240x320 LCD Touch Display Shield - Analog A5 input OK to use?

Other Hardware Displays
1

I have a battery test project to measure external voltages on analog pin A1 that uses for display an Arduino Duo with the 16x2 character LCD display shield (https://www.ebay.com/itm/16x2-Blue-LCD-Display-Keypad-Shield-for-Arduino-HD44780/264473986304). Works great and is a nice physically compact package (i.e. no breadboard with jumpers and such).

However, I want more display capability than 16x2 so I want to switch to the 240x320 LCD display (https://www.ebay.com/itm/2-4-Inch-LCD-Display-240x320-SPI-TFT-White-LED-OLED-LCD-Serial-Port-Module-n/113893451627). But I still need an analog input pin.

Inspecting the 240x320 shield I see A1-A4 are labeled (and assume used) but not for A5. A5 "appears" to be unused (i.e no apparent PC traces going to it top or bottom). I monitored A5 (analogRead) and see a fluctuating count which makes sense as the pin is floating. If I ground pin A5 I read a value of zero and the display continues to happily work. All seems OK.

But if I apply a voltage (less than 5Vdc of course) to A5 the display ceases to work. That is all I get is a white screen when booting the Arduino.

Questions;

  1. Is pin A5 being used by the 240x230 shield?
  2. What, if any, analog pin is available to me on this shield?
  3. Will another type of Arduino work that has more analog inputs (and still allow the 240x230 shield to plug in directly without jumpers and such)? Which do you suggest?
  4. Am I screwed? :wink:

Thanks, John

2

Your link shows a 2.4 inch Shield pcb and also a 2.4 inch SPI pcb (which is not a shield)

Please compare the item on your desk with the photos of the pcb on your link.

Yes, you can use A5 for Analog. It is not used by the Shield.
You can snip off the A5 pin from the Shield.
Then use an angle pin to access A5 socket on the Arduino.

If you have a nice Uno clone, these tend to have A6, A7 holes. So you can have three Analog signals.

David.

3

David,

Thanks for the reply. As it turns out I came up with the same inelegant solution as you of cutting the unused A5 pin of the display board. You have to cut is very close and file it down so that you don't make contact with your external lead.

Actually it is leads (plural) as I also need to get to ground on the Duo. So cut another pin on the display board. As it turns out there are two grounds between the Vin and 5V pins. One of the grounds is needed by the display board and marked "GND". The other ground pin is unmarked and unused. Someone was thinking ahead.

Thanks again, John

4

Most Uno clones have got extra GND holes. You can either solder angle male or straight female.
Many have extra A5, A6, A7 holes,

So there are several ways to connect external sensors with a mounted Shield.

I do not know what a DUO is.
An Arduino DUE has many extra Analog pins and two GND on the 18x2 header.

David.

5

Correction: I am using an Arduino Uno! Not Due (or Duo as I incorrectly said). Boy, my Italian is bad!

Again, thanks for the help.

  • John