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mruby_io_UART_en.md

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UART

  • A class that supports asynchronous serial communication.

Constructor

UART.new( id=nil, *params )

  • Generates a UART object by specifying the physical unit indicated by "id."
  • The default parameter values follow the settings below if possible.
    • Baud rate: 9600
    • Data bits: 8 bits
    • Stop bits: 1 bit
    • Parity: None
    • Flow control: None

Optional Parameters

param type description
baudrate Integer Baud rate (default 9600)
baud (Same as above)
data_bits Integer Data bits (default 8)
stop_bits Integer Stop bits (default 1)
parity Const Parity bit (default NONE)
flow_control Const Flow control (default NONE)
unit --- Specifies the unit (same as parameter "id")
txd_pin --- Specifies the TxD pin
rxd_pin --- Specifies the RxD pin
rts_pin --- Specifies the RTS pin
cts_pin --- Specifies the CTS pin

Parameter Constants

UART::NONE
UART::EVEN
UART::ODD
UART::RTSCTS

Example of use:

# Use UART1 with all default parameters.
uart1 = UART.new( 1 )

# Use the serial device with the specified device node at 19200 bps, even parity.
uart2 = UART.new("/dev/cu.usbserial1", baud:19200, parity:UART::EVEN )

Device-specific

  • Not all parameters may be supported.

Instance Methods

setmode( *params )

  • Changes the mode (parameters) of UART.
  • The parameter specification follows that of the constructor.

Example of use:

uart1.setmode( baudrate:38400 )

read( read_bytes ) -> String

  • Reads data of the specified number of bytes, read_bytes.
  • If the specified number of bytes has not arrived, it will block until they arrive.

Example of use:

val = uart1.read( 10 )

Note

  • If you do not want to block, you can check the number of bytes that can be read in advance using the bytes_available method.

write( string ) -> Integer

  • Sends data.
  • Returns the number of bytes sent.

Example of use:

uart1.write("Output string\r\n")

Device-specific

  • Depending on the low-level library or hardware FIFO used, the method may return before all data has been sent.
  • If there is a transmission buffer, and all data can be stored in the buffer, it probably won't block.

gets() -> String

  • Reads a line of string. Internally, it returns the byte sequence until "\n" in the read buffer.
  • If a complete line of data has not arrived, it will block until it arrives.

Example of use:

val = uart1.gets()

Note

  • If you do not want to block, you can check if reading a line is possible in advance using the can_read_line method.
  • The maximum character length depends on the size of the read buffer. If the buffer becomes full with data that does not contain a newline character, it will not be possible to read using gets.

puts( string ) -> nil

  • Sends one line and sends a newline code at the end of the argument string.
  • The newline code is LF only by default.

Example of use:

uart1.puts("Output string")

bytes_available() -> Integer

  • Returns the number of readable bytes in the read buffer.

Example of use:

len = uart1.bytes_available()

bytes_to_write() -> Integer

  • Returns the number of bytes of data in the transmission buffer that have not been actually sent.

Example of use:

bytes = uart1.bytes_to_write()

Note

  • For devices without a buffer, this function always returns 0.

can_read_line() -> bool

  • Returns true if reading a line of data is possible.

Example of use:

flag = uart1.can_read_line()

flush()

  • Block until transmission of data accumulated in the transmission buffer is completed.

Example of use:

uart1.flush()

clear_rx_buffer()

  • Clears the receive buffer.

Example of use:

uart1.clear_rx_buffer()

clear_tx_buffer()

  • Clears the transmission buffer.

Example of use:

uart1.clear_tx_buffer()

send_break( time )

  • Sends a break signal.
  • The time is optional and specified in seconds.

Example of use:

uart1.send_break( 0.1 )

Device-specific

  • Depending on the hardware, time may be fixed (e.g., 12 bits) and cannot be changed.