So How does it work

Published December 7, 2015 © GPL3+

PSoC 4: Measuring Distance with HCSR-04 and CY8CKIT-049 4200

Pulse High measurement (proportional to distance) of HCSR-04 (Echo pin) UltraSonic Ranging module using Timer component of PSoC 4

IntermediateProtip6,952

PSoC 4: Measuring Distance with HCSR-04 and CY8CKIT-049 4200

Things used in this project

Hardware components

Cypress PSoC 4 Prototyping Kit

Story

With Arduino, this is no big deal, right ?

Just digitalWrite "high" the trigger pin for a few micro second then pulseIn the echo pin to measure the pulse duration in time, convert that time to distance !

How do you do that in PSoC 4 ?Do some math to get the time and print on the LCD !

So How does it work ?

The Trigger (also the LED pin for a short BLUE flash) named Output Pin of PSoC, which is connected to the Trigger Input of the the Ultrasonic Module, is made HIGH for 10 microsecond on every 500 millisecond to Trigger the Module for sending ultrasonic waves. This is done from the C code, which means this part is dealt by the CPU (ARM M0 in PSoC).

Note that, both Trigger and LED are controlled from software.

Then the Echo Pin of the Module will generate a High Pulse, the width of the pulse depends on the measured distance. To measure this duration, a Hardware Timer component of PSoC is used.

PSoC Creator

Configuring Timer Component

From, HC 04 Ultrasonic Module's datasheet,

Pulse High Duration on Echo (in uS)/58 = 1 cm

Maximum Measurable Length 4 meters = 400 cm will be represented with a 400 x 58 = 23200 uS High Pulse. So, Timer Period (here 65535) must be > 23200.

Check the above image -

Counter mode : Up ( counts from 0 towards 65535 )

Run mode : 1 shot ( once stopped, won't start unless started again )

Compare/Capture : Capture ( capture the counts when Timer stops )

Interrupt : Capture Count ( an Interrupt will assert when Count is capture )

Timer Starts (start counting) & Reloads(from 0) on the Rising Edge of Ultrasonic Module's Echo Pin then Stop(stop counting) & Count(counts the ticks from start to stop) on the Falling Edge, then the Interrupt occurs( In the ISR number of counts is converted into time, distance is updated).

The Timer will start again, when a new Echo Pulse comes !

If you want to make following projects using PSoC 4:

1. Obstacle Avoiding Robots
2. Scanning Object Shape
3. Detecting Motion at a given distance

This mini project will be handy ! Using another Timer in continuous mode, the Trigger Pin can be periodically fired, thus eliminating CyDelay from code to free up the CPU !

Code

main c

/* ========================================
 *
 * Copyleft by Shahariar,2015
 * All Rights Released
 * OPEN SOFTWARE, NO WARRENTY 
 *
 * DODGY BROTHERS C CODING Inc.  
 * BUG may appear in Future !!!
 * Non-Precision (3cm -200 cm) UltraSonic Ranger,
 * ========================================
*/

#include <project.h>

// Initial time ,set  here
int16 i =0;
int distance=0;

//CY ISR is a macro for interrupt handling
// http://www.cypress.com/go/an90799 for detalis
CY_ISR(Timer_ISR_handler)
{
    // at 1MHz Timer clock each count is 1 micro Second
    Timer_ClearInterrupt(Timer_INTR_MASK_CC_MATCH);
    i= Timer_ReadCounter();    
    
    // from HC 04 Ultra Sonic module's datasheet, each 58 uS = 1 cm
    
    distance =i/58;  // in cm
    //distance = i/148; // in inch
    // please note that measured distance above 200 cm is not reliable
    // limit max distance for bug free systems
   // if (distance>200) {distance =200;}
}

int main()

{
// Start Timer
    Timer_Start();
// Enable Global Interrupt and start ISR  
    CyGlobalIntEnable; 
    ISR_StartEx(Timer_ISR_handler);
    //SetTime_ISR_Start();
    
//  Supply 5 Vdd to LCD display from MCU and power up Back Light  
    Power_Up_LCD_Pin_1_Write(1);
    Back_Light_On_N_Write(0);
    Back_Light_On_P_Write(1);

// Start LCD display    
    LCD_Char_Start();
    LCD_Char_DisplayOn();
    
             
        for(;;)
        {
    // for proper application, delay should not be used, 
    // instead a preiodic interrupt or a function call is recommended
    CyDelay(500);
    
    // Triggers the Ultra Sonic Sensor 
    Trigger_Write(1);
    LED_Write(1);
    CyDelayUs(10);
    // for 10 uS Trig pin is kept high to start ultra sonic distance module
    // the blue led will blink for a moment druing each trigger
    // distance updates (about) twice time per second
    Trigger_Write(0);
    LED_Write(0);
    
    LCD_Char_ClearDisplay();
   
    
    LCD_Char_Position(0,0);
    LCD_Char_PrintString("PSoC SonicRANGER");
    
    LCD_Char_Position(1,0);
    LCD_Char_PrintString("Distance: ");
    
    LCD_Char_Position(1,10);
    LCD_Char_PrintNumber(distance);
    
    LCD_Char_Position(1,14);
    LCD_Char_PrintString("cm");
    
    
    
}
          
}
/* [] END OF FILE */

Credits

Shahariar

74 projects • 265 followers

"What Kills a 'Great life' is a 'Good Life', which is Living a Life Inside While Loop"

Thanks to Alan Hawse .

PSoC 4: Measuring Distance with HCSR-04 and CY8CKIT-049 4200

Things used in this project

Hardware components

Story

So How does it work ?

Schematics

Connections

Ultrasonic%20Ranger.cydsn.zip

Schematic

Code

main c

Credits

Shahariar

Comments

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PSoC 4: Measuring Distance with HCSR-04 and CY8CKIT-049 4200

PSoC 4: Measuring Distance with HCSR-04 and CY8CKIT-049 4200

Things used in this project

Hardware components

Story

So How does it work ?

Schematics

Connections

Ultrasonic%20Ranger.cydsn.zip

Schematic

Code

main c

Credits

Shahariar

Comments

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