I am trying to get an Arduino LCD screen to display some text. However, despite the wiring being done correctly, the LCD display doesn't even turn on when I upload the code, let alone display text. I have also tried connecting a potentiometer that would allow me to change brightness / contrast, but to no avail.
The compiler shows no issues and the code is uploaded successfuly:
#include <LiquidCrystal.h>
LiquidCrystal screen(12 , 11 , 10 , 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2);
void setup() {
// put your setup code here, to run once:
screen.begin(16 , 2);
screen.setCursor(0 , 0);
screen.print("Hello world!");
screen.setCursor(0 , 1);
screen.print("Test successful!");
}
void loop() {
// put your main code here, to run repeatedly:
}
Am I missing something?
LiquidCrystal screen(12 , 11 , 10 , 9 , 8 , 7 , 6 , 5 , 4 , 3 , 2);
The LCD 16x2 are often setup to operate at 4-bit mode to save the number of GPIO pins required for interfacing with the LCD. For some reason, you seems to want to use 8-bit mode and choose to explicitly set the mode by your class instantiation. In this case, the function prototype according to the library source code would be:
void LiquidCrystal::init(uint8_t fourbitmode, uint8_t rs, uint8_t rw, uint8_t enable,
uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3,
uint8_t d4, uint8_t d5, uint8_t d6, uint8_t d7)
Noticed that the first argument in the class instantiation specify whether you'd want to setup the display to operate at 4-bit mode or 8-bit mode, so if you want to use the 8-bit mode, the instantiation should be:
LiquidCrystal screen(1, rs_pin, rw_pin, enable, d0, d1, d2, d3, d4, d5, d6, d7);
If you want to use the 4-bit mode, there is an class overload construct which only requires you to specify 6-pin with
LiquidCrystal screen(rs, enable, d0, d1, d2, d3)
It will internally set the fourbitmode to 0, and d4-d7 to 0.
Related
I have a set of leds that are setup every other led reversed so when I apply power one way light 1,3,5... light. Change power and 2,4,6... I'm trying to set the brightness using PWM on the digital pins. Here's my code:
unsigned long flashCount = 0;
bool bSwitch = true;
void setup()
{
pinMode(6, OUTPUT);
pinMode(7, OUTPUT);
}
void loop()
{
if((flashCount + 1000) < millis())
{
if(bSwitch)
{
analogWrite(6, 0);
analogWrite(7, 1);
bSwitch = false;
}
else
{
analogWrite(7, 0);
analogWrite(6, 1);
bSwitch = true;
}
flashCount = millis();
}
}
If I change analogWrite to 255 instead of 1, it will switch both sets of leds. If I change analogWrite to 127 or less, only one set will light. If I switch the led wires to the pins, the problem switches to the other set of lights.
The leds are like so:
GPIO pin 6 --------.-LED+.---.-LED+.---.-LED+.---.-LED+.---|
GPIO pin 7 ---.+LED-.---.+LED-.---.+LED-.---.+LED-.--------|
Change the connection of the LEDs to pins that both support PWM.
Not all pins support PWM. The analogWrite documentation specifies which pins depending on which board:
On most Arduino boards (those with the ATmega168 or ATmega328P), this function works on pins 3, 5, 6, 9, 10, and 11. On the Arduino Mega, it works on pins 2 - 13 and 44 - 46. Older Arduino boards with an ATmega8 only support analogWrite() on pins 9, 10, and 11.
The other factor is that analogWrite(255) and analogWrite(0) will revert to driving the output as a digital output. So writing 255 causes both pins to output (one as a digital output and the other in PWM mode). But writing 1 to 127 only causes the PWM capable pin to change.
From arduino's manpages:
Syntax
analogWrite(pin, value)
Parameters
pin: the pin to write to. Allowed data types: int.
value: the duty cycle: between 0 (always off) and 255 (always on). Allowed data types: int
Using an analogWrite with a value of 1 is essentially near-zero. 255 would be full voltage. You're attempting to use analogWrite() as if it was digitalWrite().
Consider using digital write instead in your code: https://www.arduino.cc/reference/en/language/functions/digital-io/digitalwrite/
As for your LED's behavior, it seems like your circuit needs to be debugged as well: Your circuit will only allow current to flow when pin 7 is on. Diodes (Light Emitting Diodes) only allow current in one direction. If you're intending to have the LED's alternate, they should all be oriented with the positives pointing toward their GPIO pin and where they meet they should be grounded with a pull-down resistor.
I am learning Arduino and I was making one program which will print "Hello" to the lcd display connected to arduino.
I dont know what is wrong but the LCD is not showing desired output, rather shows special characters and when I increase/decrease the contrast of lcd using the Potentiometer, the characters changes everytime.
my code is:
// include the library code:
#include <LiquidCrystal.h>
// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 12, en = 11, d4 = 5, d5 = 4, d6 = 3, d7 = 2;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
void setup() {
// set up the LCD's number of columns and rows:
lcd.begin(16, 2);
// Print a message to the LCD.
lcd.print("hello");
}
void loop() {
// set the cursor to column 0, line 1
// (note: line 1 is the second row, since counting begins with 0):
lcd.setCursor(0, 1);
// print the number of seconds since reset:
lcd.print(millis() / 1000);
}
Please help.
Check what kind of lcd you are using.
Some lcd's come with the pin numbering reversed. IE the location of the 16 pins is on the top left corner, but instead of starting with pin number 1, the lcd starts with pin number 16.
Since the format of the LCD pins is the same both way (GND, VCC, input * 14, vcc, Gnd) it does not cause shorting problems, But the control signals are sent to the data pins, and the data signals are sent to the control pins.
I got this hint from the fact that changing the brightness changes the characters. If I am right, changing the contrast via the potentiometer will do you no good with respect to the actual contrast.
I am using an Arduino board to read out the value of a soft potmeter. (a strip that detects touch). This works perfectly fine as long as the strip is being touched (a resistance is added to the current).
When the strip is not touched, a completely random floating number is read by the analog pin. Forums mention that you have to add a pullup/pulldown resistor to cancel this effect, but this does not seem te be working. What is wrong with this code?
int potPin = 2;
int curval = 0;
// detect potmeter value
void setup() {
//enable pullup resistor, but still results in erratic output
//when potmeter is not touched
digitalWrite(potPin, HIGH);
//write to serial
Serial.begin(9600);
}
void loop() {
curval = analogRead(potPin);
// this works when the potmeter is being pressed (displays 0 to 1024)
Serial.println(curval);
delay(150);
}
Change
int potPin = 2;
to
int potPin = A2;
Your original use of "2" in both places is assigning Digital Pin 2 to pull-up and reading from Analog Channel 2. As "2" maps correspondingly to is PortD bit 2 and Analog Channel 2 (aka ADC2) is PortC bit 2. As shown below
digitalWrite(2, HIGH); // Pin D2
curval = analogRead(2); // AMUX Channel 2
where A2 shown below is interpreted as follows
digitalWrite(A2, HIGH); // Pin (A2 aka D16)
curval = analogRead(A2); // AMUX Channel 2 on Pin A2
On an UNO (ATmega328) the analogRead() function will interpret 0-7 as channels and will convert the pins A0 through A7 (D14-D21) to corresponding channels, to read from.
Note:
ADC6 and 7 are not available on the chip used on the UNO.
A0-A7 are alias for Digital 14 through 21. Where the labels A0-A7 are typically used.
So my problem is as title says: Arduino UNO analogRead always returns 1023.
But when I burn the same sketch in Arduino Mega 2650 everything works like a charm.
I have tried to change Atmel chips on the UNO, have tried like 3 of them (ATMEGA328P-PU) and nothing changes.
I'm trying to count signals from a hall effect sensor and display the count on a 7 segment display.
Here is the code:
#include "SevSeg.h"
SevSeg sevseg;
volatile int rpmcount;
void setup() {
Serial.begin(9600);
pinMode(2,INPUT_PULLUP);
rpmcount = 0;
sevseg.Begin(1,3,4,5,6,7,8,9,10,11,12,13);
}
int border=15;
void loop() {
int tmp=0;
tmp = analogRead(0);
if(!digitalRead(2))rpmcount=0;
Serial.println(tmp,DEC);
if(tmp<=border && res >border){
rpmcount++;
if(rpmcount>9999)rpmcount=0;
}
res=tmp;
sevseg.NewNum(rpmcount,(byte) 0);
sevseg.PrintOutput();
}
Any help would be much appreciated
This sounds to me as if you had the internal pullup resistor on the ADC pin enabled.
generic checklist:
ACD bit in ACSR is 0 (comparator enable)
MUX bits in ADMUX set properly
correct AREF selected
ADC pin set as input
internal pull up resistors are deselected
I am in between a small project using Arduino Uno R3 where i have to control a 9 X 16 LED Matrix.
Before i started the project i had planned for 8 X 8 LED Matrix (solution here would work for 8X8) and i know the same solution will work if I use a Arduino Mega (with more output pins)
Can any one suggest me how to control a 9 * 16 LED Matrix with Arduino UNO
You can drive up to 512 LEDs with some MAX7221 LED driver chips.
See here for instructions.
Another route to take would be to use multiplexers. They allow you to address many outputs (or inputs) with few arduino pins.
A setup similar to the one on the left would allow nesting of multiplexers to enable control of more LEDs. The only issue you would run into is that the LEDs may dim a little bit between being addressed.
Here's an Arduino page on the topic (with sample code). http://www.arduino.cc/playground/Learning/4051
/*
* codeexample for useing a 4051 * analog multiplexer / demultiplexer
* by david c. and tomek n.* for k3 / malm� h�gskola
*
* edited by Ross R.
*/
int r0 = 0; //value of select pin at the 4051 (s0)
int r1 = 0; //value of select pin at the 4051 (s1)
int r2 = 0; //value of select pin at the 4051 (s2)
int count = 0; //which y pin we are selecting
void setup(){
pinMode(2, OUTPUT); // s0
pinMode(3, OUTPUT); // s1
pinMode(4, OUTPUT); // s2
}
void loop () {
for (count=0; count<=7; count++) {
// select the bit
r0 = bitRead(count,0); // use this with arduino 0013 (and newer versions)
r1 = bitRead(count,1); // use this with arduino 0013 (and newer versions)
r2 = bitRead(count,2); // use this with arduino 0013 (and newer versions)
//r0 = count & 0x01; // old version of setting the bits
//r1 = (count>>1) & 0x01; // old version of setting the bits
//r2 = (count>>2) & 0x01; // old version of setting the bits
digitalWrite(2, r0);
digitalWrite(3, r1);
digitalWrite(4, r2);
//Either read or write the multiplexed pin here
}
}
Take a look at something like this: http://www.arduino.cc/playground/Learning/4051