class Serial

With the serial module you can sent and receive data using serialport 1 to 4, the NMEA and SDI-12 port or to communicate with the cellular network modem.

Constructor

class omc048.serial(port, ...)

Create an serial object associated with the serial port specified. With no additional parameters, the serial object is created but not initialised (it has the settings from the last initialisation of the port, if any). If extra arguments are given, the bus is initialised. The parameters of the init function can be used after the port argument to initialise the port.

  • port is the id of the port and can be one of the following strings or integers:

  • serial1 (1)

  • serial2 (2)

  • serial3 (3)

  • serial4 (4)

  • nmea (5)

  • sdi12 (6)

  • modem (7)

Methods

serial.init(baudrate=9600, mode=RS232, bits=8, parity=None, stop=1, flow=0, timeout=10, timeout_char=0, rxbuf=128, txbuf=128)

Initialize the serial port for usage with the given parameters:

  • baudrate The clock rate to set the port.

  • mode The mode to initialize the serial output chip in, serial.RS232, serial.RS422 or serial.RS485.

  • bits The number of bits per character, 7 or 8.

  • parity The parity, None, serial.EVEN (0) or serial.ODD (1).

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

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

  • rxbuf is the character length of the read buffer.

  • txbuf is the character length of the write buffer.

This method will raise an exception if the baudrate could not be set within 5% of the desired value.

Note: With parity=None, only 8 bits is supported. With parity enabled, 7 and 8 bits are supported. Note: SDI-12 port baudrate is tested up to 1200 baud, NMEA and serial port baudrate is tested up to 115200 baud

serial.deinit() → None

Turn off the port.

serial.any() → integer

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

serial.read([nbytes: integer]) → 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 timeout_char elapses.

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

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

serial.read_char() → integer

Receive a single character on the bus.

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

serial.write(message: bytes) → integer

Write the buffer of bytes / str to the bus.

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

Note: Writing data is not supported on the NMEA port

serial.write_byte(byte: integer) → integer

Write a single character on the bus. byte is an integer to write.

Return value: None. See note below if CTS flow control is used.

serial.send_break() → None

Send a break condition on the bus. This drives the bus low for a duration of 13 bits. For some sensors this is used to wake them up.

Return value: None.

serial.spy_on(eol_char='', date_timestamp=False) → None

Initialize the spy for usage with the given parameters:

  • eol_char The End Of Line Character, to determine if the next byte is printed with a timestamp. When no eol_char is given the timestamp will be added every new second if data is received or sent.

  • date_timestamp The default value is timestamp only, it can be extended with a date in case of need by using True.

A serial byte sniffer. This will sent a copy of the sent and received data to the REPL interface. The data will be represented with a timestamp and the direction of the data.

Return value: None.

serial.spy_off() → None

This will turn off the sniffer functionality of the specific serial port.

Return value: None.

serial.redirect() → None

Non stop redirect of the byte data from the serial port to the REPL interface and from the REPL interface to the serial port.

Return value: None.

Note: The redirect can be stopped by using CTRL + C.

Constants

replace serial with the name of the serial port object.

serial.RS232
serial.RS422
serial.RS485

to select the mode.

serial.RTS
serial.CTS

to select the flow control type.’

Example

The following code shows an example with the serial read a message from serial 4 and resending it over serial ports 3 and 4.

import omc048

s4 = omc048.serial("serial4")
s4.init(9600, s4.RS232, bits=8, parity=None, stop=2, flow=0, timeout=0)

s3 = omc048.serial(3)
s3.init(115200, s3.RS485)

while True:
    if s4.any() > 0:
        message = s4.read()
        print(message)
        s4.write(message)
        s3.write(message)

The following code shows an example with the serial spy on port serial 3 and 4.

import omc048

s4 = omc048.serial(4)
s4.init(9600, s4.RS232, bits=8, parity=None, stop=2, flow=0, timeout=0)
s4.spy_on()

s3 = omc048.serial(3)
s3.init(115200, s3.RS485)
s3.spy_on('\r')

The following code shows an example of the serial redirect on port serial 1.

import omc048

s1 = omc048.serial(1)
s1.init(115200, s1.RS232)
s1.redirect()