[ADD] low-pass tested and work. high-pass added, but not tested

filter_signal/config/filter.yaml

 /**/filter_signal:
   ros__parameters:
-    lowpass_cuttoff_frequency: 5.0
+    lowpass_cuttoff_frequency: 20.0
     signal_topic: sample_wave
     use_sim_time: false

filter_signal/filter_signal/filters.py

@@ -21,3 +21,28 @@ class LowPassFilter():
         filtered_signal = current_signal*(self.sample_time/(self.tau + self.sample_time)) + self.past_filtered_signal*(self.tau/(self.tau + self.sample_time))
         self.past_filtered_signal = filtered_signal
         return filtered_signal  
+    
+class HighPassFilter():
+    def __init__(self, cuttoff_frequency, sample_time):
+        """
+            Implements a first-order low-pass filter.
+            y_k = alpha*(y_{k-1} + x_k - x_{k-1})
+            where:
+            delta_t = sample_time
+            tau = 1/(2*pi*cuttoff_frequency)
+            alpha = tau/(tau + delta_t)
+
+            according to: https://en.wikipedia.org/wiki/High-pass_filter
+        """
+        self.cuttoff_frequency = cuttoff_frequency
+        self.sample_time = sample_time
+        self.tau = 1/(2*np.pi*self.cuttoff_frequency)
+        self.alpha = self.tau/(self.tau + self.sample_time)
+        self.past_filtered_signal = 0.0
+        self.past_signal = 0.0
+
+    def filter(self, current_signal):
+        filtered_signal = self.alpha*(self.past_filtered_signal + current_signal - self.past_signal)
+        self.past_signal = current_signal
+        self.past_filtered_signal = filtered_signal
+        return filtered_signal  
\ No newline at end of file

sample_signal/config/sample_signal.yaml

 /**/sample_signal:
   ros__parameters:
-    publisher_frequency:              50.0                     # Hz
+    publisher_frequency:              200.0                     # Hz
 
     base_signal:                      false
     base_signal_initial_value:        0.0
@@ -11,7 +11,7 @@
     # To satisfy Shannon-Nyquist sampling theorem -> 2*signal_frequency < publisher_frequency.        
     sine_wave:                        true
     sine_wave_components:             [ 2.0,  20.0, 0.0,       # Frequency, amplitude, phase shift(radians) pairs
-                                        10.0, 10.0, 1.57,      # Add as much as needed
+                                        80.0, 10.0, 1.57,      # Add as much as needed
                                         #5.0,  3.0, 3.14 
                                       ]