Help! I have garbage showing on my 16×2 LCD

July 11, 2018 11:42 am

Have you ever tried to bring up a display only to have it show you something like this?

Garbage On LCD

What are some common problems with LCDs showing garbage?

If it is a new design or a prototype using a common HD44780 style LCD, then it is almost certainly wiring or code.

Troubleshooting Wiring Problems: Ask someone else to check your connections. This may help ferret out the problem. Many times the “Vo” pin is misunderstood–it does not connect to your power supply.Try putting 1v on Vo as a test to see if that helps.

Troubleshooting Code Problems: Start with a known good code base. Many times, pin port directions or the pin assignments have errors. One good technique is to write test code that toggles only one of the control pins, then verify that the correct pin at the LCD is toggling. Repeat this for each of the other pins. This exercise checks the signal path from the code all the way to the LCD.

Module-specific troubleshooting tips

If it is a serial LCD with a stream-style interface (CFA-632 or CFA_634) check to make sure that the baud rate set on the module matches the baud rate in your code.

Additional serial port settings are: no parity, 8 data bits, 1 stop bit. Also, check to make sure that you use a “real” RS-232 port to talk to a “real” RS-232 module. Compared to UART (also called “Logic-Level” or “TTL”) the levels are inverted.

For mission-critical systems, we suggest our packet-based modules (CFA-533, CFA-631, CFA-633, CFA-635, or CFA-835. These modules use CRCs and acknowledges in their communications, so you know 100% that what you intended is what happens.

Crystalfontz Support - Yes!

Still Getting Garbage?

Sometimes it happens that things do not work out perfectly. That is why Crystalfontz offers real, live tech support.

Whether it is bringing up a new design, finding a new display for an existing design, or even getting an LCD to work on a Raspberry Pi or Arduino project, we are here to help.

All these options can be a bit confusing to sort out, so we are here to help with application assistance to determine the optimal display for your design.

Please feel free to give us a call, chat or email, all the options to reach our team are shown on this page:

https://www.crystalfontz.com/support/

We won’t let you fail!

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