To read the data from serial device while something is being written over it. #for python2.7 data = ser.read(ser.inWaiting) #for python3 ser.read(ser.inWaiting) PDF - Download Python Language for free. Appearing at RPi2. If I add a time delay (time.sleep(3) for example) I get nothing. My guess is that it is only picking up data if it is sent at the same time as it is reading. Is there some way to reliably read everything that comes out of the serial port? (Maybe RPi2 store the input somewhere and read everything since its last read or something.).

Download the Serial Example: DSIPythonEX (zipped .py)

After python and the pyserial module has been installed on your system, this example code will send connect, send, and receive commands from our products:

# for PYTHON 3+ with pySerial module installed# DS INSTRUMENTS 2017 PYTHON SCPI REMOTE CONTROL EXAMPLE

import serial # use the serial module (https://pypi.python.org/pypi/pyserial)

import time # delay functions

badCommandResponse = b'[BADCOMMAND]rn’ # response if a command failed (b makes it into bytes)

ser = serial.Serial(“COM79”, 115200, timeout=1) #Change the COM PORT NUMBER to match your device

if ser.isOpen(): # make sure port is open

print(ser.name + ‘ open…’) # tell the user we are starting

ser.write(b’*IDN?n’) # send the standard SCPI identify command

myResponse = ser.readline() # read the response

print(b’Device Info: ‘ + myResponse) # print the unit information

time.sleep(0.1) # delay 100ms

ser.write(b’PHASE?n’) # try asking for phase

myResponse = ser.readline() # gather the response

if myResponse != badCommandResponse: #is this is not a phase shifter why print the error

print(b’Phase=’ +myResponse)

time.sleep(0.1) # delay 100ms

ser.write(b’FREQ:CW?n’) # try asking for signal generator setting

myResponse = ser.readline() # gather the response

if myResponse != badCommandResponse: # is this is not a signal generator why print the error

print(b’Frequency=’ + myResponse)

time.sleep(0.1) # delay 100ms

ser.write(b’ATT?n’) # try asking for step attenuator setting

myResponse = ser.readline() # gather the response

if myResponse != badCommandResponse: # is this is not an attenuator why print the error

print(b’Attenuation=’ + myResponse)

time.sleep(0.1) # delay 100ms

ser.write(b’FREQ:CW 3GHZn’) #lets change a setting now!

Bases: object

Instantiate a Serial object and open the tty device at the specifiedpath with the specified baudrate, and the defaults of 8 data bits, noparity, 1 stop bit, no software flow control (xonxoff), and no hardwareflow control (rtscts).

Return type:
Parameters:	devpath (str) – tty device path. baudrate (int) – baudrate. databits (int) – data bits, can be 5, 6, 7, 8. parity (str) – parity, can be “none”, “even”, “odd”. stopbits (int) – stop bits, can be 1 or 2. xonxoff (bool) – software flow control. rtscts (bool) – hardware flow control.
Returns:	Serial object.
Raises:	`SerialError` – if an I/O or OS error occurs. `TypeError` – if devpath, baudrate, databits, parity, stopbits, xonxoff, or rtscts types are invalid. `ValueError` – if baudrate, databits, parity, or stopbits values are invalid.

read(length, timeout=None)[source]¶

Read up to length number of bytes from the serial port with anoptional timeout.

timeout can be positive for a blocking read with a timeout inseconds, zero for a non-blocking read, or negative or None for ablocking read that will block until length number of bytes are read.Default is a blocking read.

For a non-blocking or timeout-bound read, read() may return less thanthe requested number of bytes.

For a blocking read with the VMIN setting configured, read() willblock until at least VMIN bytes are read. For a blocking read with bothVMIN and VTIME settings configured, read() will block until at leastVMIN bytes are read or the VTIME interbyte timeout expires after thelast byte read. In either case, read() may return less than therequested number of bytes.

Parameters:	length (int) – length in bytes. timeout (int, float, None) – timeout duration in seconds.
Returns:	data read.
Return type:	bytes
Raises:	`SerialError` – if an I/O or OS error occurs.

write(data)[source]¶

Write data to the serial port and return the number of byteswritten.

Parameters:	data (bytes, bytearray, list) – a byte array or list of 8-bit integers to write.
Returns:	number of bytes written.
Return type:	int
Raises:	`SerialError` – if an I/O or OS error occurs. `TypeError` – if data type is invalid. `ValueError` – if data is not valid bytes.

poll(timeout=None)[source]¶

Poll for data available for reading from the serial port with anoptional timeout.

timeout can be positive for a timeout in seconds, zero for anon-blocking poll, or negative or None for a blocking poll. Default isa blocking poll.

Parameters:	timeout (int, float, None) – timeout duration in seconds.
Returns:	`True` if data is available for reading from the serial port, `False` if not.
Return type:	bool

flush()[source]¶

Flush the write buffer of the serial port, blocking until all bytesare written.

Raises:	`SerialError` – if an I/O or OS error occurs.

Python Serial Read Example Free

input_waiting()[source]¶

Query the number of bytes waiting to be read from the serial port.

Returns:	number of bytes waiting to be read.
Return type:	int
Raises:	`SerialError` – if an I/O or OS error occurs.

output_waiting()[source]¶

Query the number of bytes waiting to be written to the serial port.

Returns:	number of bytes waiting to be written.
Return type:	int
Raises:	`SerialError` – if an I/O or OS error occurs.

close()[source]¶

Close the tty device.

Raises:	`SerialError` – if an I/O or OS error occurs.

fd¶

Get the file descriptor of the underlying tty device.

Type:	int

devpath¶

Get the device path of the underlying tty device.

Type: