ultrasonic phased array

marionboynton · September 26, 2019, 11:42am

Hello
I have the following code for Arduino mega to output 40 kHz square waves at the analog pins. I need to apply specific phase delays for the signals at each pin though and am struggling to find out how to do this. Any help would be appreciated.
Thanks!

byte TP = 0b10101010; // Every other port receives the inverted signal

void setup() {

DDRF = 0b11111111; // Set all analog ports to be outputs
DDRK = 0b11111111; // Set all analog ports to be outputs
// Initialize Timer1

noInterrupts(); // Disable interrupts

TCCR1A = 0;

TCCR1B = 0;

TCNT1 = 0;

OCR1A = 200; // Set compare register (16MHz / 200 = 80kHz square wave -> 40kHz full wave)

TCCR1B |= (1 << WGM12); // CTC mode

TCCR1B |= (1 << CS10); // Set prescaler to 1 ==> no prescaling

TIMSK1 |= (1 << OCIE1A); // Enable compare timer interrupt

interrupts(); // Enable interrupts

}

ISR(TIMER1_COMPA_vect) {

PORTF = TP; // Send the value of TP to the outputs
PORTK = TP;
TP = ~TP; // Invert TP for the next run

}

void loop() {

// Nothing left to do here :)

}

PerryBebbington · September 26, 2019, 3:35pm

Hello marionboynton,
Welcome to the forum.

When you read 'how to use this forum - please read', what did it say under item #7?

Please go back and modify your post accordingly, you are more likely to get helpful, friendly answers that way.

TomGeorge · September 26, 2019, 3:58pm

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html .
Then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.

Thanks.. Tom..

DrDiettrich · September 26, 2019, 4:39pm

What's your specific problem?

MarkT · September 26, 2019, 5:53pm

Each timer can have a different phase, but each timer controls 2 or 3 analog pins typically, so certain pins have
to stay in phase (although they can be in antiphase on the same timer). Reading the hardware timers sections of the ATmega2560 will explain all this in detail.

DrDiettrich · September 26, 2019, 6:21pm

What's the intended phase shift?

Ballscrewbob · September 27, 2019, 1:13pm

@marionboynton

OTHER POST DELETED

Do NOT cross post as it wastes peoples time and effort to help you.

Could you please READ THIS to get the best out of the forum before adding any further posts.

Bob.

johnwasser · September 27, 2019, 2:01pm

Use the PINx registers to toggle outputs.

// These are the bit masks for each pair of pins in PORTF and PORTK
const uint16_t Channels[8] = {0xC000U, 0x3000U, 0x0C00U, 0x0300U, 0x00C0U, 0x0030U, 0x000CU, 0x0003U};


// In each of the 32 phases, OR together the channels that toggle at that phase offset.
// The actual phase offsets will depend on processor timing so I just put the 8 channels 
// in randomly.
const uint16_t Phases[32] =
{
  Channels[0] | Channels[4], 0, 0, Channels[1] | Channels[5], 0, 0, 0, 0,
  0, Channels[2], Channels[3], 0, 0, 0, 0, 0,
  0, 0, Channels[6] | Channels[7], 0, 0, 0, 0, 0,
  0, 0, 0, 0, 0, 0, 0, 0
};

void setup()
{
  DDRF = 0b11111111; // Set all analog ports to be outputs
  DDRK = 0b11111111; // Set all analog ports to be outputs
  PORTF = 0b10101010;
  PORTK = 0b10101010;


  // Initialize Timer1


  noInterrupts(); // Disable interrupts


  TCCR1A = 0;
  TCCR1B = 0;
  TCNT1 = 0;


  OCR1A = 200; // Set compare register (16MHz / 200 = 80kHz square wave -> 40kHz full wave)


  TCCR1B |= (1 << WGM12); // CTC mode
  TCCR1B |= (1 << CS10); // Set prescaler to 1 ==> no prescaling
  TIMSK1 |= (1 << OCIE1A); // Enable compare timer interrupt


  interrupts(); // Enable interrupts
}


ISR(TIMER1_COMPA_vect)
{
  // Writing bits to the PINx register will toggle the output bits.


  // Unroll the loop so everything will be constants.  This should allow the compiler to 
  // optimize each line into a single instruction.  You can add NOP instructions between 
  // phase offsets to increase the offsets.  As long as the ISR doesn't take longer than a 
  // few microseconds it should be OK.


  PINF = Phases[0] >> 8;
  PINK = Phases[0];
  
  PINF = Phases[1] >> 8;
  PINK = Phases[1];
  
  PINF = Phases[2] >> 8;
  PINK = Phases[2];
  
  PINF = Phases[3] >> 8;
  PINK = Phases[3];
  
  PINF = Phases[4] >> 8;
  PINK = Phases[4];
  
  PINF = Phases[5] >> 8;
  PINK = Phases[5];
  
  PINF = Phases[6] >> 8;
  PINK = Phases[6];
  
  PINF = Phases[7] >> 8;
  PINK = Phases[7];
  
  PINF = Phases[8] >> 8;
  PINK = Phases[8];
  
  PINF = Phases[9] >> 8;
  PINK = Phases[9];
  
  PINF = Phases[10] >> 8;
  PINK = Phases[10];
  
  PINF = Phases[11] >> 8;
  PINK = Phases[11];
  
  PINF = Phases[12] >> 8;
  PINK = Phases[12];
  
  PINF = Phases[13] >> 8;
  PINK = Phases[13];
  
  PINF = Phases[14] >> 8;
  PINK = Phases[14];
  
  PINF = Phases[15] >> 8;
  PINK = Phases[15];
  
  PINF = Phases[16] >> 8;
  PINK = Phases[16];
  
  PINF = Phases[17] >> 8;
  PINK = Phases[17];
  
  PINF = Phases[18] >> 8;
  PINK = Phases[18];
  
  PINF = Phases[19] >> 8;
  PINK = Phases[19];
  
  PINF = Phases[20] >> 8;
  PINK = Phases[20];
  
  PINF = Phases[21] >> 8;
  PINK = Phases[21];
  
  PINF = Phases[22] >> 8;
  PINK = Phases[22];
  
  PINF = Phases[23] >> 8;
  PINK = Phases[23];
  
  PINF = Phases[24] >> 8;
  PINK = Phases[24];
  
  PINF = Phases[25] >> 8;
  PINK = Phases[25];
  
  PINF = Phases[26] >> 8;
  PINK = Phases[26];
  
  PINF = Phases[27] >> 8;
  PINK = Phases[27];
  
  PINF = Phases[28] >> 8;
  PINK = Phases[28];
  
  PINF = Phases[29] >> 8;
  PINK = Phases[29];
  
  PINF = Phases[30] >> 8;
  PINK = Phases[30];
  
  PINF = Phases[31] >> 8;
  PINK = Phases[31];
}


void loop()
{
  // Nothing left to do here :)
}

jremington · September 27, 2019, 4:21pm

I need to apply specific phase delays for the signals at each pin

Please state the specific delays required and how many pins will be controlled.

There are only 400 processor clock cycles (at 16 MHz) in one cycle of 40 kHz, so the standard AVR-based Arduinos may not be a good choice.

TomGeorge · September 28, 2019, 10:19am

Hi,
What is the application that you need to apply phase shifts?

Thanks.. Tom..

DrDiettrich · September 28, 2019, 11:23am

How long can zombies continue living?

marionboynton · September 28, 2019, 11:29am

hi Tom the phase shifts are so that when emitting the square wave signals from several transducers I can focus the resulting beam in a region of constructive interference.

TomGeorge · September 28, 2019, 12:05pm

Hi,
Squarewaves won't produce an interference pattern, sinewaves will.

There will be many regions of constructive interference, are you trying to make an ultrasonic cannon?
What are you using as ultrasonic transmitters?
How much phase/time shift are you trying to get?

Tom..

marionboynton · September 28, 2019, 1:32pm

the square waves are to power the ultrasonic transmitters which resultantly produce ultrasound (longitudinal sin) waves.

johnwasser · September 28, 2019, 1:46pm

Wouldn't just arranging the transducers in a circle cause them to constructively interfere along the central axis? That would be much easier than a phased array if size is not an issue.

DrDiettrich · September 28, 2019, 1:51pm

Consider which minor phase shifts are required for generating the intended focus, and which phase shifts can be provided by a 16MHz controller. I'd recommend a much faster controller for your project. But for now you can find out how to code the generation of multiple square waves with time shifts.

jremington · September 28, 2019, 3:39pm

the phase shifts are so that when emitting the square wave signals from several transducers I can focus the resulting beam in a region of constructive interference.

Yes, that is the basic theory behind common practice, except of course, the transducers are assumed to emit sine waves.

If you can't provide quantitative answers to the questions we are asking, this project may be too difficult for you.

The important details of focusing by ultrasonic phased arrays are discussed in this excellent and comprehensive tutorial: Olympus Phased Array Tutorial, Learn About Ultrasonic Phased Array

DrDiettrich · September 28, 2019, 5:49pm

Multiple (acoustic) waves can accumulate in certain places, and extinct each other to some degree somewhere else.

Likewise a single source can be recorded in a number of locations, so that the required phase shift for all transmitters in those locations can be determined. This should work for all waveforms, be sine or square or something distorted in between these, provided equal speed of sound.

marionboynton · September 29, 2019, 2:37pm

after spending torturous hours trying to learn timers and interrupts I think I got it in a much simpler way!

#include <util/delay.h>

void setup() {
DDRA = 0b11111111; //outputs
DDRB = 0b11111111;
DDRC = 0b11111111;
}

void loop() {
noInterrupts();

PORTA = 0b10101010; 
PORTC = 0b10101001;
_delay_us(2);
PORTC = 0b10101010; 
_delay_us(10.5);
PORTA = 0b01010101;
PORTC = 0b01010110; 
_delay_us(2);
PORTC = 0b01010101; 
_delay_us(10.5);
interrupts();

}

Topic		Replies	Views
Apply delayed signal to ultrasonic transducers Programming	10	1332	May 5, 2021
Set Multiple pins with phased shift Programming	3	842	May 5, 2021
Control multiple digital pins General Guidance	102	19811	May 5, 2021
About phase delay circuit General Guidance	5	759	May 5, 2021
Use Arduino MEGA generate 40kHz multiple square wave signal with 10 phase Programming	14	660	May 31, 2023

ultrasonic phased array

Related topics