Garbage on LCD

Other Hardware Displays
1

I recently purchased a serial LCD and am very excited to start using it in my projects to get easy feedback and output from the program. I have communication successfully setup and can easily print strings.

But since it uses serial to receive data, when I program the Arduino I have to unplug the TX line from the Arduino board and as a result my LCD is powered the serial line is floating all over the place and so I get all kinds of garbage characters on the screen. I figured tying the serial line directly to ground might fix that problem when I disconnect the serial TX line but it didn't, so I tried tying it to ground through a resistor and surprisingly it worked! It also worked when I tied to 5V through a resistor My questions is why does it work with a resistor but not without one and does the resistor value matter (currently mine is 440 ohms)? And is there a better way?

Thanks!

2

when you connect a serial display to the pin 0/1 it mirrors the communication of the USB as it uses the same port.
Nothing to do to prevent this, just do a lcd.clearScreen() or equivalent in setup()

3

I was under the impression I had to take anything out of pins 0/1 before deploying code. Is that not true? Can I simply leave my LCD plugged in whole deploying code and run a clearDisplay() upon setup? If so that's much easier!

4

I tried deploying my code while the LCD remained plugged into pin 1, but the code never deployed properly. When I removed the wire from the pin it deployed fine however. So I am back to my original problem: when I remove the pin prior to deploying my code I get garbage characters all over my screen. Not a huge deal since my intention is to shortly thereafter redeploy code and at the beginning of setup I do clear the screen.

I just wanted to see if I could over come the temporary garbage characters by tying to ground/power and as I said it works fine if I tie it to power via a resistor. But I wanted to know if this was actually a common fix or if it is considered bad practice and if so what is the better way.

5

What Serial display do you have?
do you have a link?

Another option might be to use SoftwareSerial and use another pin if possible.

6

Here is the display: https://www.sparkfun.com/products/9568

I am not opposed to using software serial, but I am still intrigued to know if the current fix for keeping the display clean while removing the wire from the TX pin is good practice.