Questions about COM ports

[tarzan]

Can COM3 be used for (ECP LPT1) printer port? Can you do serial communications through printer port and picaxe using Programming Editor V4.1.10?

Why does the COM port that my HSP56 Micro-modem uses show as to be available in Options/Serial Port? When I change ports for the modem COM3-COM6 that port becomes available.

I’m using Windows HomeXP sp2 with Programming Editor V4.1.10

 

[hippy]

I don't really understand your question in its entirety, but it is feasible to route data sent to a COM port to an LPT port and vice-versa.

In MS-DOS this could I recall be done by the MODE command, and I'm sure the same can be done under Windows. What happens is that data sent to a physical COM or LPT port is intercepted and redirected to a different COM or LPT port, or a virtual COM or LPT port is created which redirects the data sent to it.

Data sent to a COM port redirected to an LPT port would however not necessarily be 'serial data' as such, although it could be; it would all depend upon what the redirection software did, and what that software thought was connected to the LPT port.

At a high level, it is similar to creating a virtual COM port for a USB attached serial port. If such a COM port exists, then the Programming Editor will usually think it can use it. On my PC I have virtual COM ports which allow data to be sent via TCP/IP to another PC in a similar way.

 

[tarzan]

My question about printer port arises from manual (AXE001_pic_electronics.pdf) MICROCONTROLLER INTERFACING CIRCUITS Section 3 page 41, which shows a 25way connector and connections to be made to PC. This lead me to believe that it might be possible to use printer port with Programming Editor.

As to a port being available when the modem is using it, should this not gray out that option in the serial ports tab.

Edited by - tarzan on 7/31/2005 12:49:01 AM

 

[hippy]

Thanks for the clarifications.

The 25-way D shown in the manual is for a 25-way serial port connector, not a 25-way parallel port connector. With modern PC's having 9-way serial ports and the only 25-way socket being a line printer port, I can understand how the confusion arose.

As to the COM port the modem is on not being greyed-out, that is perhaps because although the port has been assigned for modem use, nothing in the Windows OS has claimed use for it at the time.

If you start up the Programming Editor while the modem is actually in use you should find it is greyed-out, but I have sometimes seen ports greyed out when they should be available for use and not greyed-out when they aren't. The Programming Editor can only report what Windows tells it when asked, and something somewhere other than the Programming Editor is probably confused.

 

[tarzan]

Thanks for that explanation Hippy.