_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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if (next)
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{
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SERIAL_PORT_MONITOR.println(F("Measure the voltage between the +24V test point and GND."));
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SERIAL_PORT_MONITOR.println(F("It should be between 23.5V and 24.5V."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_M_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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}
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if (next)
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{
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SERIAL_PORT_MONITOR.println(F("Measure the voltage between the T+ test point and GND."));
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SERIAL_PORT_MONITOR.println(F("It should be approximately 24V."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_M_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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}
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if (next)
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{
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SERIAL_PORT_MONITOR.println(F("Measure the current flowing between the T+ test point and GND."));
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SERIAL_PORT_MONITOR.println(F("It should be between 5mA and 9mA."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)RXT_NLIT_STR);
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_M_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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}
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if (next)
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{
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digitalWrite(MASTER_OUT, LOW);
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)MASTER_ACT_STR);
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SERIAL_PORT_MONITOR.println(F("Measure the current flowing between the T+ test point and GND again."));
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SERIAL_PORT_MONITOR.println(F("It should be between 17mA and 23mA."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)RXT_NLIT_STR);
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_M_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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digitalWrite(MASTER_OUT, HIGH);
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}
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if (next)
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{
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SERIAL_PORT_MONITOR.println(F("Connect the BOILER and THERM terminals with two wires [polarity is irrelevant]."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)MEAS_B1_B2_STR);
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SERIAL_PORT_MONITOR.println(F("It should be between 15V and 18V."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_M_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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}
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if (next)
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{
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digitalWrite(MASTER_OUT, LOW);
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)MASTER_ACT_STR);
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SERIAL_PORT_MONITOR.println(F("The 'RxB' LED should light up."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_P_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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digitalWrite(MASTER_OUT, HIGH);
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}
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if (next)
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{
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digitalWrite(SLAVE_OUT, HIGH);
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SERIAL_PORT_MONITOR.println(F("The 'SLAVE-OUT' line has been activated."));
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SERIAL_PORT_MONITOR.println(F("The RxT LED should stop lighting up."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)MEAS_B1_B2_STR);
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SERIAL_PORT_MONITOR.println(F("It should be between 5V and 7V."));
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)CONFIRM_M_STR);
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next = waitForYes();
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)LINE_STR);
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digitalWrite(SLAVE_OUT, LOW);
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}
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)STARS_STR);
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if (next)
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{
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SERIAL_PORT_MONITOR.println(F("* TEST PASSED *"));
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} else
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{
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SERIAL_PORT_MONITOR.println(F("* TEST FAIL !!! *"));
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}
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SERIAL_PORT_MONITOR.println((const __FlashStringHelper *)STARS_STR);
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}
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void loop()
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{
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if (next)
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{
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Serial.print(F("Boiler inbound, thermostat outbound ... "));
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digitalWrite(MASTER_OUT, HIGH);
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digitalWrite(SLAVE_OUT, HIGH);
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delay(DELAY_DEV_MS);
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if ((LOW == digitalRead(MASTER_IN)) && (LOW == digitalRead(SLAVE_IN)))
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{
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digitalWrite(MASTER_OUT, LOW); // thermostat out low -> boiler in high
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delay(DELAY_DEV_MS);
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if ((LOW == digitalRead(MASTER_IN)) && (HIGH == digitalRead(SLAVE_IN)))
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{
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Serial.println((const __FlashStringHelper *)OK_STR);
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} else
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{
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Serial.println((const __FlashStringHelper *)FAILED_STR);
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Serial.println(F("Boiler is not registering signal or thermostat is not sending properly"));
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}
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} else
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{
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Serial.println((const __FlashStringHelper *)FAILED_STR);
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Serial.println(F("Boiler is high even if no signal is being sent"));
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}
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Serial.print(F("Boiler outbound, thermostat inbound ... "));
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digitalWrite(MASTER_OUT, HIGH);
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digitalWrite(SLAVE_OUT, HIGH);
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delay(DELAY_DEV_MS);
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if ((LOW == digitalRead(MASTER_IN)) && (LOW == digitalRead(SLAVE_IN)))
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{
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digitalWrite(SLAVE_OUT, LOW); // boiler out low -> thermostat in high
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delay(DELAY_DEV_MS);
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if ((HIGH == digitalRead(MASTER_IN)) && (LOW == digitalRead(SLAVE_IN)))
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{
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Serial.println((const __FlashStringHelper *)OK_STR);
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} else
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{
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Serial.println((const __FlashStringHelper *)FAILED_STR);
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Serial.println(F("Thermostat is not registering signal or boiler is not sending properly"));
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}
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} else
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{
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Serial.println((const __FlashStringHelper *)FAILED_STR);
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Serial.println(F("Thermostat is high even if no signal is being sent"));
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}
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delay(DELAY_LOOP_MS);
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}
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}

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