RS-485 - Laptop interfacing

[smitchell]

read 485 on you latop

Hi, I need some basic info on how to get data from an RS-485 network into windows. Its for a monitoring network that we are putting together, and the computer being used will usually be a latop (no serial port).

Can someone give me a basic explaination of how I should interface the laptop to the network, and how i get the data from within the software that we have to write. Sorry, im still at uni and im new to this kind of thing...

Thanks heaps,

Sam

 

[cherrytart]

rs485 laptop

Basically, you need to get the signals from the RS-485 network into your laptop and that limits you to what your laptop supports.

Usually you would buy or build an RS-232 to RS-485 converter and some software, but without a serial port, this is useless.

There might be an RS-485 to parallel port converter somewhere out there.

Also, there are RS-485 and RS-232 PCMCIA cards. I would expect the RS-485 to cost more just because they are not as common, so it might be cheaper to use an RS-232 card and a converter.

 

[smitchell]

laptop rs 485

So once ive got the required adapters and its all hooked up, how do i access the data from within the software?

I read about some serial - USB converters that create a virtual com port. So how do i actually get the data from that port when writing a program in C++?

will it be different getting it from a virtual port as opposed to a real serial port on a PC?

Thanks,

Sam

 

[Pinczakko]

rs-485 laptop

I have programmed with virtual port using a toshiba laptop (in visual basic). The purpose is for simulation before trying the software in the real computer that has an RS-232 port. From the name itself (virtual com port), it implies that it should "looks like an ordinary com port" to us as the programmer, so we won't need "exotic" thing for our purpose. If you are using Microsoft Visual C++, you can use the MSCOMM32 ActiveX control to ease the development. I haven't try this compoenent in Borland C++ Builder (AFAIK C++ Builder also supports ActiveX controls), but it works fine in VB and VC++.

regards,

Pinczakko

 

[swapgo]

U find information from a book called "Serial Port Complete"

Regards
Gopi

 

[ME]

will it be different getting it from a virtual port as opposed to a real serial port on a PC?

No

When you attach the USB to serial converter, the converter is automaticaly given a COM port number and you can access it like a normal com port.

Please read my answers in this topic:



I would reccomed you to use Silabs CP2101, it's much more compact and integrated than the FTDI chips.
CP2101 has integrated EEPROM and Oscillator, which the FTDI Chips has not.
You only need a couple of capacitors.
But I'm not sure if the CP2101 works with RS485 ICs or only RS232. You have to find out about this first.
Otherwise you should use FTDI chips, there already RS485 examples, so it should be easy to design.
Silabs: www.silabs.com
FTDI: www.ftdichip.com