Graph a single line from analog read in a TFT

PaulDLCMx · October 20, 2018, 3:57am

Hello, thanks for view my post.

I'm triyng to make a graph in a 3.5 TFT LCD SHIELD from an analog read and what I get is a bis section of the screen being filled with the line, but I need a single line, could be just a pixel of width.

The graph I try to see must be between 19 mm and 19 mm, just in the middle of the Y axis, actually I have solved this but the graph fills half of the screen and I can't get how to make just a line, just like when you open the Serial Plotter. I'm using a TFT that has the ILI9486/ILI9488 chip, and I made this run with the MCUFRIEND_kbv.h library. I attach the code and a picture of how my graph is.

#include <Adafruit_GFX.h> // Hardware-specific library
#include <MCUFRIEND_kbv.h>
#include <Time.h>
MCUFRIEND_kbv tft;

#define BLACK   0x0000
#define BLUE    0x001F
#define RED     0xF800
#define GREEN   0x07E0
#define CYAN    0x07FF
#define MAGENTA 0xF81F
#define YELLOW  0xFFE0
#define WHITE   0xFFFF

int xPos = 0;
int n=0;

int16_t ht = 16, top = 3, line, lines = 15, scroll;

void setup(){
  tft.reset();
    uint16_t id = tft.readID();
    tft.begin(id);
    tft.setRotation(1);
    tft.fillScreen(BLACK);
    tft.setTextColor(WHITE); 
     }

void loop(){
  float sensor = analogRead(A5);
  float volt=sensor*5/1024;
  //If chnages to map(sensor,0,1023....) it will fill all the pot ohm value
  float graphHeight = map(sensor,410,614,0,tft.height());
  tft.drawLine(xPos, tft.height() - graphHeight, xPos, tft.height(),WHITE);
  if (xPos >= 480) {
    xPos = 20;
    tft.fillScreen(BLACK);
    tft.setCursor(120,10);
    tft.print("Seismic Wave Sensor");
  tft.setTextSize(2);
  tft.setTextColor(WHITE);
   tft.setCursor(120,300);
  tft.print("INGENIERIA GEOFISICA");
  tft.drawLine(20,60,20,260,WHITE);
  tft.setTextSize(2);
  tft.setTextColor(WHITE);
  tft.setCursor(30,50);
  tft.print("19 mm");
  tft.setTextSize(2);
  tft.setTextColor(WHITE);
  tft.setCursor(30,260);
  tft.print("19 mm"); 
  } 
  else {
    xPos++;
      }
   delay(16);
}

I think my problem could be in the part of graphHeight or the tft.drawLine, but I have been using Arduino for short time, and I know you are experts in this. Please I really need help

DaveEvans · October 20, 2018, 4:44am

Just draw pixels at the appropriate points instead of lines.

PaulDLCMx · October 20, 2018, 5:06am

Do you mean that I should use the tft.drawPixel instead of tft.drawLine? I just did it,but I really don't realize how to modify this part:

float graphHeight = map(sensor,0,1023,0,tft.height());
tft.drawPixel(xPos, tft.height() - graphHeight, xPos, tft.height(),WHITE);

Of course, the library requires other parameters

DaveEvans · October 20, 2018, 5:43am

What parameters does the library require for drawPixel?

PaulRB · October 20, 2018, 7:18am

Try this (untested):

#include <Adafruit_GFX.h> // Hardware-specific library
#include <MCUFRIEND_kbv.h>
#include <Time.h>
MCUFRIEND_kbv tft;

#define BLACK   0x0000
#define BLUE    0x001F
#define RED     0xF800
#define GREEN   0x07E0
#define CYAN    0x07FF
#define MAGENTA 0xF81F
#define YELLOW  0xFFE0
#define WHITE   0xFFFF

int xPos = 20, xPosPrev = 20;
int n = 0;
int graphHeightPrev = 0

int16_t ht = 16, top = 3, line, lines = 15, scroll;

void setup() {
  tft.reset();
  uint16_t id = tft.readID();
  tft.begin(id);
  tft.setRotation(1);
  tft.fillScreen(BLACK);
  tft.setTextColor(WHITE);
}

void loop() {
  int sensor = analogRead(A5);
  //If chnages to map(sensor,0,1023....) it will fill all the pot ohm value
  int graphHeight = map(sensor, 410, 614, 0, tft.height());
  tft.drawLine(xPosPrev, tft.height() - graphHeightPrev, xPos, tft.height() - graphHeight, WHITE);
  graphHeightPrev = graphHeight;
  if (xPos >= 480) {
    xPos = 20;
    xPosPrev = 20;
    tft.fillScreen(BLACK);
    tft.setCursor(120, 10);
    tft.print("Seismic Wave Sensor");
    tft.setTextSize(2);
    tft.setTextColor(WHITE);
    tft.setCursor(120, 300);
    tft.print("INGENIERIA GEOFISICA");
    tft.drawLine(20, 60, 20, 260, WHITE);
    tft.setTextSize(2);
    tft.setTextColor(WHITE);
    tft.setCursor(30, 50);
    tft.print("19 mm");
    tft.setTextSize(2);
    tft.setTextColor(WHITE);
    tft.setCursor(30, 260);
    tft.print("19 mm");
  }
  else {
    xPosPrev = xPos;
    xPos++;
  }
  delay(16);
}

PaulDLCMx · October 20, 2018, 2:22pm

DaveEvans:
What parameters does the library require for drawPixel?

It requires: no matching function for call to 'MCUFRIEND_kbv::drawPixel(int&, float, int&, int16_t, unsigned int)'

system · October 20, 2018, 2:39pm

no matching function for call to 'MCUFRIEND_kbv::drawPixel(int&, float, int&, int16_t, unsigned int)'

So, lose the float.

PaulRB · October 20, 2018, 4:04pm

AWOL:
So, lose the float.

I'm not sure that's the problem. The code in the OP compiled ok, and I would not expect drawLine() to accept a float and drawPixel() not accept a float, so I think an implicit conversion to int must have been going on.

I think it's the number of parameters that is the problem. drawPixel() expects 2 fewer parameters than drawLine() I would imagine.

@Paul did you try my code from post #4?

@AWOL I removed the uneccessary use of float in my suggested code changes.

PaulDLCMx · October 20, 2018, 5:40pm

YES PaulRB!!! It really works!
Thank you so much!! and sorry for takin a lot of time to answer!!

So for that, the last code is the one you gave me!

PaulRB · October 20, 2018, 6:02pm

Thank me by working out for yourself what changes I made and, for any that you don't understand, asking me why, and then taking the time to understand them yourself

shankarsm1522 · May 22, 2019, 6:28am

i have used this code mr.paul rb but i have not received the single analog graph
can you please guide me to get the output as u get.

#include <Adafruit_GFX.h> // Hardware-specific library
#include <MCUFRIEND_kbv.h>
#include <Time.h>
MCUFRIEND_kbv tft;

#define BLACK 0x0000
#define BLUE 0x001F
#define RED 0xF800
#define GREEN 0x07E0
#define CYAN 0x07FF
#define MAGENTA 0xF81F
#define YELLOW 0xFFE0
#define WHITE 0xFFFF

int xPos = 20, xPosPrev = 20;
int n = 0;
int graphHeightPrev = 0

int16_t ht = 16, top = 3, line, lines = 15, scroll;

void setup() {
tft.reset();
uint16_t id = tft.readID();
tft.begin(id);
tft.setRotation(1);
tft.fillScreen(BLACK);
tft.setTextColor(WHITE);
}

void loop() {
int sensor = analogRead(A5);
//If chnages to map(sensor,0,1023....) it will fill all the pot ohm value
int graphHeight = map(sensor, 410, 614, 0, tft.height());
tft.drawLine(xPosPrev, tft.height() - graphHeightPrev, xPos, tft.height() - graphHeight, WHITE);
graphHeightPrev = graphHeight;
if (xPos >= 480) {
xPos = 20;
xPosPrev = 20;
tft.fillScreen(BLACK);
tft.setCursor(120, 10);
tft.print("Seismic Wave Sensor");
tft.setTextSize(2);
tft.setTextColor(WHITE);
tft.setCursor(120, 300);
tft.print("INGENIERIA GEOFISICA");
tft.drawLine(20, 60, 20, 260, WHITE);
tft.setTextSize(2);
tft.setTextColor(WHITE);
tft.setCursor(30, 50);
tft.print("19 mm");
tft.setTextSize(2);
tft.setTextColor(WHITE);
tft.setCursor(30, 260);
tft.print("19 mm");
}
else {
xPosPrev = xPos;
xPos++;
}
delay(16);
}

shankarsm1522 · May 22, 2019, 6:33am

PaulRB:

Captura2.JPG795×485 40.3 KB

Thank me by working out for yourself what changes I made and, for any that you don't understand, asking me why, and then taking the time to understand them yourself

can you please help me out this problem

PaulRB · May 22, 2019, 1:12pm

Please do not post code without using code tags. Modify your post above and correct it.

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Graph a single line from analog read in a TFT

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