Merge pull request #44 from sparkfun/bboyho-FPS_Blink-patch-1

Update FPS_Blink.ino

Author: bboyho

FPS_GT511C3/Examples/FPS_Blink/FPS_Blink.ino

@@ -5,28 +5,73 @@
 	basically, Feel free to hack away at it, but just give me credit for my work =)
 	TLDR; Wil Wheaton's Law
 
-	This simple sketch turns the LED on and off similar to the Arduino blink sketch.
+        Description: This simple sketch turns the LED on and off similar to the Arduino blink sketch.
 	It is used to show that communications are working.
+	
+	This code should work with the any model of ADH-Tech's FPS as long as
+	you are within the minimum logic level threshold for the FPS serial UART.
+	This code has been tested with these models:
+ 
+              GT-511C3  [ https://www.sparkfun.com/products/11792 ]
+              GT-511C1R [ https://www.sparkfun.com/products/13007 ]
+	
 */
 
 #include "FPS_GT511C3.h"
 #include "SoftwareSerial.h"
 
-// Hardware setup - FPS connected to:
-//	  digital pin 4(arduino rx, fps tx)
-//	  digital pin 5(arduino tx - 560ohm resistor fps tx - 1000ohm resistor - ground)
-//		this brings the 5v tx line down to about 3.2v so we dont fry our fps
+/*-------------------- HARDWARE HOOKUP with 5V Arduino --------------------
+1.) Dedicated Bi-Directional Logic Level Converter (LLC)
 
-FPS_GT511C3 fps(4, 5);
+It is recommended to use a dedicated bi-direcitonal LLC
+[ https://www.sparkfun.com/products/12009 ] for a reliable connection if you
+are using a 5V Arduino microcontroller:
+
+   Fingerprint Scanner (Pin #) <-> Logic Level Converter <-> 5V Arduino w/ Atmega328P
+     UART_TX (3.3V TTL)(Pin 1) <->     LV1 <-> HV1       <->  RX (pin 4)
+     UART_RX (3.3V TTL)(Pin 2) <->     LV4 <-> HV4       <->  TX (pin 5)
+           GND         (Pin 3) <->     GND <-> GND       <->     GND
+      Vin (3.3V~6V)    (Pin 4) <->        HV             <->      5V
+                                          LV             <->     3.3V
+					  
+2.) Voltage Division w/ 3x 10kOhm Resistors
+
+Otherwise, you could use 3x 10kOhm resistors [ https://www.sparkfun.com/products/11508 ]
+to divide the voltage from a 5V Arduino down to 3.3V FPS similar to the
+"Uni-Directional" application circuit on our old logic level converter
+[ https://cdn.sparkfun.com/assets/b/0/e/1/0/522637c6757b7f2b228b4568.png ]:
+
+    Voltage Divider         <-> Fingerprint Scanner(Pin #) <-> Voltage Divider <-> 5V Arduino w/ Atmega328P
+                            <-> UART_TX (3.3V TTL) (Pin 1) <->                 <->       RX (pin 4)
+  GND <-> 10kOhm <-> 10kOhm <-> UART_RX (3.3V TTL) (Pin 2) <->      10kOhm     <->       TX (pin 5)
+          GND               <->        GND         (Pin 3) <->       GND       <->        GND
+                            <->    Vin (3.3V~6V)   (Pin 4) <->                 <->        5V
+			    
+Note: You can add the two 10kOhm resistors in series for 20kOhms. =)
+
+--------------------------------------------------------------------------------*/
+
+// set up software serial pins for Arduino's w/ Atmega328P's
+// FPS (TX) is connected to pin 4 (Arduino's Software RX)
+// FPS (RX) is connected through a converter to pin 5 (Arduino's Software TX)
+FPS_GT511C3 fps(4, 5); // (Arduino SS_RX = pin 4, Arduino SS_TX = pin 5)
+
+/*If using another Arduino microcontroller, try commenting out line 57 and
+uncommenting line 66 due to the limitations listed in the
+library's note => https://www.arduino.cc/en/Reference/softwareSerial . Do
+not forget to rewire the connection to the Arduino*/
+
+// FPS (TX) is connected to pin 10 (Arduino's Software RX)
+// FPS (RX) is connected through a converter to pin 11 (Arduino's Software TX)
+//FPS_GT511C3 fps(10, 11); // (Arduino SS_RX = pin 10, Arduino SS_TX = pin 11)
 
 void setup()
 {
-	Serial.begin(9600);
+	Serial.begin(9600); //set up Arduino's hardware serial UART
 	fps.UseSerialDebug = true; // so you can see the messages in the serial debug screen
-	fps.Open();
+	fps.Open(); //send serial command to initialize fps
 }
 
-
 void loop()
 {
 	// FPS Blink LED Test