Martin Simpson
/
Nucleo_SFR05_SFR04
Program with explinations for ease of use of these Ultra-Sonic sensors to give mm resolution
main.cpp
- Committer:
- martinsimpson
- Date:
- 2016-10-17
- Revision:
- 0:2b4e5d360246
- Child:
- 1:221a6fd3d62f
File content as of revision 0:2b4e5d360246:
/* Simple Program to use SFR05 or SFR04 in Single Pin Mode Divide by 5.8 to give mm resolution from microseconds read of Echo pulse Version 1.0a M.Simpson 17/10/2016 */ #include "mbed.h" DigitalInOut TriggerEcho(D8); //Instance of the DigitalInOut class called 'TriggerEcho' Timer pulse; //Instance of the Timer class called 'pulse' float GetDistance(); //Function Prototype int main() { float Distance; //Assign a local variable for the main function pulse.start(); //Start the instance of the class timer while(true) //Continuous loop always true { Distance=GetDistance(); //Get the value returned from the function GetDistance() printf("Distance %.0fmm\n\r",Distance); //Send the value to the serial port for monitoring purposes wait_ms(250); //Wait for 250ms } } float GetDistance(){ //Function Name to be called int EchoPulseWidth=0,EchoStart=0,EchoEnd=0; //Assign and set to zero the local variables for this function TriggerEcho.output(); //Make the DigitalInOut an Output to drive a signal TriggerEcho.write(1); //Signal goes High i.e. 3V3 wait_us(100); //Wait 100us to give a pulse width TriggerEcho.write(0); //Signal goes Low i.e. 0V TriggerEcho.input(); //Make the DigitalInOut an INPUT to accept a signal pulse.reset(); //Rest the instance of the Timer Class while(TriggerEcho.read()==0&&EchoStart<25000){ //wait for Echo to go high EchoStart=pulse.read_us(); //AND with timeout to prevent blocking! } while(TriggerEcho.read()==1&&(EchoEnd-EchoStart<25000)){ //wait for echo to return low EchoEnd=pulse.read_us(); //or'd with timeout to prevent blocking! } EchoPulseWidth=EchoEnd-EchoStart; //time period in us return (float)EchoPulseWidth/5.8f; //calculate distance in mm and reurn the value as a float }