[Issue #2] - adding code to verify a display is connected before attempting to use it

main.go

@@ -308,17 +308,30 @@ func main() {
 		panicErr("I2C configuration", err)
 	}
 
-	// Initialize OLED (shares the same I2C bus at 0x3C)
-	oled := ssd1306.NewI2C(i2c)
-	oled.Configure(ssd1306.Config{
-		Address: 0x3C, // Check 0x3D if 0x3C doesn't respond
+	// Instantiate nil oled variable
+	var oled *ssd1306.Device
+	// White color for display
+	white := color.RGBA{R: 255, G: 255, B: 255, A: 255}
+
+	// Probe address 0x3C with a zero-byte or 1-byte read
+	var dummy [1]byte
+	if err := i2c.ReadRegister(0x3C, 0x00, dummy[:]); err == nil {
+	    println("SSD1306 detected at 0x3C")
+	    dev := ssd1306.NewI2C(i2c)
+	    dev.Configure(ssd1306.Config{
+	        Address: 0x3C,
 	        Width:   128,
 	        Height:  64,
 	    })
+	    oled = dev
+
+			// Run some initial clearing and add booting text to the screen
 			oled.ClearBuffer()
-	white := color.RGBA{R: 255, G: 255, B: 255, A: 255}
 			tinyfont.WriteLine(oled, &proggy.TinySZ8pt7b, 0, 16, "Booting...", white)
 			oled.Display()
+	} else {
+	    println("SSD1306 not found — running headless")
+	}
 
 	bme, err := NewBME280(i2c, BME280Addr)
 	if err != nil {
@@ -364,6 +377,7 @@ func main() {
 			}
 
 			// Render to OLED
+			if oled != nil {
 		    oled.ClearBuffer()
 		    tinyfont.WriteLine(oled, &proggy.TinySZ8pt7b, 0, 14, fmt.Sprintf("Node: %s", NodeName), white)
 		    tinyfont.WriteLine(oled, &proggy.TinySZ8pt7b, 0, 30, fmt.Sprintf("Temp: %.1f C", t), white)
@@ -371,6 +385,7 @@ func main() {
 		    tinyfont.WriteLine(oled, &proggy.TinySZ8pt7b, 0, 60, fmt.Sprintf("Pres: %.1f hPa", p), white)
 		    oled.Display()
 			}
+		}
 
 		time.Sleep(UpdateInterval)
 	}