How To Configure Serial Port In Raspberry Pi

Use the Raspberry Pi Serial Port to Connect to a Device

This example shows how to create a connectionto a serial device, write data to the device, and read data from thedevice.

By default, the serial console in the customized version of Raspbian Wheezy on your Raspberry Pi™ hardware is enabled. To use the serialdev, the serial console must be disabled.

On the original Debian available for the Raspberry PI, the UART allow you to have a serial console so you can connect to it, without needing network nor SSH. It takes a few steps to change this default behavior so we can connect our Xbee (Series 1) to our RPI. By default Raspberry Pi’s UART pins (GPIO 14 and 15) are configured as a serial console. It outputs all the kernel data during boot. We need to free up these pins for our use.

Warning

Excessive voltage and current can damage the Raspberry Pi hardware. Observe the manufacturer’s precautions for handling the Raspberry Pi hardware and connecting it to other devices. For more information, see https://www.raspberrypi.org/technical-help-and-resource-documents.

Create a connection to the Raspberry Pi hardware using raspi.

Show the location of the Tx and Rx pins, GPIO14 (UART0_TXD) and GPIO 15 (UART0_RXD),on the GPIO header.

Raspberry Pi hardware uses +3.3V. Do not connect Raspberry Pi hardwaredirectly to devices that use higher voltages.

Connect the Raspberry Pi board to a +3.3V serial device.

  • To receive data, connect the GPIO 15 (UART0_RXD) pinon the Raspberry Pi board to the TxD pin on the serial device.

  • To transmit data, connect the GPIO 14 (UART0_TXD) pinon the Raspberry Pi board to the RxD pin on the serial device.

  • Connect a ground pin, GND, on the Raspberry Pi boardto the GND pin on the serial device.

  • Connect a +3.3V pin on the Raspberry Pi boardto the VCC pin on the serial device.

Before continuing, research the manufacturer’sproduct information to determine which baud rate, data bits, parity,and stop bit settings the serial device supports.

How To Configure Serial Port In Raspberry Pie

Use serialdev to create a connection tothe serial device and assign the connection to a handle.

In this example, the connection uses the default valuesfor baud rate (115200), data bits (8),parity ('none'), and stop bit (1).

If the serial device requires nondefault values, use a set ofoptional arguments to override those defaults.

This example overrides the default value of StopBits bysetting it to 2. It uses the other arguments tomaintain the correct sequence of arguments to the left of the rightmostoverriding value.

You can write values to the serial device.

This example writes two values to the serial device. It overridesthe default precision, uint8, by setting it to uint16.

You can also read an array of values from the serial port.

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This example reads a 100-element array of uint8 valuesfrom the serial device.

If the serial connection times out during read operations,you can adjust the time out period by assigning a new value to the Timeout property.

Raspberry Pi and the Serial Port

By default the Raspberry Pi’s serial port is configured to be used for console input/output. Whilst this is useful if you want to login using the serial port, it means you can't use the Serial Port in your programs. To be able to use the serial port to connect and talk to other devices (e.g. Arduino), the serial port console login needs to be disabled.

Needless to say you will need some other way to login to the Raspberry Pi, and we suggest doing this over the network using an SSH connection.

Disable Serial Port Login

To enable the serial port for your own use you need to disable login on the port. There are two files that need to be edited

The first and main one is /etc/inittab

This file has the command to enable the login prompt and this needs to be disabled. Edit the file and move to the end of the file. You will see a line similar to

T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

Disable it by adding a # character to the beginning. Save the file.

#T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

Disable Bootup Info

When the Raspberry Pi boots up, all the bootup information is sent to the serial port. Disabling this bootup information is optional and you may want to leave this enabled as it is sometimes useful to see what is happening at bootup. If you have a device connected (i.e. Arduino) at bootup, it will receive this information over the serial port, so it is up to you to decide whether this is a problem or not.

You can disable it by editing the file /boot/cmdline.txt

The contents of the file look like this

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

Remove all references to ttyAMA0 (which is the name of the serial port). The file will now look like this

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

Reboot

In order you enable the changes you have made, you will need to reboot the Raspberry Pi

How To Configure Serial Port In Raspberry Pi 1

sudo shutdown -r now

Test the Serial Port

A great way to test out the serial port is to use the minicom program. If you dont have this installed run

sudo apt-get install minicom

Connect your PC to the Raspberry Pi serial port using an appropriate serial port adapter and wiring, then open Putty or a similar serial terminal program on PC side. Setup a connection using the serial port at 9600 baud.

Now run up minicom on the Raspberry Pi using

minicom -b 9600 -o -D /dev/ttyAMA0

What you type into the minicom terminal screen should appear on the serial PC terminal and vice versa.