HELP! Can't find bugs in the code of my POV (mirrored display)

Hello! I need help in debugging the code for my POV.
It displays right string but it is mirrored :frowning:

check this:

that’s my output.

I got the codes from here:

I already edit the for loops of the code. please take a look, it is quite short.

 // defining the alphabet
 #include "font.h"
 
 // define the Arduino LED pins in use
 const int LEDpins[] = {
   6,5,4,3,2,1,0};
 
 // number of LEDs
  const int charHeight = sizeof(LEDpins);
  const int charWidth = 5;
 
 
 
 // sensor setup
 const int sensorPIN = 12;  // define the Arduino sensor pin

//  boolean sensorFlag = false;  // stores sensor state
  int sensVal;  // variable to store the value coming from the sensor
 
 const char textString[] = "APPLAUSE";
 
 void setup()
 {
   pinMode(13, OUTPUT);
    pinMode(0 , OUTPUT);
   pinMode(1, OUTPUT);
    pinMode(2, OUTPUT);
     pinMode(3, OUTPUT);
    pinMode(4, OUTPUT);
    pinMode(5, OUTPUT);
    pinMode(6, OUTPUT);
 
   
  //   Serial.begin(9600);
 }
 
 void loop()
 {
   // turn on Led for a circle in middle and proof that arduino is powered
    digitalWrite(13, HIGH);   // set the LED on  
    
     
  sensVal = analogRead(sensorPIN);  // read the Hall Effect Sensor  
 
 
 
 //    Serial.println(sensVal);
// delay(500 );  
// had difficulty here
// since it is a switch hall switch probably shoiuld just do digital read

 if (sensVal  == 0) {
   // printing every letter of the textString
   for (int k=0; k<sizeof(textString); k++){
     printLetter(textString[k]);
   }

 }
 }
 
 
 
 
 void printLetter(char ch)
 {
   // make sure the character is within the alphabet bounds (defined by the font.h file)
   // if it's not, make it a blank character
   
    
   
   if (ch < 32 || ch > 126){
     ch = 32;
   }
   // subtract the space character (converts the ASCII number to the font index number)
   ch -= 32;
   // step through each byte of the character array
   for (int i=0; i<charWidth; i++) {
     byte b = font[ch][i];
     
 
 
     // bit shift through the byte and output it to the pin
     for (int j=charHeight; j>=0; j--) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     
     }
     // space between columns
 
 delayMicroseconds(900);
   }
   //clear the LEDs
 digitalWrite(0 , LOW);   // set the LED on
digitalWrite(1 , LOW);   // set the LED on
digitalWrite(2 , LOW);   // set the LED on
digitalWrite(3 , LOW);   // set the LED on
digitalWrite(4 ,LOW);   // set the LED on
digitalWrite(5 , LOW);   // set the LED on
digitalWrite(6 , LOW);   // set the LED on
   
   // space between letters
   delayMicroseconds(2500);
 
 }

for the FONT.H

const unsigned char font[95][5] = {
            {0x00,0x00,0x00,0x00,0x00},   //   0x20 32
            {0x00,0x00,0x6f,0x00,0x00},   // ! 0x21 33
            {0x00,0x07,0x00,0x07,0x00},   // " 0x22 34
            {0x14,0x7f,0x14,0x7f,0x14},   // # 0x23 35
            {0x00,0x07,0x04,0x1e,0x00},   // $ 0x24 36
            {0x23,0x13,0x08,0x64,0x62},   // % 0x25 37
            {0x36,0x49,0x56,0x20,0x50},   // & 0x26 38
            {0x00,0x00,0x07,0x00,0x00},   // ' 0x27 39
            {0x00,0x1c,0x22,0x41,0x00},   // ( 0x28 40
            {0x00,0x41,0x22,0x1c,0x00},   // ) 0x29 41
            {0x14,0x08,0x3e,0x08,0x14},   // * 0x2a 42
            {0x08,0x08,0x3e,0x08,0x08},   // + 0x2b 43
            {0x00,0x50,0x30,0x00,0x00},   // , 0x2c 44
            {0x08,0x08,0x08,0x08,0x08},   // - 0x2d 45
            {0x00,0x60,0x60,0x00,0x00},   // . 0x2e 46
            {0x20,0x10,0x08,0x04,0x02},   // / 0x2f 47
            {0x3e,0x51,0x49,0x45,0x3e},   // 0 0x30 48
            {0x00,0x42,0x7f,0x40,0x00},   // 1 0x31 49
            {0x42,0x61,0x51,0x49,0x46},   // 2 0x32 50
            {0x21,0x41,0x45,0x4b,0x31},   // 3 0x33 51
            {0x18,0x14,0x12,0x7f,0x10},   // 4 0x34 52
            {0x27,0x45,0x45,0x45,0x39},   // 5 0x35 53
            {0x3c,0x4a,0x49,0x49,0x30},   // 6 0x36 54
            {0x01,0x71,0x09,0x05,0x03},   // 7 0x37 55
            {0x36,0x49,0x49,0x49,0x36},   // 8 0x38 56
            {0x06,0x49,0x49,0x29,0x1e},   // 9 0x39 57
            {0x00,0x36,0x36,0x00,0x00},   // : 0x3a 58
            {0x00,0x56,0x36,0x00,0x00},   // ; 0x3b 59
            {0x08,0x14,0x22,0x41,0x00},   // < 0x3c 60
            {0x14,0x14,0x14,0x14,0x14},   // = 0x3d 61
            {0x00,0x41,0x22,0x14,0x08},   // > 0x3e 62
            {0x02,0x01,0x51,0x09,0x06},   // ? 0x3f 63
            {0x3e,0x41,0x5d,0x49,0x4e},   // @ 0x40 64
            {0x7e,0x09,0x09,0x09,0x7e},   // A 0x41 65
            {0x7f,0x49,0x49,0x49,0x36},   // B 0x42 66
            {0x3e,0x41,0x41,0x41,0x22},   // C 0x43 67
            {0x7f,0x41,0x41,0x41,0x3e},   // D 0x44 68
            {0x7f,0x49,0x49,0x49,0x41},   // E 0x45 69
            {0x7f,0x09,0x09,0x09,0x01},   // F 0x46 70
            {0x3e,0x41,0x49,0x49,0x7a},   // G 0x47 71
            {0x7f,0x08,0x08,0x08,0x7f},   // H 0x48 72
            {0x00,0x41,0x7f,0x41,0x00},   // I 0x49 73
            {0x20,0x40,0x41,0x3f,0x01},   // J 0x4a 74
            {0x7f,0x08,0x14,0x22,0x41},   // K 0x4b 75
            {0x7f,0x40,0x40,0x40,0x40},   // L 0x4c 76
            {0x7f,0x02,0x0c,0x02,0x7f},   // M 0x4d 77
            {0x7f,0x04,0x08,0x10,0x7f},   // N 0x4e 78
            {0x3e,0x41,0x41,0x41,0x3e},   // O 0x4f 79
            {0x7f,0x09,0x09,0x09,0x06},   // P 0x50 80
            {0x3e,0x41,0x51,0x21,0x5e},   // Q 0x51 81
            {0x7f,0x09,0x19,0x29,0x46},   // R 0x52 82
            {0x46,0x49,0x49,0x49,0x31},   // S 0x53 83
            {0x01,0x01,0x7f,0x01,0x01},   // T 0x54 84
            {0x3f,0x40,0x40,0x40,0x3f},   // U 0x55 85
            {0x0f,0x30,0x40,0x30,0x0f},   // V 0x56 86
            {0x3f,0x40,0x30,0x40,0x3f},   // W 0x57 87
            {0x63,0x14,0x08,0x14,0x63},   // X 0x58 88
            {0x07,0x08,0x70,0x08,0x07},   // Y 0x59 89
            {0x61,0x51,0x49,0x45,0x43},   // Z 0x5a 90
            {0x3c,0x4a,0x49,0x29,0x1e},   // [ 0x5b 91
            {0x02,0x04,0x08,0x10,0x20},   // \ 0x5c 92
            {0x00,0x41,0x7f,0x00,0x00},   // ] 0x5d 93
            {0x04,0x02,0x01,0x02,0x04},   // ^ 0x5e 94
            {0x40,0x40,0x40,0x40,0x40},   // _ 0x5f 95
            {0x00,0x00,0x03,0x04,0x00},   // ` 0x60 96
            {0x20,0x54,0x54,0x54,0x78},   // a 0x61 97
            {0x7f,0x48,0x44,0x44,0x38},   // b 0x62 98
            {0x38,0x44,0x44,0x44,0x20},   // c 0x63 99
            {0x38,0x44,0x44,0x48,0x7f},   // d 0x64 100
            {0x38,0x54,0x54,0x54,0x18},   // e 0x65 101
            {0x08,0x7e,0x09,0x01,0x02},   // f 0x66 102
            {0x0c,0x52,0x52,0x52,0x3e},   // g 0x67 103
            {0x7f,0x08,0x04,0x04,0x78},   // h 0x68 104
            {0x00,0x44,0x7d,0x40,0x00},   // i 0x69 105
            {0x20,0x40,0x44,0x3d,0x00},   // j 0x6a 106
            {0x00,0x7f,0x10,0x28,0x44},   // k 0x6b 107
            {0x00,0x41,0x7f,0x40,0x00},   // l 0x6c 108
            {0x7c,0x04,0x18,0x04,0x78},   // m 0x6d 109
            {0x7c,0x08,0x04,0x04,0x78},   // n 0x6e 110
            {0x38,0x44,0x44,0x44,0x38},   // o 0x6f 111
            {0x7c,0x14,0x14,0x14,0x08},   // p 0x70 112
            {0x08,0x14,0x14,0x18,0x7c},   // q 0x71 113
            {0x7c,0x08,0x04,0x04,0x08},   // r 0x72 114
            {0x48,0x54,0x54,0x54,0x20},   // s 0x73 115
            {0x04,0x3f,0x44,0x40,0x20},   // t 0x74 116
            {0x3c,0x40,0x40,0x20,0x7c},   // u 0x75 117
            {0x1c,0x20,0x40,0x20,0x1c},   // v 0x76 118
            {0x3c,0x40,0x30,0x40,0x3c},   // w 0x77 119
            {0x44,0x28,0x10,0x28,0x44},   // x 0x78 120
            {0x0c,0x50,0x50,0x50,0x3c},   // y 0x79 121
            {0x44,0x64,0x54,0x4c,0x44},   // z 0x7a 122
            {0x00,0x08,0x36,0x41,0x41},   // { 0x7b 123
            {0x00,0x00,0x7f,0x00,0x00},   // | 0x7c 124
            {0x41,0x41,0x36,0x08,0x00},   // } 0x7d 125
            {0x04,0x02,0x04,0x08,0x04},   // ~ 0x7e 126
      };

PS: The code was originally written for bikes, (I made one last last year)
and my project (as you can see in the video) is designed vertically. Globe Design.

 // sensor setup
 const int sensorPIN = 12;  // define the Arduino sensor pin
.
.
.
sensVal = analogRead(sensorPIN);  // read the Hall Effect Sensor

Why are you setting a digital pin (pin12) and trying to analogueRead from it?

why? is it wrong? ok ill change that to digitalread, but that wont solve my mirrored display, right sir? thanks for the reply.

Can someone transfer this topic to another board/thread? So that I can receive more replies? :frowning:

I know a way, it is re-coding the hex values of each characters in the font.h
but that would take a long time. I know it can be solved just by editing the sketch.

Which Board your are using .
What is out put of hall sensor??

You appear to have 2 for loops in the program. One picks the letter to be displayed from the texString array and the other picks a column from the selected letter. What happens if you reverse the direction of both for loops ?

AMPS-N:
Which Board your are using .
What is out put of hall sensor??

I am using a Gizduino Board another generic version of arduino, which has an UNO bootloader.
I switched to Reed Switch, it has a longer range I think. I changed the pin of the reedswitch to pin 14 and then use analogRead. Whenever the reed switch enters the magnetic field, the circuit lights up.

UKHeliBob:
You appear to have 2 for loops in the program. One picks the letter to be displayed from the texString array and the other picks a column from the selected letter. What happens if you reverse the direction of both for loops ?

for (int i=charWidth; i>=0; i--) {
     byte b = font[ch][i];
     // bit shift through the byte and output it to the pin
     for (int j=charHeight; j>=0; j--) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     

     }

----RANDOM CHARACTERs. I could see a 0 I think.

 for (int i=charWidth; i>=0; i--) {
     byte b = font[i][ch];
      
     // bit shift through the byte and output it to the pin
     for (int j=charHeight; j>=0; j--) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     
     }

—RANDOM DISPLAY. LIKE UNREADABLE OUTPUTS.

  for (int i=0; i<charWidth; i++) {
     byte b = font[ch][i];
     
     // bit shift through the byte and output it to the pin
     for (int j=0; j<charHeight; j++) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     }

—DISPLAYS RIGHT BUT DISPLAYS MIRRORED STRING AGAIN.

  for (int i=0; i<charWidth; i++) {
     byte b = font[i][ch];
 
     // bit shift through the byte and output it to the pin
     for (int j=0; j<charHeight; j++) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     }

—RANDOM DISPLAY. LIKE UNREADABLE OUTPUTS

I will try to switch the position of the first and last hex digits of each character in font.h

If it is analog pin why u are digital pin while coding,

https://docs.google.com/file/d/0BxdLxDCD6Hiddi1GbDVsdXZZYm8/edit

// sensor setup
 const int sensorPIN = 12;  // define the Arduino sensor pin
.
.
.
sensVal = analogRead(sensorPIN);  // read the Hall Effect Sensor

AMPS-N:
If it is analog pin why u are digital pin while coding,

https://docs.google.com/file/d/0BxdLxDCD6Hiddi1GbDVsdXZZYm8/edit

// sensor setup

const int sensorPIN = 12;  // define the Arduino sensor pin
.
.
.
sensVal = analogRead(sensorPIN);  // read the Hall Effect Sensor

my bad sir. I already transferred the sensor to pin 14 (analog) then use an analogRead();
but that won’t solve my problem.
right now, the display is not mirrored, I swapped the first and last hex digit of letter L and letter P and letter E inside the font.h
my last problem is this: the display is still reversed. I mean this:
ESUALPPA ← it should be APPLAUSE.
I wonder how to output that in reversed order. :frowning:

Original code

  for (int i=0; i<charWidth; i++) {

New code

for (int i=charWidth; i>=0; i--) {

The original code reads data from column 0 to charWidth - 1
The new code reads data from charWidth to 0 so causes data to be read from outside the character array

I already transferred the sensor to pin 14 (analog) then use an analogRead();

Wouldn't it be better to use pin 14 as a digital input, and do a digitalRead?
analogRead is slooow.

For your reference here i am attaching the Image of the pinout.
I could not able to see

I already transferred the sensor to pin 14 (analog) then use an analogRead();

You being mentioning here.
A0 -A7 are the Analog pins
While Writing Code you need to say

const int sensorPIN = A0 or 1;  // define the Arduino sensor pin
.
sensVal = analogRead(sensorPIN);  // read the Hall Effect Sensor  
or
sensVal = analogRead(A0); directly

Hi, have you tried reversing the direction of your motor , that way your scan will be in the other direction.
Swapping the leads to the motor around?

Tom...... :slight_smile:

AMPS-N:
For your reference here i am attaching the Image of the pinout.
I could not able to see

I already transferred the sensor to pin 14 (analog) then use an analogRead();

You being mentioning here.
A0 -A7 are the Analog pins
While Writing Code you need to say

const int sensorPIN = A0 or 1;  // define the Arduino sensor pin

.
sensVal = analogRead(sensorPIN);  // read the Hall Effect Sensor  
or
sensVal = analogRead(A0); directly

No, it would be much better to use digitalRead, for which you simply need to set the pinMode.

@AMPS-N Is tHere Something wrOng wIth Your shiFt-kEY?

TomGeorge:
Hi, have you tried reversing the direction of your motor , that way your scan will be in the other direction.
Swapping the leads to the motor around?

Tom… :slight_smile:

that wouldn’t be possible for now. Normally the motors I think rotates in a direction my motor does.
:slight_smile: Leds are already reverse in the video. hehe

AWOL:

I already transferred the sensor to pin 14 (analog) then use an analogRead();

Wouldn’t it be better to use pin 14 as a digital input, and do a digitalRead?
analogRead is slooow.

DONE SIR! THANKSSSSSSSSSSSSSSSSSSSSSS!

UKHeliBob:
Original code

  for (int i=0; i<charWidth; i++) {

New code

for (int i=charWidth; i>=0; i--) {

The original code reads data from column 0 to charWidth - 1
The new code reads data from charWidth to 0 so causes data to be read from outside the character array

DAMN! YOU’RE SO GOOD! :wink:
It works now! BUT… I have to use a certain function in C that reverses the arrangement of characters in an array.
THANK YOU SO MUCH!!! NOW I don’t have to rewrite the hex values of each chars in font.h
thank u thank u!!! :slight_smile:

If someone know how to scroll (marquee) the display, I would be glad to accept and do your instructions.

here is the final code:

 // defining the alphabet
 #include "font.h"
 
 // define the Arduino LED pins in use
 const int LEDpins[] = {
   6,5,4,3,2,1,0};
 
 // number of LEDs
  const int charHeight = sizeof(LEDpins);
  const int charWidth = 5;
 
 
 
 // sensor setup
 const int sensorPIN = 14;  // define the Arduino sensor pin

//  boolean sensorFlag = false;  // stores sensor state
  int sensVal;  // variable to store the value coming from the sensor
 
 
 
 void setup()
 {
   pinMode(13, OUTPUT);
    pinMode(0 , OUTPUT);
   pinMode(1, OUTPUT);
    pinMode(2, OUTPUT);
     pinMode(3, OUTPUT);
    pinMode(4, OUTPUT);
    pinMode(5, OUTPUT);
    pinMode(6, OUTPUT);
 
   
  //   Serial.begin(9600);
 }
 
 void reverse_string(char str[])
{
    char c;
    char *p, *q;

    p = str;
    if (!p)
        return;

    q = p + 1;
    if (*q == '\0')
        return;

    c = *p;
    reverse_string(q);

    while (*q != '\0') {
        *p = *q;
        p++;
        q++;
    }
    *p = c;

    return;
}
 
 void loop()
 {
   // turn on Led for a circle in middle and proof that arduino is powered
    digitalWrite(13, HIGH);   // set the LED on  
    char textString[] = "glenn POSADAS";
     reverse_string(textString);
   sensVal = digitalRead(sensorPIN);  // read the Hall Effect Sensor  
 
 
 
 //    Serial.println(sensVal);
// delay(500 );  
// had difficulty here
// since it is a switch hall switch probably shoiuld just do digital read

 if (sensVal ==0) {
   // printing every letter of the textString
   for (int k=0; k<sizeof(textString); k++){
     printLetter(textString[k]);
   }

 }
 }
 
 
 
 
 void printLetter(char ch)
 {
   // make sure the character is within the alphabet bounds (defined by the font.h file)
   // if it's not, make it a blank character
   
    
   
   if (ch < 32 || ch > 126){
     ch = 32;
   }
   // subtract the space character (converts the ASCII number to the font index number)
   ch -= 32;
   // step through each byte of the character array
  for (int i=charWidth; i>=0; i--) { 
     byte b = font[ch][i];
     
 
 
     // bit shift through the byte and output it to the pin
     for (int j=charHeight; j>=0; j--) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     
     }
     // space between columns
 
 delayMicroseconds(900);
   }
   //clear the LEDs
 digitalWrite(0 , LOW);   // set the LED on
digitalWrite(1 , LOW);   // set the LED on
digitalWrite(2 , LOW);   // set the LED on
digitalWrite(3 , LOW);   // set the LED on
digitalWrite(4 ,LOW);   // set the LED on
digitalWrite(5 , LOW);   // set the LED on
digitalWrite(6 , LOW);   // set the LED on
   
   // space between letters
   delayMicroseconds(2500);
 
 }

If someone know how to scroll (marquee) the display, I would be glad to accept and do your instructions.

   // printing every letter of the textString
   for (int k=0; k<sizeof(textString); k++){
     printLetter(textString[k]);
   }

This for loop sends each letter to the display in turn starting at the beginning each time. If the start position was moved along the string after a suitable delay then the text would appear to scroll. You would need to deal with the wrap around, of course.

glenn_boy13:

  void setup()

{
  pinMode(13, OUTPUT);
   pinMode(0 , OUTPUT);
  pinMode(1, OUTPUT);
   pinMode(2, OUTPUT);
    pinMode(3, OUTPUT);
   pinMode(4, OUTPUT);
   pinMode(5, OUTPUT);
   pinMode(6, OUTPUT);
 //   Serial.begin(9600);
}

Where's pinMode(14,INPUT);?
And I suggest that you don't use pins 0 and 1 as they are used by Serial.

Henry_Best:

glenn_boy13:

  void setup()

{
  pinMode(13, OUTPUT);
    pinMode(0 , OUTPUT);
  pinMode(1, OUTPUT);
    pinMode(2, OUTPUT);
    pinMode(3, OUTPUT);
    pinMode(4, OUTPUT);
    pinMode(5, OUTPUT);
    pinMode(6, OUTPUT);
  //  Serial.begin(9600);
}

Where’s pinMode(14,INPUT);?
And I suggest that you don’t use pins 0 and 1 as they are used by Serial.

HELLO SIR! Yes, the codes here is merely my scratch. I’ve got now my final design.
but…
(see below)

UKHeliBob:

If someone know how to scroll (marquee) the display, I would be glad to accept and do your instructions.

   // printing every letter of the textString

for (int k=0; k<sizeof(textString); k++){
    printLetter(textString[k]);
  }



This for loop sends each letter to the display in turn starting at the beginning each time. If the start position was moved along the string after a suitable delay then the text would appear to scroll. You would need to deal with the wrap around, of course.

hey sir! I tried manipulating, testing and testing 1000000000x, the charWidth in the program.
here are the findings:

  1. IF charwidth is = 5 and the text is = “DIANA” ---- result: VERY GOOD. Stable, not scrolling but still is the display.
  2. IF charwidth is = 20 and the text is = “SOFTWARE ENGINEER GLENN POSADAS” — result: So many characters that doesn’t form any name.
  3. If charwidth is = 5 and the text is = “longlongLonglong long GLENN” — result:I can see random characters from the text, it doesn’t scroll.

any suggestions?
ps: my sensor is fully functional. the leds will light only if and only if the sensor is in the magnetic field.
I’ve been testing the design since 12midnight, and it is 3:12AM now. XD

Ok. so the end in debugging this project is quite near.
I learned that charWidth is best to have a value of 5. that is constant smiley-grin As it was declared originally by the author of such codes in instructables. Yes, this project is modified by me. My project is a globe and the instructable is a fan.

Findings:

  1. if the text is: “DIANA ROSE smiley” — 13 characters or less than that( including white spaces), the result is super fine. super stable.
  2. if the text is longer than 13 characters, the display is still readable but not scrolling. ughhhhhhhhh
    say, my text is: “DIANA ROSE CUSTODIO smiley”. first it will display the “DIANA ROSE CUST” then the rest. 2 displays each second.

I know sir UKHeliBob is right, but I can’t implement what he is saying. smiley-sad

AWOL:
You can put it up wherever you like, but without seeing any code, I don’t see it’ll do you much good.

sorry sir. I forgot to include my most updated code.

// defining the alphabet
 #include "font.h"
 
 // define the Arduino LED pins in use
 const int LEDpins[] = {
   8,7,6,5,4,3,2};
 
 // number of LEDs
  const int charHeight = sizeof(LEDpins);
  const int charWidth = 5;
 
 
 
 // sensor setup
 const int sensorPIN = 12;  // define the Arduino sensor pin

//  boolean sensorFlag = false;  // stores sensor state
  int sensVal;  // variable to store the value coming from the sensor
 
 

 void setup()
 {
   pinMode(13, OUTPUT);

    pinMode(2, OUTPUT);
     pinMode(3, OUTPUT);
    pinMode(4, OUTPUT);
    pinMode(5, OUTPUT);
    pinMode(6, OUTPUT);
     pinMode(7 , OUTPUT);
   pinMode(8, OUTPUT);

   
     Serial.begin(9600);
 }
 
 void reverse_string(char str[])
{
    char c;
    char *p, *q;

    p = str;
    if (!p)
        return;

    q = p + 1;
    if (*q == '\0')
        return;

    c = *p;
    reverse_string(q);

    while (*q != '\0') {
        *p = *q;
        p++;
        q++;
    }
    *p = c;

    return;
}
 
 void loop()
 {
   
   //try random
   // turn on Led for a circle in middle and proof that arduino is powered
    digitalWrite(13, HIGH);   // set the LED on  
    char textString[] = "diana rose c posadas :)  ";
//     reverse_string(textString);
   sensVal = digitalRead(sensorPIN);  // read the Hall Effect Sensor  
 
    analogWrite(9, 0);
    
 
 //    Serial.println(sensVal);
// delay(500 );  
// had difficulty here
// since it is a switch hall switch probably shoiuld just do digital read

 if (sensVal == HIGH) {
   
   // printing every letter of the textString
   for (int k=0; k<sizeof(textString); k++){
     printLetter(textString[k]);
     delayMicroseconds(2000);
   }

 }
 }
 
 
 
 
 void printLetter(char ch)
 {
   // make sure the character is within the alphabet bounds (defined by the font.h file)
   // if it's not, make it a blank character
   
    
   
    if (ch < 32 || ch > 126){
     ch = 32;
   }
   // subtract the space character (converts the ASCII number to the font index number)
   ch -= 32;
   // step through each byte of the character array
  for (int i=0; i<charWidth; i++) {
     byte b = font[ch][i];
     
 
 
     // bit shift through the byte and output it to the pin
     for (int j=charHeight; j>=0; j--) {
       digitalWrite(LEDpins[j], !!(b & (1 << j)));
     
     }
     // space between columns
 
 delayMicroseconds(700);
   }
   //clear the LEDs

digitalWrite(2 , LOW);   // set the LED on
digitalWrite(3 , LOW);   // set the LED on
digitalWrite(4 ,LOW);   // set the LED on
digitalWrite(5 , LOW);   // set the LED on
digitalWrite(6 , LOW);   // set the LED on
    digitalWrite(7 , LOW);   // set the LED on
digitalWrite(8 , LOW);   // set the LED on
   // space between letters
   delayMicroseconds(700);
 
 }

so, I’ve changed the settings in void loop. Most of the makers of arduino POV in the internet use this:

if(sensorReading == LOW) 
{
then execute printing POV;
}

I’ve tried the sensorreading is equals to LOW . I’ve tried sensorreading is equals to HIGH as well. There are quite difference between that two. But I can’t achieve what I want: “SCROLLING TEXT”.

Also I’ve tried excluding the sensor reading, I thought it would work, but no. As I’ve said in the above, someone suggested an instruction but I can’t implement it.