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High accuracy SRF04 Sonar distance chip for remote RS232

 
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Arizona Chris



Joined: 20 Dec 2014
Posts: 69
Location: Arizona

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High accuracy SRF04 Sonar distance chip for remote RS232
PostPosted: Fri Sep 04, 2015 7:47 pm     Reply with quote

Greetings all,

Been doing a lot of work with remote sensors that take the computational loading off the main processor to keep my ROM space in check. This one uses a PIC16F628 for the sensor chip, and here I am using as an example to send it to a 16F887 chip. I can use this PIC now that I have my wonderful Mach X programmer! ;)

The key here is to account for what happens when a sensors 232 data stops transmitting due to a fault. the getc command will of course wait forever for a 232 input, and your main processor locks up. But by using the function khbit we can prevent this. I set a half second delay in if no 232 input is recieved. I purposly used a non UART input to show that you can have many sensors on one master chip and do it with a software 232. Thanks for looking.

You can see schematics, photos of the setup, and layouts on my web page here:

http://www.schursastrophotography.com/PICprojects/SonarChip090315.html

First the sonar chip code

Code:


//****************************************************************************
//Chris Schur
//(Sonar Chip 16F628)
//Date:  8/23/15
//****************************************************************************

/*Description of this Program:

This program sends raw serial data at 9600kb out to be reciveved by the main
processor every 100ms. */


//I/O Designations ---------------------------------------------------
// RA0:  sonar TRIG Output
// RA1:  sonar Pulse Input
// RA2: 
// RA3: 
// RA4:  (Open Collector output)
// RA5:  (MCLR)
// RA6:  Xtal  Output
// RA7:  Xtal  Input

// RB0: rs232 output to main uC
// RB1:  GREEN LED output
// RB2:  BLUE LED output
// RB3: 
// RB4: 
// RB5: 
// RB6: 
// RB7: 


//--------------------------------------------------------------------

//Include Files:
#include <16F628.h>  //Normally chip, math, etc.  used is here.

//Directives and Defines:
//#device ADC=10  //Set ADC when used to 10 bit = 0 - 1023
#fuses NOPROTECT,HS,NOWDT   //xtal is used
#use delay(crystal=10MHz)   //xtal speed
#use fast_io(ALL)          //must define tris below in main when using this

//for LCD:
//#use rs232(baud=9600, xmit=Pin_B3, bits=8, parity=N,stream=SERIALNH)
//for data out to main processor:
#use rs232(baud=9600, xmit=Pin_B0, bits=8, parity=N,STREAM=SONAR)


//****************************************************************************
//Global Variables:
int16  sonarmeas = 0;     //distance in inches from internal horns 
float sonardist = 0;
int highbyte,lowbyte;   //high byte and low byte for serial data

//****************************************************************************
 
   
//Functions/Subroutines, Prototypes:

int16 sonar1 (int16 sonarpulse, int16 sonartime, int16 d); //get sonar dist.

//****************************************************************************
//-- Main Program
//****************************************************************************

void main(void) {

   // Set TRIS I/O directions, define analog inputs, compartors:
      set_tris_A(0b01111110);
      set_tris_B(0b11110000);
     
      //(analog inputs digital by default) 

   //Initialize variables and Outputs:  --------------------------------------
   output_low(Pin_B0);  //status off
   output_low(Pin_B1);
   output_low(Pin_B2);
   output_low(Pin_B3);
   
   //Setup for timers, PWM, and other peripherals:
   
   //----------------------------------------------------------------

//MAIN LOOP:

while (true)   {

//get sonar current dist:
sonarmeas = sonar1(0,0,0);  //call up sonar1 function, variables start at 0
//sonardist = (float) sonarmeas / 155;  //convert to inches-change typedef

//Next send the raw measurement data out serially:
//Convert to two 8 bit integers to send:
lowbyte = MAKE8(sonarmeas,0);
highbyte = MAKE8(sonarmeas,1);

delay_ms(100);     //space between trig pulses

//trig pip for oscilloscope  to see data clearly
output_high(Pin_B2);
delay_us(10);
output_low(Pin_B2);

//send data serially:
   fputc(lowbyte,SONAR);
   //delay_ms(5);
   fputc(highbyte,SONAR);
   //delay_ms(10);
   

    } 
 
}

//********* Functions which have prototypes at top of program ****************
int16 sonar1 (int16 sonarpulse, int16 sonartime, int16 d)  {

setup_timer_1( T1_INTERNAL | T1_DIV_BY_2 );//must be inside function!!!!!

//max 52.6ms  = 65000 x .8uS res per count

output_high(Pin_A0);   //send trig pulse
delay_us(10);
output_low(Pin_A0);

delay_us(200); //this delay is added to end 70uS before the rising edge of echo
         
//start isr to time out if no echo:
SET_TIMER1(0);      //reset to zero on timer counter.
//clear_interrupt (INT_TIMER1);  //you must do this or it will have int allready.
//enable_interrupts (INT_TIMER1);  //turn on TIMER1 interrupt

//now look for L to H transition:
while (input(Pin_A1) == 0);  //wait for 0 to 1

//reset timer:
SET_TIMER1(0);      //reset to zero on timer counter.

//now look for H to L transition:
while (input(Pin_A1) == 1);  //wait for 1 to 0

//turn off isr:
//disable_interrupts (INT_TIMER1);  //turn off TIMER1 interrupt

sonarpulse = get_timer1();
sonartime = sonarpulse * .8;  //actual uS pulse width

if (sonartime > 18000)  //max range is 18ms = 116" = 9.7 feet.
      sonartime = 18000;    //set to max if beyond range.
     
//d = sonartime / 155;   //18000/155= 116;

return sonartime;

}




Next here is the reciver code on an 887 chip

Code:

//****************************************************************************
//Chris Schur
//(sonar recieve 16F887)
//Date:  8/28/15
//****************************************************************************

/*Description of this Program:

This short program recieves the 9600 kb serial data from the sonar chip and converts
it to a distance in inches with two decimal places, then sends it to the serial LCD.*/


//I/O Designations ---------------------------------------------------
// RA0:  (AN0)  Sonar serial data input
// RA1:  (AN1)
// RA2:  (AN2)
// RA3:  (AN3)
// RA4:  (Open Collector output)
// RA5:  (AN4)
// RA6:  OSC OUT
// RA7:  OSC IN

// RB0:  (AN12,EXT INT)  Status LED output
// RB1:  (AN10)  LCD output
// RB2:  (AN8) 
// RB3:  (AN9)
// RB4:  (AN11)
// RB5:  (AN13)
// RB6: 
// RB7: 

// RC0: 
// RC1: 
// RC2: 
// RC3:  (SCLK)
// RC4:  (SDA)
// RC5: 
// RC6: 
// RC7:

// RD0:
// RD1:
// RD2:
// RD3:
// RD4:
// RD5:
// RD6:
// RD7:

// RE0:   (AN5)
// RE1:   (AN6)
// RE2:   (AN7)
// RE3:   (MCLR INPUT - Pull High)

//--------------------------------------------------------------------

//Include Files:
#include <16F887.h>  //Normally chip, math, etc.  used is here.

//Directives and Defines:
#device ADC=10  //Set ADC when used to 10 bit = 0 - 1023
#fuses NOPROTECT,HS,NOWDT   //xtal is used
#use delay(crystal=10MHz)   //xtal speed
#use fast_io(ALL)          //must define tris below in main when using this

//for LCD:
#use rs232(baud=9600, xmit=Pin_B1, bits=8, parity=N,stream=SERIALNH)

//For reciving sonar data on pin A0:
#use rs232(baud=9600, rcv=Pin_A0, bits=8, parity=N, DISABLE_INTS,stream=SONAR)
//Note: the "disable_ints is critical, turns off constant barrage of interrupts
//during the aquisition of data in the get command so timing is not affected.

//NO_ANALOGS is default in device file...(All I/Os are digital)


//***Global Variables:********************************************************
int16  sonarmeas = 0;     //distance in inches from internal horns 
float sonardist = 0;
int highbyte,lowbyte;   //high byte and low byte for serial data
int1 sonarbit;  //incoming data verification bit
int16 sonartimeout;  //counts of kbit delay increrments

//***Functions/Subroutines, Prototypes:***************************************
//Clears LCD Display:
void LCDCLR()  {
   fputc(0xFE,SERIALNH);   //Command Prefix
   fputc(0x51,SERIALNH);   //Clear screen
}

//Sets LCD to line 2 start point
void LCDLN2()  {
   fputc(0xFE,SERIALNH);   //Command Prefix
   fputc(0x45,SERIALNH);   //set cursor command
   fputc(0x40,SERIALNH);   //Set cursor to next line, pos 40 = start line 2
}

void GETSONAR(void);

//****************************************************************************
//***-- Main Program*********************************************************

void main(void) {

   // Set TRIS I/O directions, define analog inputs, compartors:
      set_tris_A(0b10111111);
      set_tris_B(0b11111100);
      set_tris_C(0b11111111);
      set_tris_D(0b11111111);
      set_tris_E(0b1111);

   //Initialize variables and Outputs:  --------------------------------------
 
   
   //Setup for timers, PWM, and other peripherals:
   
   //----------------------------------------------------------------



//Main Program


while (true)   {

GETSONAR();  //go get sonar data serially
     
  LCDCLR();   //clear screen
   delay_ms(10);
   fprintf(SERIALNH,"%f"sonardist);  //NOTE: %Lu in command is int16 only output
   delay_ms(250);
 
 output_high(Pin_B0);
 delay_ms(25);
 output_low(Pin_B0);
 delay_ms(25);

    }  //while
 
}  //main

//********* Functions which have prototypes at top of program ****************

void GETSONAR(void)  {
//test loop to see if data has come in lasting maximum of 1/2 second:

sonartimeout = 0;  //reset timeout

while (!kbhit(SONAR) && (++sonartimeout < 50000))  //half second wait IF NO SIGNAL
   delay_us(10);
   
if (kbhit(SONAR))  {   //We have a signal
   lowbyte = fgetc(SONAR);
   highbyte = fgetc(SONAR);
   sonarmeas = MAKE16(highbyte,lowbyte);  //RAW
   sonardist = (float) sonarmeas / 155;  //inches with 2 decimals
      }
}   

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