I want to connect a UC15 3G Module to RPI 3B and use ppp protocol in order to connect RPI to internet over 3G. But the problem is that UART0 on RPI is already occupied by another device and also I can't use USB ports for this purpose. I think I should use SPI-2-UART or I2C-2-UART converters but I want to know is not there another way like multiplexing UART or like this?

  • Well, you can use USB to UART/TTL adapters, and so you can have as many as 100 UARTs for your Rpi. And if you are using Rpi4B, you can use up to 5 of its on board UARTs.
    – tlfong01
    Commented Jul 26, 2020 at 12:59
  • One way would be to use an Arduino to handle multiple serial connections for you but the simplest way would be to get a HAT as the USB ports are out. Some will use chips to change voltage levels so care needs to be taken. If this is an issue then look to add a USB hat to give more ports BUT power then may be an issue so you need ones with a separate power feed...
    – user115418
    Commented Jul 26, 2020 at 16:55
  • Forgot the obvious way - SC16IS752 is a dual port serial chip via I2C or SPI
    – user115418
    Commented Jul 26, 2020 at 17:03
  • Does this answer your question? How many serial ports are on the Pi 3?
    – MatsK
    Commented Jul 27, 2020 at 23:27
  • Can somebody help me please how to write a driver for a device in Raspbian? Commented Jul 30, 2020 at 6:05


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