Oh this is great! I took a read of the product Wiki and I can see the 'NC' pins you mentioned. Its starting to make sense!From what is published in your link to that screen, there are 4 unused pins on the 2x20 header.
These are the physical pin numbers (NC = not connected):
1NCPower positive (3.3V power)
17NCPower positive (3.3V power)
35NCGPIO interface
37NCGPIO interface
The first 2 are the 3.3V power pins (not GPIO, just power).
The other 2 are GPIO pins, corresponding to GPIO 19 (pin 35) and GPIO 26 (pin 37), confirming what aBUGSworstnightmare said above.
There doesn't seem to be any pictures of the back of the screen (without it mounted to a Pi). Some screens include a breakout for simple connections to unused GPIO pins, but I can't tell if this one does. If not then soldering your own or a GPIO expander would be required.
As others have said, I2C can be also be used for additional things.
Ive attached an image of the back of the screen. I dont know what im looking for but I cant see any obvious ways to use those spare pins.
Let me see if I have this correct: These spare pins can be used? (as they available and 2 of them are standard GPIO pins) BUT as you said: I will need a GPIO expander to breakout those pins for use?
For this test project I mostly just want a simple On/Off button which I believe only uses 1 standard GPIO pin + a ground pin: with the ground pin being unavailble I assume this is another deadend...darn.
This evening I have been debating switching up the LCD screen to a HDMI version: https://www.waveshare.com/wiki/4inch_HDMI_LCD
As far as I can tell it uses 26pins leaving plenty for other uses.
Im also considering switching to the Pi 3 A+ So i can easily connect the screen and the Pi via the attachment.
Thanks for everyones help. Its been really helpful so far!
Statistics: Posted by Paradoxx — Sun Apr 14, 2024 12:46 am