linpoyu / ultrasound

ultrasound

ultrasound's Issues

Heart signal(calculate frequency: 1.24Hz)

Plot heart signal:

FFT:(Can't find frequency band at 1.24Hz)

Arduino due(Programming port V.S. Native USB port)

Programming port(function call)

1. Sample rate is unstable
2. Baud Rate is 115200

Programming port(while loop)

1. Sample rate is unstable
2. Baud rate is 115200

Native USB port(function call)

1. Sample rate is stable
2. BaudRate is over 115200

Native USB port(while loop)

1. Sample rate is stable
2. BaudRate is over 115200

When my signal inputs to arduino(analog port A0), I can't see signal.

Arduino Interval test( Programming port micros() V.S. Native USB port micros() )

Programming port micros()

Native USB port micros()

Tektronix DPO3034 scope

It mentions setting a trigger for a single sample instead of continuous acquisition.
(https://forums.ni.com/t5/SignalExpress/Multiple-measurement-Tektronix-DPO-3034-lag-between-two-channels/td-p/2707107)

Antenna

上次meeting老師說要在低頻一點，要可穿進人的身體，但沒有說要在什麼範圍，於是我有上網找到資料，是關於多少頻率才能穿進人的身體，大概幾百MHz就能穿過軟骨的部分。

About antenna(發送頻率越低，長度會增加(λ/2))

Low-frequency antenna(100MHz~999MHz)

• Length is too long(指向性天線會因頻率越低，而長度和體積都滿大的)

• There are few antennas on online store website

High-frequency antenna(1GHz~15GHz)

• Volume is small(體積面積會較小)

• There are a lot of antennas on online store website

因上述的理由，所以決定要買GHz的天線。
PS:老師有推薦的天線網站可以購買天線嗎? 老師要是有任何問題，再回覆給我，謝謝
林柏佑同學

ADC on Matlab(plot: 1kHz sin siganl and FFT)

sin signal(1kHz)

sin signal after fft

sin signal after fft(zoom in)

test1 sample rate

ADC read interval

6 microseconds swing ±1 (on arduino)

2 microseconds swing ±1(on matlab)
send 10000 data to PC by arduino
2 microseconds : 80%
1 microseconds : 19%
3 microseconds : 1%

I use SampleRateTest2 to know how many sample rate(208989、208990)

#include <stdint.h>

const int MaxSampleCount = 3000;
char buffer[100];

void setup() {
SerialUSB.begin(0);
while(!SerialUSB);
}

void loop() {
SamplingRateTest2(); // Test samples per second (while loop)
}

void SamplingRateTest2()
{
int sampleCount = 0;
int sensorValue;
int startTime = millis();

while(millis() - startTime < 1000)
{
sensorValue = analogRead(A0);
sampleCount++;
}
sprintf(buffer, "%d\r\n", sampleCount);
SerialUSB.print(buffer);
}

plot FFT

plot FFT (log frequency)

If we know time , we can figure out sample rate(Performance is not good in FFT plot.)

Matlab code:
figure out Fs.txt

plot:

FFT:

test2 sample rate

arduino ADC sidelobe(Native USB port: Baud rate 250000)

Sin Wave 1kHz

Sin Wave 1kHz after FFT

arduino ADC sidelobe(Programming port)

Arduino adc sin wave(1kHz)

Signal after FFT(1kHz sine wave)

Periodogram using fft(1kHz sine wave)(log scale)

Arduino adc sin wave(40kHz)

Periodogram using fft(40kHz sine wave)(log scale)