Today I was experimenting with setting up PowerSDR-SR40 for use with fldigi and other digital software, and I got everything talking to each other. When everything is working together, it makes operating digital so easy. So far, I got PSDR working with fldigi and Ham Radio Deluxe. I'm planning on getting it working with MMSSTV and EasyPal Digital SSTV program. I dont think there will be any problems, as they should set up the same as the ones I already got working.
There are 2 programs you will need in order to make everything play nice. First is "Virtual Audio Cable". it can be downloaded from here: http://software.muzychenko.net/eng/vac.html
When you get it, you will need to create 2 virtual sound devices. There are good instructions at the above website on doing this. One will be needed for receive, the other for transmit.
The other program you will need, and you will only need it for software that also controls the radio, such as fldigi and Ham Radio Deluxe, and that is "com0com", This creates virtual com ports to link the control aspects together. It can be gotten here: http://com0com.sourceforge.net/
You will need to create 1 pair of com ports for most applications. There are excellent pdf directions on how to do this at the above website.
Then go into Powersdr and set up the "CAT" section. Although some software will work using the identifier set for "SDR-1000", I've had better luck setting up emulating a TS-2000. Under CAT control, set the com port as the lower com port number that you created in the virtual com ports, I used COM5. Fldigi will use COM6 under its CAT settings. I used RIGCAT in Windows to control the SDR, and it plays nice. I have had some problems getting the external programs to control PTT, so I just use VOX for that. I used to use VOX in my Yaesu too when I ran digi modes.
To get audio to the programs, you need to set up virtual audio cable. I used Virtual Audio Cable #1 for audio out from PSDR and VAC #2 for the TX input audio. These settings will be found in the VAC tab in the audio settings in PSDR. The audio settings in fldigi are just the opposite - VAC2 is the output device, and VAC 1 is the input.
Once everything is talking, fldigi will read the frequency of the radio and you can then use the logger in fldigi, and it works like any other radio would with CAT control.
Ham Radio Deluxe sets up in a similar fashion.
To listen to your receive audio, should you choose to do so, VAC has a little utility called an Audio Repeater. You can set that up to input the proper VAC device as the input, and your soundcard that you use for your speaker audio as the output of the repeater.
There you have it, a basic overview as to how to set up different software so they will talk to eachother. Once they talk, operation is a breeze. I worked a little bit of the RTTY contest, and worked about 25 contacts in less than an hour with only 15 watts of TX power.
Good luck, and I hope this helps you get things working with your Software Defined Radio.