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Using the Digital Discovery to debug a Character LCD

alexwonglik1

Digilent Digital Discovery is a combined logic analyzer and pattern generator instrument and allows you to debug, visualize,

and simulate signals in digital systems. LCD displays are used in a wide range of devices. The most common version uses a 2×16 character array.

 

You can use Digital Discovery to understand the operations of the LCD display. To do so, you need the following hardware and software.

 

Hardware

  1. Digital Discovery
  2. HD44780 LCD + Arduino LCD Keypad Shield
  3. Arduino Uno

Software which can be downloaded in Digilent Wiki

  1. Arduino Sketch
  2. Digilent Waveforms multi-instrument software application

 

Then, you can plug the HD44780 LCD on LCD Keypad shield and stack the module on the Arduino Uno. You also need to download the sketch to the Arduino board. After that, you need to connect the Digital Discovery to the HD44780 LCD. The below picture shows the hardware set-up.

 

image

 

Scopes digital signals in Logic Analyzer

 

After you open WaveForms software and turn on Logic Analyzer instrument, you can add the following signals and buses

  1. RS signal as a separate signal and set trigger mode to normal with triggering on a rising edge of the EN signal
  2. Clock signal
  3. A nibble data bus with a clock on the rising edge of the EN signal

 

image

You can try different command and look at each bus and signal. When commands of 0x01 (“clear display”) and data 0x50 (letter “P” encoded in ASCII) are sent, you can see the LSB and 3rd bit are driven respectively.

image

 

Go through the step by step guideline and get the example code in the Digilent Wiki