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I was wondering if I have both a Bluetooth HC-05 module and a GPS module (uBlox 7N) is it possible both for both to be using the serial interface?

I'm aware they cant be operating simultaneously with one another but if I using the RX TX pins for the GPS module, can I receive a location, store it in a variable then terminate the GPS serial usage and using software serial with 2 pins of my choice transmit data via the Bluetooth module which also requires the serial pins?

  • No, you can not do it on one serial interface. However you can use Software Serial library and "create" second serial interface. – Mike Petrichenko Aug 27 '18 at 5:05
  • Yes, you can use multiple SoftwareSerial ports, but you can listen only at one at a time. The easiest solution is a arduino mega 2560 board with 3 extra hardware serial ports. – Jot Aug 27 '18 at 15:45
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You are right, that you need one Serial interface for each module. The Uno has only 1 hardware serial interface (hardware means, that the Arduinos hardware will do the communication work in the background and you can let it do other things in the meantime). But you can add more serial interfaces, on other pins, that work purely through software. For this the SoftwareSerial library is meant.

SoftwareSerial comes with some limitation, since the load of communication has to be done in software instead of hardware. For example it becomes unstable at high baudrates. Especially for the HC-05 you should not use baudrates of 115200 baud and higher. Also - since it uses pin change interrupts to work - you can only listen at one SoftwareSerial at any given time.

Since you only have 2 modules, it should be easily possible, to utilize SoftwareSerial and access both of them with the Uno. If you at some time want to use more serial modules, you can still change to a bigger board like the Mega.

Note: Be sure to disconnect the module from the hardware serial, before programming the Uno over the Serial interface (USB), or the programming will fail.

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