1. Raspberry Pi Serial Port Number 2
2. Raspberry Pi Serial Port Name
3. Raspberry Pi Two Serial Ports
4. Raspberry Pi Serial Port Number List
5. Ps/2 Port

To develop your projects with Arduino or ESP8266 on Raspberry Pi basis, one may need to access the serial port for the update. This tutorial should work on all distributions of Linux and Raspbian in particular.

Introduction to Raspberry Pi Serial Ports. The Raspberry Pi UART transmit (TXD) and receive (RXD) pins are assigned to GPIO14 and GPIO15 respectively: Note that these pins use 3.3V logic levels so you can’t connect them directly to devices that uses 5V like an Arduino UNO or a PC. Technically, the Raspberry Pi has two UARTs: PL011 UART and mini UART. Dec 07, 2017  Programming the Raspberry Pi for Serial Writing. The second import is serial. This library contains all the functionality to deal with serial connections, this allows reading and writing through the serial ports. Ser = serial.Serial( port=' /dev/ttyS0', #Replace ttyS0 with ttyAM0 for Pi1,Pi2,Pi0 baudrate = 9600.

Back to RPi Advanced Setup.

The serial port is a low-level way to send data between the Raspberry Pi and another computer system. There are two main ways in which it can be used:

• Connecting to a PC to allow access to the Linux console. This can help to fix problems during boot, or to log in to the Raspberry Pi if the video and network are not available.
• Connecting to a microcontroller or other peripheral which has a serial interface. This can be useful if you want the Raspberry Pi to control another device.

• 2Connection to a PC
• 3Connection to a microcontroller or other peripheral
  • 3.2S/W: Preventing Linux from using the serial port

Connections and signal levels

The Raspberry Pi serial port consists of two signals (a 'transmit' signal, TxD and a 'receive' signal RxD) made available on the GPIO header. To connect to another serial device, you connect the 'transmit' of one to the 'receive' of the other, and vice versa. You will also need to connect the Ground pins of the two devices together.

The Broadcom chip at the heart of the Raspberry Pi has low power serial ports with limitations of voltage and protocol compatibility. The ports use 0V and 3.3 V logic levels, not 0 & +5V TTL levels or the +/-12 V used by RS-232 serial ports found on some older PCs. If you wish to connect one of these, you need a board or adapter to convert the signal levels. See this tutorial for one example on how to build a 3.3 V to RS-232 level converter with a breadboard, a MAX3232CPE IC and five 0.1 µF capacitors. If your Raspberry Pi has bluetooth/wireless capability, then the on-chip UART connected to the header pins is the less capable mini-UART with no break detection, no framing errors detection, no parity bit, no receive timeout interrupt and no DCD, DSR, DTR or RI signals (See RPi UART info for more details.)

If you wish to connect your Raspberry Pi to a PC with a USB port, the simplest option is to use a USB-to-serial cable which uses 3.3 V logic levels (e.g. the Adafruit 954 cable, the FTDI TTL-232R-RPI cable, or the Debug Buddy ultimate serial port). These can be simply plugged in directly to the GPIO header (see illustration).

• For using the Adafruit 954 cable on Windows, see Adafruit 954 USB serial cable.

If you wish to connect to a peripheral which has 0/5 V signals, you should ideally have a circuit to convert between the voltage levels. See this tutorial for an example using a ready-made level shifter module. Other circuits for level shifting are shown at RPi_GPIO_Interface_Circuits#Level_Shifters. The Debug Buddy ultimate serial port can also be configured for 0/5 V signals.

NOTE FOR RASPBERRY PI 3: The Raspberry pi 3 has changed things a bit and you might need to add the option enable_uart=1 at the end of /boot/config.txt (see this post by a Pi Engineer)

Raspberry Pi Serial Port Number 2

Connection to a PC

You can connect the Raspberry Pi to a PC using a USB-serial cable, or (if it has an RS-232 port) a level-converter circuit - see above for details. When this is done, you will need to set up a terminal emulator program on your PC as described below.

Console serial parameters

The following parameters are needed to connect to the Raspberry Pi console, and apply on both Linux and Windows.

• Speed (baud rate): 115200
• Bits: 8
• Parity: None
• Stop Bits: 1
• Flow Control: None

Linux terminal set up

If your PC is running Linux, you will need to know the port name of its serial port:

• Built-in (standard) Serial Port: the Linux standard is /dev/ttyS0, /dev/ttyS1, and so on
• USB Serial Port Adapter: /dev/ttyUSB0, /dev/ttyUSB1, and so on.
  • Some types of USB serial adapter may appear as /dev/ttyACM0 .

You will need to be a member of the dialout group to access this port (for later releases the required group is tty). You can check which is needed with:

and you will see something like 'crw-rw----T 1 root dialout .', c means character device, and root can 'read,write' and the group dialout can 'read,write' to the port and everyone else cannot access it.

To find out if you, the current user, is in the group dialout, use the command:

If you do not see dialout listed, add yourself with the command

You then have a choice of terminal emulation programs:

• Super Easy Way Using GNU Screen

Enter the command below into a terminal window

To exit GNU screen, type Control-A k.

• Super Easy Way Using Minicom

Run Minicom with the following parameters:

You can exit Minicom with Control-A x

Note: If you haven't configured minicom before (i.e: first use after installation), or if you find that your keyboard key presses are not sent to the RPi, you should make sure Hardware Flow Control is disabled. See Tedious Old-Fashioned Way Using Minicom to configure minicom.

• Tedious Old-Fashioned Way Using Minicom

Another method to setup minicom is described in the Tincantools Minicom Tutorial

• GUI method with GtkTerm

Start GtkTerm, select Configuration->Port and enter the values above in the labeled fields.

Network connection with the point-to-point protocol (ppp)

Raspberry Pi Serial Port Name

The easiest way to set up a network connection between your Raspberry Pi and another computer is with an Ethernet cable. If this is not possible, as is the case for the Raspberry Pi Model A, you can set up a connection over the serial cable. This uses the Point-to-point Protocol (PPP). A network connection running over a serial cable can be very useful for copying files onto the Raspberry Pi.

Step 1: Log in to the Raspberry Pi over the serial cable and run the Point-to-Point Protocol Daemon:

Some garbage will start appearing in the terminal. This is the cue to quit your terminal program and proceed to step two.

Step 2: On your local computer, start the Point-to-Point protocol. On a Linux or Mac computer you can do this by typing:

replacing /dev/tty.usbserial-FTGCC2MV with the name of your serial port. In the above line, 115200 is the baud rate of the connection, 10.0.0.1 is the local internet protocol (IP) address, the address you want your computer to have. 10.0.0.2 is the remote IP address, it is the address that the Raspberry Pi will have.

Test the connection:

Virtual connection to the LAN

Instead of 10.0.0.0/8 you could as well use normal 192.168.0.0/16 addresses;the first address must be the real address of the local (serving) system.You can chose the second address; it must not yet be assigned on the LAN (and be outside the DHCP range).The advantage is that the system connected to the serial line will appear as if it is directly connected to the LAN (arp protocol).

You must enable routing on the system directly connected to the LAN for other systems to access the system connected to the serial line:

On the guest system connected via the serial cable you must set the default route pointing to the serving system, e.g.

You should also configure /etc/resolv.conf if you want to use DNS.

Windows terminal set-up

Users of Windows Vista or later will need to download a terminal program, for instance PuTTY, or TeraTerm. Users of Windows XP and below can choose between using PuTTY and the built-in Hyperterminal.

PuTTY users simply need to choose 'serial', select the correct COM port and set the speed, as shown in the dialog below.

If you are unsure of the COM port, run [Device Manager] and look under 'Ports'. USB-attached serial adapters should have the name of the adapter shown (the Adafruit cable comes up as 'Prolific USB-to_Serial Comm Port'.

Boot messages

If your connection is set up correctly, when the Raspberry Pi is booted you should see many messages as the system comes up:

and so on. Eventually, you should see a login prompt:

You can then log in as you would with a keyboard and screen.

Unwanted serial garbage input

Note that on older software by accident the internal pullups of the RxD GPIO pins were not enabled, this could lead to lots of serial garbage being picked up if the GPIO pin was touched, or even if a finger was nearby. In extreme case this could lead to kernel warnings and other problems.

Connection to a microcontroller or other peripheral

H/W considerations

If your microcontroller or peripheral works with 5V logic levels, level conversion is necessary - see 'Connecting to a PC' for details.

If your microcontroller or peripheral works with 3.3V logic levels then you can connect its TxD, RxD signals directly to the RxD and TxD pins of the Raspberry. However it's probably a good idea to connect the signals with a 2.2 kΩ resistors in series. This will prevent damage if two outputs are accidentally connected together (e.g. if you connect TxD with TxD or if a GPIO input pin is accidentally programmed as output).

S/W: Preventing Linux from using the serial port

By default Linux will grab the serial port and use it as a terminal. If you want to use it for other purposes you must prevent this. Here are the methods you can use:

Method 1, raspi-config (easiest, try this first)

Run sudo raspi-config and check if it has the option advanced options -> serial. If it has, set it to disabled and you're done.

Method 2, using an existing script (easy)

There's a nice little script to automate the steps bellow.

Raspberry Pi Two Serial Ports

Method 3, manual configuration (complex)

free up mac spac app If neither raspi-config nor the script works for you then follow the hard way.

NOTE FOR RASPBERRY PI 3: The Raspberry pi 3 has changed things around a bit: ttyAMA0 now refers to the serial port that is connected to the bluetooth. The old serial port is now called ttyS0. So if you have an RPI3, everywhere you see 'ttyAMA0' below, you should read 'ttyS0'.

The Broadcom UART appears as /dev/ttyAMA0 under Linux. There are several minor things in the way if you want to have dedicated control of the serial port on a Raspberry Pi.

• Firstly, the kernel will use the port as controlled by kernel command line contained in /boot/cmdline.txt. The file will look something like this:

The console keyword outputs messages during boot, and the kgdboc keyword enables kernel debugging. You will need to remove all references to ttyAMA0. So, for the example above /boot/cmdline.txt, should contain:

You must be root to edit this (e.g. use sudo nano /boot/cmdline.txt). Be careful doing this, as a faulty command line can prevent the system booting.

• Secondly, after booting, a login prompt appears on the serial port. This is controlled by the following lines in /etc/inittab:

Raspberry Pi Serial Port Number List

You will need to edit this file to comment out the second line, i.e.

Finally you will need to reboot the Raspberry Pi for the new settings to take effect. Once this is done, you can use /dev/ttyAMA0 like any normal Linux serial port, and you won't get any unwanted traffic confusing the attached devices.

The above instructions have been verified on Raspbian 'Wheezy'; other distributions may be set up differently. To double-check, use

to show the current kernel command line, and

to search for getty processes using the serial port.

A tutorial on accessing the Raspberry Pi's serial port from Python is available at Serial_port_programming.

Handshaking lines

You can have the RTS0 signal on GPIO 17 (P1-11) or GPIO 31 (P5-06) if you set them to ALT function 3. Likewise, the CTS0 is available on GPIO 30 (P5-05), if it is set to ALT function 3. You can control the settings of I/O pins with gpio_setfunc.

Glitch when opening serial port

When the serial port is opened the voltage on TXD pulses negative for approximately 32 µs (regardless of the baud rate). This pulse may be interpreted as a transmission by a device connected to the TXD pin, which could have unintended effects. An error tolerant communication protocol should be used to avoid problems this glitch could cause. Another method for avoiding problems is to use a GPIO pin to implement the RTS signal, and to have the connected device ignore all data on TXD until RTS is asserted. If the connected device is susceptible to the glitch and cannot be modified, it is sometimes possible to obtain correct operation by opening the serial port in advance of initiating transmission. This can be done in the shell with the sleep program:

In a shell script, the following commands may be used to kill the sleep process once serial transmission is complete.

Over the past couple of years, I’ve installed operating systems on a number of little boards and I have to say, that while the Raspberry Pi with Raspbian is generally the easiest when it comes to enabling GPIO, the serial port can be a pain.

Here is how to ease the pain.

It completely escapes me why user Pi (the one everyone recommends you use) does not by default have access to the serial ports. This is, after all supposed to be an educational machine, not an example of a security system. There are generally two problems with serial… Pi doesn’t have access and this is by default used for debugging (apparently, though I’ve never used it for that). There have been various explanations as to how to get around this… editing out the bit in /boot/cmdline.txt that refers to the serial port seems to be the important one.

Ps/2 Port

You might expect the serial port, being the only one available, to be called /dev/ttyS0, but you would be wrong, it is /dev/AMA0

You need to give user Pi permission – at the command line prompt…

/pacman-world-3-download-pc.html. sudo usermod -a -G dialout pi

That’s a one-off. Done. Now turn off the debugging serial.

Remove references to /dev/ttyAMA0 from /boot/cmdline.txt – which sets up the serial console on boot.

If you have similar references in /etc/inittab do the same. I don’t have that file.

Lastly for Node-Red users, the SERIAL node can be iffy to upgrade. Follow the recommendations from the Node-Red designers if you have trouble. I did have minor trouble on one older installation, not on a new installation. Thanks to their advice the problem went away.

This link is for installing/upgrading Node-Red on the Pi and refers to serial port node issues. https://nodered.org/docs/hardware/raspberrypi

While I’m here – I2c on the PI… (enable if you want to use it) on most boards I’ve set up you need pull-up resistors on data and clock lines, on the Pi these seem to be already fitted. I2c is ready to go.