It works!

mission/blackbox/blackbox/blackbox_log_data.py

@@ -30,10 +30,11 @@ def __init__(self,
         self.manage_csv_files()
 
         # Make new .csv file for loging blackbox data ----------
-        with open(self.data_file_location, mode='w', newline='') as csv_file:
+        with open(self.data_file_location, mode="w", newline="") as csv_file:
             writer = csv.writer(csv_file)
             writer.writerow(self.csv_headers)
-
+
+    # Methods for inside use of the class ----------
     def manage_csv_files(self, max_file_age_in_days=1, max_size_kb=3_000):         #adjust the max size before you start deleting old files (1 000 000 kb = 1 000 mb = 1 gb)
         current_time = datetime.now()
         older_than_time = current_time - timedelta(days=max_file_age_in_days)
@@ -75,8 +76,19 @@ def manage_csv_files(self, max_file_age_in_days=1, max_size_kb=3_000):         #
             total_size_kb = sum(os.path.getsize(os.path.join(self.blackbox_data_directory, f)) for f in os.listdir(self.blackbox_data_directory) if f.endswith('.csv')) / 1024
             print(f'Now the total size of .csv files is: {total_size_kb:.2f} KB')
 
+    # Methods for external uses ----------
     def log_data_to_csv_file(self,
-        POWER_SENSE_MODULE_CURRENT = 0.0,
-        POWER_SENSE_MODULE_VOLTAGE = 0.0
+        psm_current = 0.0,
+        psm_voltage = 0.0,
     ):
-        pass
+        # Get current time in hours, minutes, seconds and miliseconds
+        current_time = datetime.now().strftime("%H:%M:%S.%f")[:-3]
+
+        # Write to .csv file
+        with open(self.data_file_location, mode="a", newline="") as csv_file:
+            writer = csv.writer(csv_file)
+            writer.writerow([
+                current_time,
+                psm_current,
+                psm_voltage,
+            ])

mission/blackbox/blackbox/blackbox_node.py

@@ -53,7 +53,6 @@ def __init__(self):
             "/asv/power_sense_module/voltage [Float32] \n"
         )
 
-
     # Callback Methods ----------
     def psm_current_callback(self, msg):
         self.psm_current_data = msg.data
@@ -62,7 +61,10 @@ def psm_voltage_callback(self, msg):
         self.psm_voltage_data = msg.data
 
     def logger(self):
-        pass
+        self.blackbox_log_data.log_data_to_csv_file(
+            psm_current=self.psm_current_data,
+            psm_voltage=self.psm_voltage_data,
+        )