Raspberry Pi Serial Port Uart Tutorial
The Raspberry Pi has three types of serial interface on the GPIO header. You're probably already familiar with the UART serial port, which allows you to open a login session from a serial terminal application, such as PuTTY. The other two serial interfaces are the Serial Peripheral Interface (SPI) and Inter-Integrated-Circuit bus (I2C). When we use serial0 as UART port instead of ttyS0 or ttyAMA0 then the program written for Raspberry Pi 3 will also run on older models of Raspberry Pi. Swapping Serial Ports on Raspberry Pi 3. For better performance, serial communication on GPIO14 and GPIO15 needs to use ttyAMA0 port which is connected to the Bluetooth module.
This answer is still correct, and explains in more detail the nature of the changes, but most users of current Raspbian should just run sudo raspi-config Select Interfacing Options / Serial then specify if you want a Serial console (probably no) then if you want the Serial Port hardware enabled (probably yes). Then use /dev/serial0 in any code which accesses the Serial Port. The BCM2837 on the Raspberry Pi3 has 2 UARTs (as did its predecessors), however to support the Bluetooth functionality the fully featured PL011 UART was moved from the header pins to the Bluetooth chip and the mini UART made available on header pins 8 & 10.
Raspberry Pi Uart Console
This has a number of consequences for users of the serial interface. The /dev/ttyAMA0 previously used to access the UART now connects to Bluetooth. The miniUART is now available on /dev/ttyS0. In the latest operating system software there is a /dev/serial0 which selects the appropriate device so you can replace /dev/ttyAMA0 with /dev/serial0 and use the same software on the Pi3 and earlier models. Unfortunately there are a number of other consequences:- The mini UART is a secondary low throughput UART intended to be used as a console. The mini Uart has the following features:. 7 or 8 bit operation.
1 start and 1 stop bit. No parities. Break generation. One click unbrick android. 8 symbols deep FIFOs for receive and transmit. SW controlled RTS, SW readable CTS.
Auto flow control with programmable FIFO level. 16550 like registers. Baudrate derived from system clock. There is no support for parity and the throughput is limited, but the latter should not affect most uses. There is one killer feature 'Baudrate derived from system clock' which makes the miniUART useless as the this clock can change dynamically e.g.
Raspberry Pi Enable Uart
If the system goes into reduced power or in low power mode. Modifying the /boot/config.txt removes this dependency by adding the following line at the end:- corefreq=250 This fixes the problem and appears to have little impact. The SPI clock frequency and ARM Timer are also dependent on the system clock. For some bizarre reason the default for Pi3 using the latest 4.4.9 kernel is to DISABLE UART. To enable it you need to change enableuart=1 in /boot/config.txt. (This also fixes the corefreq so this is no longer necessary.) Finally if you don't use Bluetooth (or have undemanding uses) it is possible to swap the ports back in Device Tree.
Raspberry Pi Uart Voltage
There is a pi3-miniuart-bt and pi3-disable-bt module which are described in /boot/overlays/README. Finally this got work for my pi3 (os: debian jessie) please follow these 6 steps carefully. Step 1 - Install Raspbian Jessie onto a SD card and boot the Pi when connected to a network Login via terminal or desktop and shell Configure the system with: sudo raspi-config Expand filesystem and enable serial on advanced page, exit and reboot.
Step 2 -this won't necessary if you have jessie new release Update the system with: sudo apt-get update sudo apt-get upgrade Step 3 - Device Tree settings as below: Add device tree to /boot/config.txt to disable the Raspberry Pi 3 bluetooth. Sudo nano /boot/config.txt Add at the end of the file.if you want to change the blutooth to miniuart port(bad) dtoverlay=pi3-miniuart-bt.if you want to disable the blutooth(good) dtoverlay=pi3-disable-bt Exit the editor saving your changes. Step 4 - reboot the pi sudo reboot step 5 - a)to disable the Serial Console edit the file using sudo nano /boot/cmdline.txt remove the word phase ' console=serial0,115200' or ' console=ttyAMA0,115200' Exit and save your changes b)to Enable the Serial Console edit the file using sudo nano /boot/cmdline.txt Change the file to the following: dwcotg.lpmenable=0 console=tty1 console=serial0(or ttyAMA0),115200 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait Exit and save your changes Step 6 - reboot the pi sudo reboot - that's all,have fun.