diff --git a/configs/config_default.py b/configs/config_default.py
index 49e24ecf21e05b67d55dbc77de65e46ae3c216aa..a553d196350b512f659b49fca3fa7aaaaa575bbd 100644
--- a/configs/config_default.py
+++ b/configs/config_default.py
@@ -49,6 +49,13 @@ HARDWARE_CONFIG = {
             }
     }
 
+'''
+    Dictionnary containing the configuration of the hardware system. THis is where the five modules are declared and assembled together
+    'ctl' contains informationb related to controller unit with the following keys:
+         'model': 'raspberry_pi' only implemented so far
+         'id': ID of thje instrument '0001' by default
+'''
+
 # SET THE LOGGING LEVELS, MQTT BROKERS AND MQTT OPTIONS ACCORDING TO YOUR NEEDS
 # Execution logging configuration
 EXEC_LOGGING_CONFIG = {