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I now have a Raspberry Pi 3B, and a 3.5inch touch screen. The screen connects to the Pi by connecting to GPIO pin 1 to 26, so it holds up all the UART and I2C pins. However I would want to connect another device to the Pi by serial. Is there any possible way to achieve this with the remaining pins, like by emulation or something?

I have looked at many screens but they all seem to hold up GPIO 1 to 26, even for some ones that has HDMI connection, I suspect they use the GPIO to pull power. Does there exist any screen that does not hold up all the GPIOs?

Is it possible to initiate a parallel connection from I2C 3 and 5 while the screen is connected?

Or should I simply use the usb ports and connect to a USB-to-serial device?

I simply want to build a Raspbian with display and barcode scanning ability, perhaps there are better ways to go?

UPDATE:

Just a bit of update, I think I should be using USB instead so the question asked was no longer an issue, and did found a monitor that does not hold up the unused slotsKeDei Screen.

But I think pico hat hacker is the correct answer for this question, in fact I have just ordered one. so I am going to credit Mat for the answer, and thankyou Steve for your insight.

Jimmy Chi Kin Chau
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If its Adafruits 3,5 "

https://learn.adafruit.com/adafruit-pitft-3-dot-5-touch-screen-for-raspberry-pi/overview

Uses the hardware SPI pins (SCK, MOSI, MISO, CE0, CE1) as well as GPIO #25 and #24. GPIO #18 can be used to PWM dim the backlight if you like. All other GPIO are unused.

And YES you have to get a breakout as the Pico HAT Hacker from Pimoroni or eq to access the unused GPIOs.

MatsK
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GPIO "functions" such as SCK, MOSI, MISO, CE0, CE1 etc. are programmable at register level.

Jan Hus
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