Parsing a serial stream too slowly

[M.Pekala]

Hello, I am having some trouble with a serial stream on a project I am
working on. I have an external board that is attached to a set of
sensors. The board polls the sensors, filters them, formats the
values, and sends the formatted values over a serial bus. The serial
stream comes out like $A1234$$B-10$$C987$,  where "$A.*$" is a sensor
value, "$B.*$" is a sensor value, "$C.*$" is a sensor value, ect...

When one sensor is running my python script grabs the data just fine,
removes the formatting, and throws it into a text control box. However
when 3 or more sensors are running, I get output like the following:

Sensor 1: 373
Sensor 2: 112$$M-160$G373
Sensor 3: 763$$A892$

I am fairly certain this means that my code is running too slow to
catch all the '$' markers. Below is the snippet of code I believe is
the cause of this problem...

def OnSerialRead(self, event):
	text = event.data
	self.sensorabuffer = self.sensorabuffer + text
	self.sensorbbuffer = self.sensorbbuffer + text
	self.sensorcbuffer = self.sensorcbuffer + text

	if sensoraenable:
		sensorresult = re.search(r'\$A.*\$.*', self.sensorabuffer )
			if sensorresult:
				s = sensorresult.group(0)
				s = s[2:-1]
				if self.sensor_enable_chkbox.GetValue():
					self.SensorAValue = s
				self.sensorabuffer = ''

	if sensorbenable:
		sensorresult = re.search(r'\$A.*\$.*', self.sensorbenable)
			if sensorresult:
				s = sensorresult.group(0)
				s = s[2:-1]
				if self.sensor_enable_chkbox.GetValue():
					self.SensorBValue = s
				self.sensorbenable= ''

	if sensorcenable:
		sensorresult = re.search(r'\$A.*\$.*', self.sensorcenable)
			if sensorresult:
				s = sensorresult.group(0)
				s = s[2:-1]
				if self.sensor_enable_chkbox.GetValue():
					self.SensorCValue = s
				self.sensorcenable= ''

        self.DisplaySensorReadings()

I think that regex is too slow for this operation, but I'm uncertain
of another method in python that could be faster. A little help would
be appreciated.