Adds rx bias calibration

ohmpi/hardware_components/ohmpi_card_3_15.py

@@ -254,6 +254,6 @@ class Rx(RxAbstract):
         """ Gets the voltage VMN in Volts
         """
         self.exec_logger.event(f'{self.board_name}\trx_voltage\tbegin\t{datetime.datetime.utcnow()}')
-        u = AnalogIn(self._ads_voltage, ads.P0, ads.P1).voltage * self._coef_p2 * 1000. - self._bias # TODO:  check if it should be negated
+        u = AnalogIn(self._ads_voltage, ads.P0, ads.P1).voltage * self._coef_p2 * 1000. - self._bias  # TODO:  check if it should be negated
         self.exec_logger.event(f'{self.board_name}\trx_voltage\tend\t{datetime.datetime.utcnow()}')
         return u

ohmpi/hardware_system.py

@@ -319,7 +319,7 @@ class OhmPiHardware:
         plt.show()
 
     def calibrate_rx_bias(self):
-        self.tx._bias = np.mean(self.readings[self.readings[:, 2] == 1, 4]) \
+        self.rx._bias = np.mean(self.readings[self.readings[:, 2] == 1, 4]) \
                       + np.mean(self.readings[self.readings[:, 2] == -1, 4]) / 2.
 
     def vab_square_wave(self, vab, cycle_length, sampling_rate=None, cycles=3, polarity=1, append=False):