These things come in a variety of shapes sizes and colors, and are great for displaying data such as readings or debugging information in this video I’m, going to show you how these LCDs work and how to control them with an Arduino also I’m, going to go through. How to access all of the features of the device through the Arduino liquid, crystal library and well you’ll, be surprised with what you can do. The first thing I’m going to talk about is the pin out of an LCD. The LCD has 16 pins as follows: let’s zoom, in to take a closer look, I’ll start with the basics, pin 1 or VSS is just ground. Pin 2 or VDD is 5 volts supply. The vio pin is the output from a potentiometer wiper pin to adjust contrast, pin 4 is called RS, it stands for register select, and this pin lets you choose between sending commands or sending characters to the LCD. I’Ll. Give you an example here. A command would be something like set the cursor to a certain position or clear the display, or even turn off the display. A character is just a text symbol that you want to display. When the RS pin is given zero, volts or ground, you send it a command, and when you give it 5 volts, you send data such as a character: I’m printing text, clearing the display printing, more text, setting the cursor printing, some symbols, setting the cursor somewhere else.
Printing, more text and clearing the display after the RS pin comes the art, W pin. This stands for readwrite and it lets you select between giving an instruction to the LCD like clearing the screen or sending data and reading information from the LCD. What information is there to read from the LCD you may ask? Well, the answer is actually not much. One instance of this that I can think of is to check for something known as a busy flag. Basically, when the LCD is processing information and executing its instructions, it will make pin d7 go high to indicate that it’s in the middle of doing something, when it’s free and ready to accept new instructions. That pin will go low. However, you can’t check this unless the LCDs in read mode, and for that you will need to the rwn go hi. However, the Arduino liquid crystal library is quite clever in the way it handles things. You can tie the RW pin straight to ground which permanently puts the LCD in right mode and introduces a long enough delay for the LCD to become free. This is less efficient code, but it saves on a pressures I open and you wouldn’t notice. The extra time taken anyway, then comes the e or enable pin. You can think of this as sort of a light switch for the LCD. When you flash this, pin high and then low again, the LCD can see the state of the other pins and execute the right command.
Next you’ll see pins d0 all the way through to d7. This is an 8 bit parallel data port for the LCD. After setting the RS and rw pins, you would make this port equal the 8 bit value of the character or command that you want to send. For example, the value for the capital letter a is in binary, zero one, zero, zero, zero, zero, zero 1 and the 8 bit value for the command. Clear screen is just zero: zero, zero, zero, zero, zero, zero one to check the values of commands refer to the data sheet, I’ve put a link to download it in the description to check the values of characters and symbols. Just Google, the American Standard Code for information, interchange or ASCII. Finally, the last two pins are the anode and cathode for the LED backlight I’m, going to give you a quick example of what goes on when you tell the LCD to do something. You don’t really need to memorize this, because the liquid crystal library takes care of most of it. For you say I want to display the capital letter a first hour check. If the LCD is busy to do this, I would go in to read mode, so my RW pin would be high and keep flashing. The enable pin until the busy flag goes low. The busy flag is located on pin d7 when it goes low. I know that the LCD is ready to accept instructions.
The first thing I might want to do is clear. The display the binary code for this command is zero. Zero: zero, zero, zero, zero zero one. If you remember to send the command the RS pin, must be low and to write to the LCD the RW pin has to be low as well. Then I would make the parallel data port on the LCD equal, the binary. I want to send remember: d7 is the most significant or rightmost bit and d0 is the least significant or leftmost bit. This is the reverse order of how the pins are arranged on the LCD. So, anyway, I’ll write the binary code: zero, zero, zero, zero, zero, zero, zero one to the LCD port. Finally, I would have to flash DNA we’ll play an on the LCD like flashing a light, so the LCD can sort of see the data on the data port. Also, I would put a small delay after sending the command, because it takes a little bit of time for the LCD to execute its commands. You can find the exact times on the hd44780 datasheet, but for clearing the screen. A delay of around 2 milliseconds is fine. Now that I’ve cleared the screen, I need to print the letter A first. I need to wait until the LCD is no longer busy. Now that it’s free, I can send the letter A to the LCD doing. This is very similar to sending a command only when sending data the RS pin, which is the register, select, pin, needs to be high and the read, write or RW pin would remain low.
Then I would send the ASCII the ASC III data code for a capital, A which happens to be in binary zero one: zero, zero, zero, zero, zero one, two, the data port then just like, when sending a command, I would flash the enable pin for the LCD To see the data, the circuit that we’re going to use is as follows: the RS pin is connected to pin 12 of the Arduino, and the enable pin is connected to pin 11. The RW pin is connected straight to ground and pins default. D7 are connected to the Arduino pins 5 to 2. You notice that I haven’t connected pins D 2 to D 0 to anything. This is because we’re going to operate the LCD in something called 4 bit mode. This is when, instead of sending the 8 bit character command value in one go, we send it in to half bytes or nibbles in a row. This just saves an io pins. Also, the potentiometer is about 10 kilo ohms and it adjusts the contrast of the display like this. So the first thing we’re going to want to do is import the liquid crystal library. You just go to sketch and import library and just quickly look at crystal then we’re going to create our LCD object and name it. Something like just LCD and type in the RS pin the e pin d4 d5, d6 and d7. Then we’re just going to go to our setup section and initialize, the LCD by typing in LCD dot begin and the number of columns by the number of rows.
So we’re, using a sixteen by two and we’re, going to clear the LCD just in case there’s something already printed. This is not really necessary, but it’s a good habit to get into and then we’re just going to go to a loop and let’s try printing something. So we just do LCD dot print and enclose whatever you want to print in double quotation. Marks like that and we’ll add some delays, so we’ll cycle through a bunch of things, so you can actually see what’s happening and now we’re gon na try and set the cursor so we’re going to clear the LCD and use the set cursor command and you type In the row by the column indexing from zero, then we’re just going to go LCD, dot, print and type in something like setting cursor and we’re gon na add another delay and do something else after that. So let’s do that now I’ll CD to clear again just to get rid of whatever’s on the screen and let’s um let’s put in a and a blinking cursor. So we type in something and this command is called LCD. Blink and it’s. Pretty simple there’s got a small delay again and let’s get rid of the blinking cursor and create an underline cursor, so LCD print underline cursor or Uline cursor, and all we actually forgot to enclose that within double quotation, marks and LCD dot. Cursor is the command to create an underline, cursor and we’ll, add a small delay and then we’re going to get rid of the cursor by typing LCD to clear and this command is called LCD, no cursor and will print the text first and then type in LCD.
No cursor with a C capital and that should get rid of the cursor that’s there and add a small delay by the way. If you want to get rid of the blinking cursor you just type in LCD, no blink, you can clear it again and that’s some. I don’t know let’s turn off the display, so we’ll type in no display and we’ll add a small delay in there as well. Just so you can actually see the text and then we’ll turn it off. So maybe it delay up. I don’t know one second and we’re just going to go LCD, no display D capital that’s the simple command to turn off the display. Remember the text is still there. You just turned off the display, so we’re going to actually print LCD display on so and then we’re going to turn on the display. So we’ll create a small delay, so you can see the display being off and then we’re going to turn on the display and the text is magically going to be changed because even though it displays off the LCD is still working and we’re going to add a Small delay and repeat the loop all over again and just some bug’s we need to fix. We need to type in LCD, no blink before doing the LCD dot print or before doing the LCD to cursor command. Otherwise, we’ll have two types of crushes going on at the same time, and we forgot to clear the display here as well before typing in the display on.
We need to clear the display and then type in display on jazzing t is doing exactly as you expected. Setting the cursor printing display putting a blinky cursor and an underline cursor, and you should turn off the cursor after that. Yep then turn off the display and we actually forgot a clear to display one last time before starting the loop again so you’ll see what that looks like yeah like that, if you think each character on the LCD is a block of pixels rather than a unique Symbol then it’s easy to see how the characters are formed. Each block is 5 pixels by 8 pixels, but the bottom row is usually left blank to leave room for a cursor LCD is like these. With the industry. Standard Hitachi controller inside can support up to 8 different custom characters. So the first thing we’re going to need to do is create an array of bytes and since it LCD has 5 pixels by 7 pixels, the bytes are going to be 5 pixels long and they’re going to be 7 of them. I’Ve just created enough space for an extra one, just in case so 5 pixels and I’m, sending them all to 0 right now. But if you turn them to 1, then that pixel would turn on on the LCD. So it should be just one: mori and we’ve got the commas as well between each between each byte next thing, we’re going to have to do is use a command called LCD, create car, and that should be, or actually we forgot to rename the before name the Bytes so let’s call it something like custom car anyway, so we’re going to use LCD to create car C capital, 2nd C and we’re going to create a car character which has a number in the memory address.
So we’ll put it as 0 and use the byte array of custom, car and let’s print some text just to say what we’re doing and then you have to use a command called LCD right and let’s set the cursor first actually to the second row. So 0, 1 and then we’re going to use LCD right 0 and that’s just the memory location in which that character, the custom character is stored and let’s, try compiling it and see if we get any errors and oh you’ll notice that we get this weird error. I don’t actually know what it means, but I found it goes away when you change the 0 to 1, for whatever reason I’ll try and look into it and let you know if actually find out what’s causing it, but that should be all and let’s compile. This takes a while on my computer, but let’s hold on and it seems to be working fine. There we go and that’s really all there is to creating custom characters, just remember to change the zeros to ones where you want a pixel to be displayed so that’s.
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Originally posted 2016-08-21 10:45:06.