description updated

Author: abtom87

README.md

@@ -29,6 +29,10 @@ LCD Display is controlled via I2C bus. In this project i have used GPS module to
 * ST-Link Support
 * Salae Logicanalyzer GUI.
 * Operating System- Ubuntu Linux
+
+## Source code features
+* FreeRTOS port for CortexM4
+* Standard Peripheral Libraries (StdPeriph_Driver)
 
 ## Working principle - Distance
 The HC-04 module has Trigger and Echo pin. 
@@ -42,10 +46,11 @@ Timer 2 (TIM2-CH3) is configured to send the trigger signal with a specific duty
 Depending on the distance a pulse is generated by echo Pin.The Echo pin is connected to input capture Pin (Timer1-CH1).
 The Pulsewidth of the received pulse in milliseconds is used to determine the distance.
 
-For more details refer this site https://www.mouser.com/ds/2/813/HCSR04-1022824.pdf
+For more details refer this PDF. https://www.mouser.com/ds/2/813/HCSR04-1022824.pdf
 
 
 Sound travels at approx. 343 meters/second. Distance in centimeters is hence, (pulsewidth(ms)*34300(cm/s))/2;
+
 Distance in cm = (PW/1000)seconds * (17150)(cm/seconds)
 
 <img src="./Images/Image1_Trig_echo.png" alt="img" width="600"/>