diff --git a/voltage-current-monitor-usb.ino b/voltage-current-monitor-usb.ino
index cfb3f80..3e72f8b 100644
--- a/voltage-current-monitor-usb.ino
+++ b/voltage-current-monitor-usb.ino
@@ -13,6 +13,10 @@
 #define OLED_RESET -1
 #define SCREEN_ADDRESS 0x3C
 
+float voltage = 0;
+float current = 0;
+float wattage = 0;
+
 Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
 void setup() {
   Serial.begin(115200);