Welcome to Pete Brown's 10rem.net

First time here? If you are a developer or are interested in Microsoft tools and technology, please consider subscribing to the latest posts.

You may also be interested in my blog archives, the articles section, or some of my lab projects such as the C64 emulator written in Silverlight.

(hide this)

Using a 4x20 HD44780-controlled LCD Display with the Netduino

Pete Brown - 24 September 2010

Not too long ago, I got my hands on a Netduino (an Arduino-compatible board you program using the .NET Micro Framework and Visual Studio 2010), and did the obligatory BlinkenLight application. Afterwards, Scott way one-upped me and built an awesome morse code app. The stakes were getting higher, so I had to do something that seemed cooler than morse code. Hard to top, I know. I bet Hello World would do it! ;)

So, I purchased an LCD through Hacktronics, via Amazon. The LCD is no longer listed as available, but Hacktronics has other LCDs you can order through their site. The LCD comes with a set of pin headers as well as a resistor for the backlight LED. You need to solder the headers on yourself. The board is covered in solder resist, so this isn't actually very difficult.

To use this LCD, which is controlled by a HD44780 LCD Controller, you'll need to either roll your own LCD library, or use this awesome library on codeplex. You can imagine which one I prefer. There are no official releases for that library, so you'll want to just download the source and add it to your project.

The CodePlex project provides the LCD class, and the GPIO 4 and 8 bit implementations. There's also an implementation using a shift register to cut down on pin count, but I'm not there yet.

Wiring the LCD to the Netduino

I found a number of wiring approaches online, but they differed in significant ways (more than just data pin assignments). The one that is closest to what I used is this table here (I really owe these guys for this post, as that is what finally made it gel for me). The actual pin assignments are as follows:

LCD Pin Number Symbol Netduino Pin Description
1 VSS GND Ground
2 VDD 5V Logic voltage
3 V0 10K Pot Leg 2 op voltage for LCD. Controls color/contrast
4 RS D12 Register selector
5 R/W GND Low means write, so you can just ground it
6 E D11 Chip enable
7 DB0 D9 Data Bit 0
8 DB1 D8 Data Bit 1
9 DB2 D7 Data Bit 2
10 DB3 D6 Data Bit 3
11 DB4 D5 Data Bit 4
12 DB5 D4 Data Bit 5
13 DB6 D3 Data Bit 6
14 DB7 D2 Data Bit 7
15 LED(+) Resistor to 5V Backlight LED Anode
16 LED(-) Ground Backlight LED Cathode

I had a hard time with some initial wiring diagrams (ones that completely left out the backlight ??). I initially suspected my soldering, but luckily I have a brand spanking new BK Precision 2709B with a continuity meter.


I checked each of the solder pads against the pins and found they were all fine. In the end, it was just that the backlight was left out of other diagrams, or wired to a pin that isn't inherently supported by the Netduino LCD library (presumably I could have just set that pin high to turn on the backlight. I'll try that later). Here's the whole wiring mess:


Look, I even have an Apple on my desk ;) Seriously, the wiring is a mess. I found myself wishing I had more than just a few colors of jumper wires. Nevertheless, it works. (Yes, it's upside down because my USB cable is very short and stiff. I need to get a better micro USB cable)

Testing with Hello World

I tried to use the sample applications included in the codeplex project, but I got a really obscure error with the debugger, and was unable to deploy. It may have to do with mismatched versions of something, but I didn't have time tonight to dig in deeper.

So, what we'll do is copy the relevant code to our own new Netduino project. Once I did that, and modified the LCD constructor call to reflect the pins I used, all was good. Here's the code:

public static void Main()
    var lcdProvider = new GpioLcdTransferProvider(
        Pins.GPIO_PIN_D12,  // RS
        Pins.GPIO_NONE,     // RW
        Pins.GPIO_PIN_D11,  // enable
        Pins.GPIO_PIN_D9,   // d0
        Pins.GPIO_PIN_D8,   // d1
        Pins.GPIO_PIN_D7,   // d2
        Pins.GPIO_PIN_D6,   // d3
        Pins.GPIO_PIN_D5,   // d4
        Pins.GPIO_PIN_D4,   // d5
        Pins.GPIO_PIN_D3,   // d6
        Pins.GPIO_PIN_D2);  // d7

    // create the LCD interface
    var lcd = new Lcd(lcdProvider);

    // set up the number of columns and rows: 
    lcd.Begin(16, 4);

    // Print a message to the LCD.
    lcd.Write("hello, world!");

    while (true)
        // set the cursor to column 0, line 1
        lcd.SetCursorPosition(0, 1);

        // print the number of seconds since reset:
        lcd.Write((Utility.GetMachineTime().Ticks / 10000).ToString());


The example here prints "hello world!" on the first line, and the machine tick count on the second line, updated every 100ms (1/10 of a second). Here's a photo of the LCD running:


You can adjust the text color slightly by using the 10k pot. However, it has a very limited range.

You can find information on the supported character set for the HD44780 here. Apparently, you can also create your own characters sets.

So, that's it. I can't really explain in a blog post just how gratifying it is to write microcontroller code in .NET, and see results in something that is not being driven by a regular old computer. Seriously, it's super cool.

Source code is included below.


Source Code and Related Media

Download /media/67884/testlcdnetduino.zip
posted by Pete Brown on Friday, September 24, 2010
filed under:            

18 comments for “Using a 4x20 HD44780-controlled LCD Display with the Netduino”

  1. Szymonsays:
    Hi Pete,
    I'm glad that you found my LCD library useful. It's still not 100% complete thus no releases on CodePlex yet. Let me know if you have any suggestions on how I can improve it.

    Btw. You are right about the backlight pin. I forgot to implement this in the GPIO provider. I will fix this soon. But another option is to connect it to one of the PWM pins on Netduino so that you can control LCD brightness from code too.

  2. Mattiep321says:

    Thanks for the tutorial, and I'm up and running thanks to your help. I have a question about using a thermocouple with the max6675 amplifier with the above code, but I can't find any resource for the max6675 library on Netduino. Do you have a temp sensor that you have used with the N+?

  3. Bryan Dunlapsays:
    I have a few questions. I'm new at this... very new. I've followed your diagram as best as I could but I think I have something wrong. I've wired the LCD as you show above but with a couple of minor exceptions. I do not have a potentiometer so PIN 3 is wired nowhere. Also, I do not seem to be able to get my resistor to work that came with the LCD so I wired pin 15 directly to the 5V pin.

    The results seem to be that the LCD lights up but nothing prints on the screen when I run the App. Is it a necessity to have a potentiometer? I assumed it wasn't because there isn't one in any of the arduino examples but as I said, I'm very new to this. Any recommendations?
  4. Petesays:

    It has been a while since I wrote this, but the potentiometer was to set the operating voltage. You had to tweak that to get characters to display. Once you found the right setting, you could either leave it there, or replace it with an equivalent resistor. It's required to make the display work as I recall.

    Turn this off and go get a resistor so you don't burn out the backlight LED. That resister to 5V is to control the brightness of the backlight and make sure you don't burn it out.

  5. Yak52says:
    If you want to use this library with a 4x16 LCD you must change the third and the fourth elements of RowOffsets to 0x10 and 0x50. We define size of display in Begin method but not used defined parameters for caluclated address. Instead we using RowOffsets array. The same error is in the original Arduino library.
  6. Jeffsays:

    This is good stuff.

    I bought this LCD:

    I was currious if it was the same as what you were using. For some reason last night I connected everything the way you showed above but I am not getting anything to display.

    I also bought a backpack from adafruit, this one:

    I was able to get the dispay to work under I2C mode but not under SPI.

    Any idea?

    Thank you,
  7. Tomsays:
    So, I've tried wiring this up exactly as specified. I have a 20x4 and it shows a row of 20 blocks on row 1 and row 3. I am not seeing any text. I've tried setting this up a few different ways and it always shows like this. The backlight and text colors are nice, I know I have that (hooked up to a pot, so I know it's good). I have no idea why I'm not getting no next, I hope you do.
  8. Jan Vojtech Vaniceksays:
    thanks for this article!

    Im trying to get it working with 16x4 display WINSTAR WH1604E-NYG-JW with RW1067 controller chip. Im using 4-bit parallel communication and my result is like something adds one pixel before each character. Do you face such that behavior?

    Please see the photo of appereance:


Comment on this Post

Remember me