Translating characters received on a serial port to FieldTrip events

This page describes the tool serial2event, which is located in the directory realtime/utilities/serial2event, and whose purpose is to write events to a FieldTrip buffer when a character is received on a serial port. The tool was developed specifically to be run on the presentation machines in the DCCN's MRI labs in order to forward TTL pulses from the scanner to the FieldTrip buffer.

The user has the option to either only react on specific characters, and to write events with a fixed type and value, or to forward the received character as the value of the event. The sample field of the event can be auto-incremented, and reset by sending the string “RESET” to the UDP port (default = 1990) on which the tool listens. The latter feature is used in the DCCN's MRI lab to reset the sample counter when a new sequence is started on the scanner host (which is then picked up by the fMRI gui_streamer tool).

The tool is started from the command line by typing

serial2event [config-file]

If the config-file argument is not given, a default of serial2event.conf is assumed.

The operation mode of the tool is controlled by given a configuration file. A documented example follows below:

# Comment lines must start with a hash, empty lines are silently ignored
 
# buffer: FieldTrip buffer in the form hostname:port 
# without quotes
buffer=mentat069:1972
 
# serial: Parameters of the serial port in the form 
#   portname:baudrate:databits:stopbits:parity
# all numbers must be >=0, parity may only be 0 or 1
serial=COM3:115200:8:1:0
 
# character: specify single character to react on, or 
# comment this out to react to every incoming character
character=H
 
# type: Type of event as either an integer, double 
# precision number, or string (e.g. "serial")
type="serial"
 
# value: Value of event, can be integer/double/string 
# or @ to pass on serial character
value="click"
 
# sample: number to transmit with first pulse plus 
# increment per pulse, e.g. 0+1  (sends 0,1,2,3,...)
sample=-5+1
 
# offset and duration: integer numbers
duration=0
offset=0
 
# UDP port for RESET messages
port=1990

We provide a simple Makefile for the MinGW compiler or GCC. Please go to the realtime/utilities/serial2event directory and type make or mingw32-make. Note that you might need to compile the buffer library first.