diff --git a/I2C_serial.py b/I2C_serial.py
index b49776a5b7e91586ac182a17d4cbdd075b26756a..d2195df0fc0cf76be24ff616689a5a49f9d4ca9a 100644
--- a/I2C_serial.py
+++ b/I2C_serial.py
@@ -19,6 +19,7 @@ class I2C:
 
     def __init__(self, ADDRESS='040'):
         self.I2C_Address = ADDRESS
+        self.BUS_NR = 1 # not used for Laptop but to enable Pi multiple busses.
 
 
 #    def chk_ack(self):
diff --git a/I2C_serial_pi.py b/I2C_serial_pi.py
index d9b98233550ac695493bd17e798cbd1c777f4b26..d928b77db33c00b86e96b3bf84ff1314a6515011 100644
--- a/I2C_serial_pi.py
+++ b/I2C_serial_pi.py
@@ -23,14 +23,13 @@ import sys
 from time import *
 
 DEBUG=False
-BUS_NR = 1
 
 class I2C:
 
     def __init__(self, ADDRESS='040'):
         self.I2C_Address = ADDRESS
-
-        bus = smbus.SMBus(BUS_NR)
+        self.BUS_NR = 1
+        bus = smbus.SMBus(self.BUS_NR)
 
 
     def read_bytes(self, register, bytes_to_read=2):
diff --git a/check_adc_lock.py b/check_adc_lock.py
index 090d44590d21925815fb495731618a68a34a54b2..7e85a592e23d05104fda019d4c9005c4c499cc83 100644
--- a/check_adc_lock.py
+++ b/check_adc_lock.py
@@ -20,9 +20,11 @@ sys.path.insert(0,'.')
 import os
 if os.name =="posix":
     from I2C_serial_pi import *
+
 else:
     from I2C_serial import *
 
+I2CBUSNR=1
 sleep_time=0.05
 WRITE_DATA = True
 READ_BYTE = True
@@ -40,6 +42,7 @@ def Read_byte_ADC(ADC_reg_address, ADC_bytes=0, ADC_NR = 0, ADDRESS=0x20 ):
     # Read Byte from the ADC
     #
     I2C_device = I2C(ADDRESS)
+    I2C_device.bus = I2CBUSNR
     ADC_rw    = 0x01 # 0 for write, 1 for read
     
     stri = "Read ADC from Address {:8x}".format(ADC_reg_address)
diff --git a/set_clk.py b/set_clk.py
index cb1d565c74827e77467a403309459b6206fc5266..dff55970d304dec63ce8df13830a1750f35992ef 100644
--- a/set_clk.py
+++ b/set_clk.py
@@ -23,6 +23,7 @@ if os.name =="posix":
 else:
     from I2C_serial import *
 
+I2CBUSNR=1
 sleep_time=0.05
 PWR_RST = False
 SET_PLL = True
@@ -42,6 +43,7 @@ def Write_byte_PLL(reg_address, wr_data, ADDRESS=0x20):
     # Write Byte to the ADC
     #
     I2C_device = I2C(ADDRESS)
+    I2C_device.bus = I2CBUSNR
     PLL_rw    = 0x00 # 0 for write, 1 for read
     stri = "Write : 0x{0:{fill}2x} to Address : 0x{1:{fill}2x}".format(wr_data, reg_address, fill='0')
     print(stri)
@@ -69,6 +71,7 @@ def Read_byte_PLL(reg_address, nof_bytes=1, ADDRESS=0x20 ):
     # Read Byte from the ADC
     #
     I2C_device = I2C(ADDRESS)
+    I2C_device.bus = I2CBUSNR
     PLL_rw    = 0x01 # 0 for write, 1 for read
 
     I2C_device.write_bytes(0x06, 0x2C)
@@ -105,6 +108,7 @@ def Read_byte_PLL(reg_address, nof_bytes=1, ADDRESS=0x20 ):
 def power(state):
     ADDRESS_IO = 0x20
     I2C_IO_device = I2C(ADDRESS_IO)
+    I2C_device.bus = I2CBUSNR
     I2C_IO_device.write_bytes(0x06, 0x2C)
     I2C_IO_device.write_bytes(0x07, 00)
     if state: