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pyb.UART

Classes

UART

Construct a UART object on the given bus.

Module Contents

class pyb.UART.UART(bus, mode, baudrate=328125, *, prescaler=-1, polarity=1, phase=0, bits=8, firstbit=MSB, ti=False, crc=None)

Construct a UART object on the given bus. For Pyboard bus can be 1-4, 6, ‘XA’, ‘XB’, ‘YA’, or ‘YB’. For Pyboard Lite bus can be 1, 2, 6, ‘XB’, or ‘YA’. For Pyboard D bus can be 1-4, ‘XA’, ‘YA’ or ‘YB’. With no additional parameters, the UART object is created but not initialised (it has the settings from the last initialisation of the bus, if any). If extra arguments are given, the bus is initialised. See init for parameters of initialisation.

The physical pins of the UART buses on Pyboard are:

  • UART(4) is on XA: (TX, RX) = (X1, X2) = (PA0, PA1)

  • UART(1) is on XB: (TX, RX) = (X9, X10) = (PB6, PB7)

  • UART(6) is on YA: (TX, RX) = (Y1, Y2) = (PC6, PC7)

  • UART(3) is on YB: (TX, RX) = (Y9, Y10) = (PB10, PB11)

  • UART(2) is on: (TX, RX) = (X3, X4) = (PA2, PA3)

The Pyboard Lite supports UART(1), UART(2) and UART(6) only, pins are:

  • UART(1) is on XB: (TX, RX) = (X9, X10) = (PB6, PB7)

  • UART(6) is on YA: (TX, RX) = (Y1, Y2) = (PC6, PC7)

  • UART(2) is on: (TX, RX) = (X1, X2) = (PA2, PA3)

The Pyboard D supports UART(1), UART(2), UART(3) and UART(4) only, pins are:

  • UART(4) is on XA: (TX, RX) = (X1, X2) = (PA0, PA1)

  • UART(1) is on YA: (TX, RX) = (Y1, Y2) = (PA9, PA10)

  • UART(3) is on YB: (TX, RX) = (Y9, Y10) = (PB10, PB11)

  • UART(2) is on: (TX, RX) = (X3, X4) = (PA2, PA3)

Note: Pyboard D has UART(1) on YA, unlike Pyboard and Pyboard Lite that both have UART(1) on XB and UART(6) on YA.

any() → int

Returns the number of bytes waiting (may be 0).

deinit() → None

Turn off the UART bus.

init(baudrate, bits=8, parity=None, stop=1, *, timeout=0, flow=0, timeout_char=0, read_buf_len=64) → Incomplete

Initialise the UART bus with the given parameters:

  • baudrate is the clock rate.

  • bits is the number of bits per character, 7, 8 or 9.

  • parity is the parity, None, 0 (even) or 1 (odd).

  • stop is the number of stop bits, 1 or 2.

  • flow sets the flow control type. Can be 0, UART.RTS, UART.CTS or UART.RTS | UART.CTS.

  • timeout is the timeout in milliseconds to wait for writing/reading the first character.

  • timeout_char is the timeout in milliseconds to wait between characters while writing or reading.

  • read_buf_len is the character length of the read buffer (0 to disable).

This method will raise an exception if the baudrate could not be set within 5% of the desired value. The minimum baudrate is dictated by the frequency of the bus that the UART is on; UART(1) and UART(6) are APB2, the rest are on APB1. The default bus frequencies give a minimum baudrate of 1300 for UART(1) and UART(6) and 650 for the others. Use pyb.freq to reduce the bus frequencies to get lower baudrates.

Note: with parity=None, only 8 and 9 bits are supported. With parity enabled, only 7 and 8 bits are supported.

read(nbytes: Any | None = None) → bytes

Read characters. If nbytes is specified then read at most that many bytes. If nbytes are available in the buffer, returns immediately, otherwise returns when sufficient characters arrive or the timeout elapses.

If nbytes is not given then the method reads as much data as possible. It returns after the timeout has elapsed.

Note: for 9 bit characters each character takes two bytes, nbytes must be even, and the number of characters is nbytes/2.

Return value: a bytes object containing the bytes read in. Returns None on timeout.

readchar() → int

Receive a single character on the bus.

Return value: The character read, as an integer. Returns -1 on timeout.

readinto(buf, nbytes: Any | None = None) → int

Read bytes into the buf. If nbytes is specified then read at most that many bytes. Otherwise, read at most len(buf) bytes.

Return value: number of bytes read and stored into buf or None on timeout.

readline() → None

Read a line, ending in a newline character. If such a line exists, return is immediate. If the timeout elapses, all available data is returned regardless of whether a newline exists.

Return value: the line read or None on timeout if no data is available.

sendbreak() → None

Send a break condition on the bus. This drives the bus low for a duration of 13 bits. Return value: None.

write(buf) → int

Write the buffer of bytes to the bus. If characters are 7 or 8 bits wide then each byte is one character. If characters are 9 bits wide then two bytes are used for each character (little endian), and buf must contain an even number of bytes.

Return value: number of bytes written. If a timeout occurs and no bytes were written returns None.

writechar(char) → None

Write a single character on the bus. char is an integer to write. Return value: None. See note below if CTS flow control is used.

CTS: Incomplete

to select the flow control type.

RTS: Incomplete

to select the flow control type.