Transmitting data from Arduino UNO into MATLAB but getting a lot of NaNs and numbers with missing digits - matlab

Question

I'm collecting degree data from an encoder using an Arduino Uno, and then sending that data into MATLAB using USB. In order to get velocity of rotation as well, I'm generating and sending a timestamp after every degree data point from the Arduino into MATLAB. The data is generated flawlessly on the Arduino side--there's nothing wrong on the Serial Monitor.
In MATLAB, however, my data matrices fill up with quite a few NaNs, as well as the occasional integer with a missing first digit. For example, instead of 216 degree, I get 16 degrees coming through, or instead of 7265900 microseconds, I get 265900 microseconds coming through.
I've been able to solve the issue of losing time data by using Arduino's millis() clock instead of its micros() clock and by adding a 50 millisecond delay after the encoder reading. The problem of degree data loss goes away if I increase the delay after the millis() clock, but then degree data acquisition becomes too slow to be useful.
Any help would be much appreciated!
Code pasted below. First the Arduino code, then the MATLAB code.
Thank you!
David
#include <Adafruit_LEDBackpack.h>
#include <Adafruit_GFX.h>
#include <gfxfont.h>
#include <SPI.h> //Include the SPI library in this sketch.
#include <Wire.h> // Enable this line if using Arduino Uno, Mega, etc.
//#include <TinyWireM.h> // Enable this line if using Adafruit Trinket, Gemma, etc.
#include "Adafruit_LEDBackpack.h"
#include "Adafruit_GFX.h"
Adafruit_7segment matrix = Adafruit_7segment();
//Variables for SPI rotary encoder
boolean knob_detected = false;
byte slave_select = 10; //Slave select pin.
byte mosi = 11; //MOSI pin.
byte miso = 12; //MISO pin.
byte spi_clock = 13; //Clock pin.
byte read_counter = 96;
byte write_mode0 = 137;
byte write_mode1 = 144;
byte count1;
byte count2;
int count;
int val;
int button = 7;
int b = 0;
int degree;
int absolute;
unsigned long time;
// SETUP //
void setup() {
//Connect the 4 communication pins between the Arduino and the quadrature counter.
#ifndef __AVR_ATtiny85__
Serial.begin(9600);
//Serial.println("7 Segment Backpack Test");
#endif
matrix.begin(0x70);
pinMode(slave_select, OUTPUT);
pinMode(mosi, OUTPUT);
pinMode(miso, INPUT);
pinMode(spi_clock, OUTPUT);
// pinMode(button,INPUT);
SPI.begin(); //Begin SPI communication.
SPI.setBitOrder(MSBFIRST); //Bytes read into SPI will be read in MSB style.
SPI.setDataMode(SPI_MODE0); //Set the data to shift on the low clock phase with normal (non-inverted) clock polarity.
digitalWrite(slave_select, HIGH); //Close the SPI communication port.
SPI.setClockDivider(SPI_CLOCK_DIV128); //Set the SPI clock to 125 kHz (This can be changed).
digitalWrite(slave_select, LOW); //Set slave select low to enable communication.
SPI.transfer(write_mode0); //Select mode 0 for modifying.
SPI.transfer(0b01000011); //Write to mode 0: Synchronous Index, disable index, range-limit count mode, x4 quadrature.
digitalWrite(slave_select, HIGH); //Set slave select high to disable communication
digitalWrite(slave_select, LOW); //Set slave select low to enable communication
SPI.transfer(write_mode1); //Select mode 1 for modifying.
SPI.transfer(2); //Write across a 0b01 to mode1 to enable 2 byte data transfers
digitalWrite(slave_select, HIGH); //Set slave select high to disable communication
Serial.begin(9600); //Set the baud rate for serial data transmission.
//Serial.println("READY"); //Print "READY" to the serial line to indicate that initialization is complete.
}
// MAIN LOOP //
void loop() {
digitalWrite(slave_select, LOW); //Set slave_select pin low to begin tranmission .
SPI.transfer(read_counter); //Read from the read_counter register.
count1 = SPI.transfer(0); //Send a null transfer to read byte1 values.
count2 = SPI.transfer(0); //Send a null transfer to read byte2 values.
digitalWrite(slave_select, HIGH); //Set slave_select high to end transmission.
count = word(count1, count2); //Type cast the 2 bytes as a word.
degree = count / 4;
absolute = abs(degree);
//Send back the value of the register over the serial line.
b = digitalRead(button);
if (b == HIGH) {
digitalWrite(absolute,LOW);
}
else {}
if (absolute == LOW)
{
absolute = 0;
}
else {}
Serial.println(absolute); //Send back the value of the register over the serial line.
matrix.print(absolute,DEC);
matrix.writeDisplay();
delay(50); //Pause for 50 milliseconds before re-looping.
time = millis();
Serial.println(time);
delay(10);
}
clear all;
close all;
clc;
delete(instrfind); %delete connected ports
p=getserialport;
[m,n] = listdlg('PromptString','Select Your Bluetooth device:','SelectionMode','single','ListString',p);
com=cell2mat(p(m));
s=serial(com);
fopen(s);
csd = figure;
set(csd,'Name','Plotting Arduino Data on MATLAB','NumberTitle','off'); % open Figure
t=1:100;% total Figure
hAx(1) = subplot(211);
hLine(1) = line('XData',t, 'YData',nan(size(t)), 'Color','b', 'Parent',hAx(1));
xlabel('Samples'), ylabel('Degrees');
hAx(2) = subplot(212);
hLine(2) = line('XData',t, 'YData',nan(size(t)), 'Color','b', 'Parent',hAx(2));
xlabel('Samples'), ylabel('Velocity');
set(hAx, 'Box','on', 'YGrid','on');
axis(hAx(1),[0,100,0,100]);
axis(hAx(2),[0,100,0,100000]);
d=zeros(1,100); %buffer of 100 elements
sm=zeros(1,10); %buffer of 10 elements
t10=zeros(1,10); %buffer of 10 elements
t100=zeros(1,100); %buffer of 100 elements
while(1)
j=1;
while(j<=10)
flushinput(s);
sc=(fscanf(s));
if(length(sc)<6) %1000 degree units = 6 char (was <7 for micros() clock)
sm(j)=str2double(sc);
else %i.e. else, if a timestamp (more than 7 chars)
t10(j)=str2double(sc);
j=j+1;
end
end
t100 = [t100,t10];
t100 = t100(11:end);
d=[d,sm]; %Add new Samples
d=d(11:end); %Remove old Samples
%d(end)
set(hLine(1), 'YData',d); %draw Degrees
set(hLine(2), 'YData',t100); %draw Velocity (currently just timestamps)
drawnow %# force MATLAB to flush any queued displays
end
(getserialport function defined by the following m-file)
function x=getserialport
serialInfo = instrhwinfo('serial');
x=serialInfo.SerialPorts;
end