diff --git a/sonoff/support.ino b/sonoff/support.ino
index 10bbd2194..3baa88f2d 100644
--- a/sonoff/support.ino
+++ b/sonoff/support.ino
@@ -1264,6 +1264,7 @@ void SetNextTimeInterval(unsigned long& timer, const unsigned long step)
 #ifdef USE_I2C
 const uint8_t I2C_RETRY_COUNTER = 3;
 
+uint32_t i2c_active[4] = { 0 };
 uint32_t i2c_buffer = 0;
 
 bool I2cValidRead(uint8_t addr, uint8_t reg, uint8_t size)
@@ -1457,12 +1458,35 @@ void I2cScan(char *devs, unsigned int devs_len)
   }
 }
 
+void I2cSetActive(uint32_t addr, uint32_t count = 1)
+{
+  addr &= 0x7F;
+  count &= 0x7F;
+  while (count-- && (addr < 128)) {
+    i2c_active[addr / 32] |= (1 << (addr % 32));
+    addr++;
+  }
+//  AddLog_P2(LOG_LEVEL_DEBUG, PSTR("I2C: Active %08X,%08X,%08X,%08X"), i2c_active[0], i2c_active[1], i2c_active[2], i2c_active[3]);
+}
+
+bool I2cActive(uint32_t addr)
+{
+  addr &= 0x7F;
+  if (i2c_active[addr / 32] & (1 << (addr % 32))) {
+    return true;
+  }
+  return false;
+}
+
 bool I2cDevice(uint8_t addr)
 {
+  if (I2cActive(addr)) {
+    return false;       // If already active report as not present;
+  }
   for (uint8_t address = 1; address <= 127; address++) {
     Wire.beginTransmission(address);
     if (!Wire.endTransmission() && (address == addr)) {
-      return true;
+      return true;      // Report as present;
     }
   }
   return false;