class UART -- duplex serial communication bus¶
UART implements the standard UART/USART duplex serial communications protocol. At the physical level it consists of 2 lines: RX and TX. The unit of communication is a character (not to be confused with a string character) which can be 8 or 9 bits wide.
UART objects can be created and initialised using:
from machine import UART uart = UART(1, 9600) # init with given baudrate uart.init(9600, bits=8, parity=None, stop=1) # init with given parameters
Supported paramters differ on a board:
Pyboard: Bits can be 7, 8 or 9. Stop can be 1 or 2. With parity=None, only 8 and 9 bits are supported. With parity enabled, only 7 and 8 bits are supported.
WiPy/CC3200: Bits can be 5, 6, 7, 8. Stop can be 1 or 2.
A UART object acts like a stream object and reading and writing is done using the standard stream methods:
uart.read(10) # read 10 characters, returns a bytes object uart.read() # read all available characters uart.readline() # read a line uart.readinto(buf) # read and store into the given buffer uart.write('abc') # write the 3 characters
Turn off the UART bus.
Return true value if there're characters available for reading. On some boards, the number of available characters is returned.
Read characters. If
nbytesis specified then read at most that many bytes, otherwise read as much data as possible.
Return value: a bytes object containing the bytes read in. Returns
Read bytes into the
nbytesis specified then read at most that many bytes. Otherwise, read at most
Return value: number of bytes read and stored into
Read a line, ending in a newline character.
Return value: the line read or
Write the buffer of bytes to the bus.
Return value: number of bytes written or
Send a break condition on the bus. This drives the bus low for a duration longer than required for a normal transmission of a character.