Uart Output On Gpio Pins; Uarts And Device Tree - ADEEPT AWR Wheeled Robot Manual

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for other purposes requires this default behaviour to be changed. On startup, systemd checks the Linux kernel
command line for any console entries, and will use the console defined therein. To stop this behaviour, the serial
console setting needs to be removed from command line.
●This can be done by using the raspi-config utility, or manually.
sudo raspi-config
●Select option 5, Interfacing options, then option P6, Serial, and select No. Exit raspi-config.
●To manually change the settings, edit the kernel command line with sudo nano
/boot/cmdline.txt . Find the console entry that refers to the serial0 device, and remove it, including the baud rate
setting. It will look something like console=serial0,115200 . Make sure the rest of the line remains the same, as errors in
this configuration can stop the Raspberry Pi from booting.
●Reboot the Raspberry Pi for the change to take effect.

27.3 UART Output on GPIO Pins

●By default, the UART transmit and receive pins are on GPIO 14 and GPIO 15 respectively, which are pins 8 and 10
on the GPIO header.

27.4 UARTs and Device Tree

● Various UART Device Tree Overlay definitions can be found in the kernel github tree. The two most useful
overlays are disable-bt and miniuart-bt .
●disable-bt disables the Bluetooth device and restores UART0/ttyAMA0 to GPIOs 14 and 15. It is also necessary to
disable the system service that initialises the modem so it doesn't use the UART: sudo systemctl disable hciuart .
● miniuart-bt switches the Raspberry Pi 3 and Raspberry Pi Zero W Bluetooth function to use the mini UART
(ttyS0), and restores UART0/ttyAMA0 to GPIOs 14 and 15. Note that this may reduce the maximum usable baudrate
(see mini UART limitations below). It is also necessary to edit /lib/systemd/system/hciuart.service and replace ttyAMA0
with ttyS0, unless you have a system with udev rules that create /dev/serial0 and /dev/serial1. In this case, use
/dev/serial1 instead because it will always be correct. If cmdline.txt uses the alias serial0 to refer to the user-accessible
port, the firmware will replace it with the appropriate port whether or not this overlay is used.
●There are other UART-specific overlays in the folder. Refer to /boot/overlays/README for details on Device Tree
Overlays, or run dtoverlay -h overlay-name for descriptions and usage information.
●For full instructions on how to use Device Tree Overlays see this page. In brief, add a line to the config.txt file to
enable Device Tree Overlays. Note that the -overlay.dts part of the filename is removed.
...
dtoverlay=disable-bt
...