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?
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.