RPi’s Rx (GPIO15) connects to the Tx of the other device.If the serial TTL port has to connect directly with the serial TTL port of another device with the same 3.3V UART voltage levels: The USB-serial board’s USB port connects to the USB port of a computer (desktop) via a USB-to-USB cable.The USB-serial board’s ground pin connects to RPI’s ground (because this is the reference ground for the UART voltages).RPi’s Tx (GPIO14) connects to Tx of the USB-serial board.RPi’s Rx (GPIO15) connects to the Rx of the USB-serial board.For this to occur, RPi’s 3.3V pin should be connected to the VCC terminal of the board. USB-serial boards also have an option to receive supply voltage directly from the Raspberry Pi. Be sure to select the 3.3V option before connecting to Raspberry Pi. Some USB-serial boards offer jumpers that can be set between 5 and 3.3V UART voltages. If a 5V USB-serial board is used, the TTL port channels of RPi can get permanently damaged. The one for use with Raspberry Pi must have 3.3V UART voltages. FTDIs are the oldest and most common one. There are several USB-serial boards available. However, if the enable_uart flag is set to 1 by default, then PL011 is the primary UART on that RPi model. If in the /boot/config.txt file, the enable_uart flag is set to 0 by default, then the mini-UART is the primary UART on that RPi model. It’s possible to know which UART type is the primary one by inspecting the /boot/config.txt file. The port can be addressed by name /dev/serial0.Īlternatively, /dev/ttyS0 or /dev/ttyAMA0 can be used as port names, depending on whether PL011 or mini-UART is the primary UART (on the respective Raspberry Pi model ). Reboot Raspberry Pi for these changes to take effect.Īfter rebooting RPi, its serial TTL port can be used for serial communication over the UART protocol.

Now, the serial TTL port (GPIO14 and GPIO15) are enabled for serial communication on Raspberry Pi.ħ. The configuration window will then ask you to enable the serial port hardware. The configuration window will ask if you’d like the login shell to be accessible over serial. In Raspberry Pi, open the Terminal window (Bash shell) and execute this command:Ģ. In this tutorial, we’ll learn how to use the Python Serial library to setup bidirectional communication with a computer.Īs discussed in the serial communication on Raspberry Pi tutorial, the default serial Linux console on Raspberry Pi OS must be disabled to use RPi’s serial TTL port for UART communication.įollow these steps to disable RPi’s serial Linux console:ġ. We also learned how to find a serial port name on Linux, Windows, macOS, and Raspberry Pi (RPi). In the previous tutorial, we discussed the universal asynchronous receiver-transmitter (UART) protocol and voltage levels, covering USB-serial boards and other serial adaptors.

Python serial library raspberry pi