Reading Data from Serial Port and Plotting in Real Time - matlab

Question

I am looking to take in data from a temperature sensor on an Arduino Uno board and have matlab store the data while also plotting the data on a graph in real time to monitor sensor changes. This will eventually be implemented with a different sensor and this more of a proof of concept. I have two issues currently troubling me:
1) I need to be gathering the data points 1000x a second (which my current code cannot do)
2) After several seconds of monitoring the data a great deal of noise enters the system
Here is my matlab code
SerialPort = 'com6';
s = serial(SerialPort, 'BaudRate', 250000, 'DataBits', 8);
fopen(s);
voltage = 0;
t = 0;
y = 1;
voltage = fscanf(s);
VoltageValue(y,1)=str2double(voltage);
h = animatedline(t,VoltageValue(y,1));
xlim([0 1000]);
ylim([100 200]);
tic
while t <= 1000
voltage = fscanf(s);
VoltageValue(y,1)=str2double(voltage);
addpoints(h, t, VoltageValue(y,1));
t= t+1;
y= y+1;
drawnow
end
toc
fclose(s);
delete(s);
clear s;
Here is my arduino code
int tmppin = 0;
void setup() {
// put your setup code here, to run once:
Serial.begin(250000);
pinMode(tmppin, INPUT);
}
void loop() {
// put your main code here, to run repeatedly:
int tempreading = analogRead(tmppin);
Serial.println(tempreading);
}

Answer 1

From what I have tried, the serial communication at 38400bd is enough to transmit an int at 1kHz. You can use 115200bds; your speed of 500000bds is not supported, even if it usually works.
The ADC will have no problem with 1000Hz. The Arduino command analogRead works at 10kHz; and if you would access register of atmel MCU directly, you could speed up analogRead to 100kHz.
Your code is slowed down with drawnow. You dont need to refresh at 1kHz; if you refresh at 10Hz, it will be real time for your eye.
In arduino sketch you should put a delay(1) (1ms), so you know the serial buffer wont get full.

Answer 2

also , to speedup the transfer speed, sending the data as binary will help a lot the Serial.println(tempreading); you used sends data as string. meaning it will send 6 characters each time. (5 characters + the CR). sending as binary will need only 2 bytes.
; a 3X speed increment already.
To send data as binary in arduino , use
serial.write(data_to_send>>8); //send most significant byte
serial.write( data_to_send && f); //send least significant byte