# Re: serial function for the psych tool box

**URL:** <https://psychtoolbox.discourse.group/t/re-serial-function-for-the-psych-tool-box/1278>\
**Category:** Uncategorized\
**Created:** [June 15, 2000, 10:32pm UTC](https://psychtoolbox.discourse.group/t/re-serial-function-for-the-psych-tool-box/1278 "2000-06-15T22:32:35Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\
**Post date:** [June 15, 2000, 10:32pm UTC](https://psychtoolbox.discourse.group/t/re-serial-function-for-the-psych-tool-box/1278/1 "2000-06-15T22:32:35Z")

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Simon Khuu wrote:  
  

> \> Hi Allen,  
> \>  
> \> I am I correct in assuming that there is not yet a windows equilivant of  
> \> the function 'serial?'

I don't know the answer to that. I'll copy this reply to the Psychtoolbox  
forum, someone there would know the answer.  
  

> \>  
> \> If there is could you email me a copy of the dll  
> \> or the c source.  
> \> The reason is that I need a function in matlab that can open a parallel  
> \> port and send a number maker 1,2,3,4 etc to a neuroscan 4 ERP device for  
> \> labelling the onset and offset of the stimulus.

You are looking for a serial port function because you want to control the  
parallel port. Is this because you want the source to the 'serial' function  
for use as an example when writing a function to control the parallel port ?  
If so, then the dll file won't help you. Or are you using the terms  
'serial port' and 'parallel port' interchangeably, unaware that they are  
different ports, and that the PC has both ?  
  
And do you only mean labelling ? Or in addition to the label indicating  
the number of the trial, does the arrival time of the label signal to the  
ERP device the onset of the stimulus ?  
  
  

> \>  
> \> Could you suggest how I might go about doing this

I will comment on how you might go about controlling the parallel port from  
within Matlab.  
  
I can think of two approaches. I assume that your neuroscan 4 ERP device  
acts like a printer in that it receives a series of bytes from the windows  
computer and that the transfer of those bytes is synchronized between sender  
and receiver by handshaking lines on the parallel port. (The alternative is  
that a Matlab script would directly specify the states of pins on the port,  
and this 4 ERP device samples, at times undetermined by the sender, the  
states of those pins.)  
  
One option is to get MS Visual C++, find windows documentation describing  
the parallel port API, and write a C file which compiles to a mex file.  
Matlab is distributed with example mex projects and the Matlab API manual  
has annotated examples that get you up to speed fast on using the MEX API.  
The source code for the PsychToolbox also includes a blank psychtoolbox  
project to start from.  
  
The other approach would be to call MSDOS shell commands within Matlab to  
control a system interface to the port. I don't have any experience doing  
this sort of thing in Matlab for Windows. But I can say a few things about  
how it might look. I expect that you can issue DOS shell commands from  
within Matlab. So in Matlab you could direct a string to the parallel port  
device just as you would from the DOS shell, except wrap the shell command  
in quotes and whatever is the Matlab shell escape command. You might have  
to use matlab's "eval" there also, if you're passing a string in a matlab  
variable. Calling shell commands to direct a string to a port should be  
easy for anyone who knows DOS well. I don't. While this solution should  
be easy to implement, it's going to execute more slowly than a .mex file  
would.  
  
 Note that if the issuance of these numbers from the parallel port must  
coincide precisely with the stimulus onset, then either of these approaches  
might fail. There is more hope for the first than the second.  
  
 Also, if this ERP device doesn't use a printer handshaking protocol, the  
second approach wouldn't' work at all.  
  
  
 -- Allen  
  
  

> \> Hi Allen,  
> \>  
> \> I am I correct in assuming that there is not yet a windows equilivant of  
> \> the function 'serial?' If there is could you email me a copy of the dll  
> \> or the c source.  
> \>  
> \> The reason is that I need a function in matlab that can open a parallel  
> \> port and send a number maker 1,2,3,4 etc to a neuroscan 4 ERP device for  
> \> labelling the onset and offset of the stimulus.  
> \>  
> \> Could you suggest how I might go about doing this  
> \>  
> \> Your response will be much appreciated  
> \>  
> \> Simon  
> \> Human Vision Lab  
> \> University of Western Australia  
> \>