How to use BACnet MSTP with Arduino UNO R4

1/*
2 * BACnetLight - Basic Device Example for Arduino UNO R4
3 * 
4 * Simplest BACnet MS/TP device: one Analog Value input and one binary output
5 * Hardware: Arduino UNO R4 + Zihatec RS485 Shield
6 */
7
8
9#include <BACnetLight.h>
10
11// --- definitions ---
12#define RS485_DE   -1   // no DE pin needed - we use the auto transmit function of the shield 
13#define MSTP_MAC   1    // Our MSTP address (0-127)
14#define MSTP_BAUD  38400
15
16
17BACnetMSTP bacnet;
18
19void setup() {
20    Serial.begin(115200);
21    delay(1000);
22    
23    // Set device metadata
24    bacnet.setDeviceInfo("Vendor", 0, "Model", "1.0.0", "1.0.0");
25    
26    Serial1.begin(MSTP_BAUD, SERIAL_8N1);
27    if (!bacnet.beginMSTP(3000, "MSTP-Arduino", Serial1, RS485_DE, MSTP_MAC, MSTP_BAUD)) {
28         Serial.println("ERROR: MSTP init failed!");
29         while (1) delay(1000);
30    }
31    
32    // Analog Input (read-only sensors) 
33    bacnet.addAnalogValue(0, "Temperature", 22.5, BACNET_UNITS_DEGREES_CELSIUS);
34
35    // Binary Output (commandable with priority array)
36    bacnet.addBinaryOutput(0, "Relay", false, "Relay output"); 
37
38    Serial.println("BACnet ready!");
39}
40
41void loop() {
42    bacnet.loop();
43
44    static unsigned long last = 0;
45    if (millis() - last >= 5000) {
46        last = millis();
47
48        // generate random temperature value for fake temp sensor
49        float temp = 20.0 + random(0, 50) / 10.0;
50        bacnet.setValue(BACNET_OBJ_ANALOG_VALUE, 0, temp);
51        Serial.print("Temp: "); Serial.print(temp); Serial.println("°C");
52
53        // control led (binary output)
54        int relay = bacnet.getValue(BACNET_OBJ_BINARY_OUTPUT, 0); 
55        if (relay) {
56            Serial.println("Relay: ON");
57        } else {
58            Serial.println("Relay: OFF");
59        }
60        
61
62    }
63}