VI for LTC 2400

[sylvester]

Hi,

I got a LTC 2400  24-bit A/D converter with a serial interface, DC 228. There is a demo software included, 2400demo.exe, written in Labview 4.

I am looking for the VI for this program to include that in my labview project.

I appreciate any help!

[Dennis_Knutson]

The LTC2400 is an A/D chip from Linear Technology. Who makes the board that this is on and from whom do you get the example program? Have you asked them for the source code or a driver? Did you get a programming manual?

[sylvester]

I got the LTC 2400 together with a target board, which seems to be the DC 228 evaluation board also from Linear technology. It has a sub-D 9 pin connector for direct connection to a serial port.  The software LTC2400v1.01 is a compiled program in Labview 4.01 (1999). It reads the A/D converter using either COM1 or 2 (selectable). I could neither get more information from the vendor nor from the Linear technology home page (too old? The DC 228 is not mentioned). It seems as if the board does not use real serial communication but rather uses 3 lines with a different protocol. The source code would probably explain the details.

[Dennis_Knutson]

It sounds like someone from Linear Technology created this program a very long time ago. If no one there can locate the source code, then there's not much you can do. If you are interested in trying to understand how the communication is done, you could try a program called portmon. This will allow you to monitor the serial port.

How do you know it uses some unique protocol? Serial communication only requires 2 lines. With LabVIEW 4, most people wrote serial com programs with a driver called serpdrv. If this file is present, then it's standard serial. If it's not, then the program may have used the inport/outport functions. If that's the case, I'm not sure what, if anything, the protmon program can do.

[sylvester]

This is the reply I got from Linear Technology:

We do not give out the source code for our demo software, mostly because
it is not intended as a reference design but more just to show off the
part quickly and easily. In the case of the DC228, the serial port is
"bit banged" to emulate an SPI interface, which is NOT the recommended
way to interface the LTC2400 to a PC in an actual application, although
it works great for a simple evaluation.

I would strongly recommend that you write your own driver, using the
timing diagrams in the datasheet as a guideline. The easiest mode to use
is shown in Figure 5 (single cycle). The only thing that it is a good
idea to add is a timeout so when you lower CS, make sure SDO goes low
within 175ms (or so - this is longer than the maximum conversion time in
both 50Hz and 60Hz rejection modes.)

Is there any example available (Labview 6.1) for this SPI programming?

[jbeale]

I also have this demo board for the LTC2400 (DC228) with a 9-pin serial port on it. The software is missing. I would like to try it, any chance I can get the demo .exe from you? Linear Tech does not have it.  -John Beale 

[goahead]

Hello everyone

I also have an old LTC2400 demo board with serial interface, version 228A, which came without software. If anyone has the missing demo software, i would be grateful if i could get a copy of it.

Thanks a lot.

[SteveRoberts]

Resurecting an old thread:

I have the DC228A version of the LTC2400 ADC demo board and the original software which came with it from Linear Tech. I got this from Linear in 1998. It worked fine on whatever old Windows machine I had at the time. When I install the software on a WXP machine it appears to install fine. When I connect up the board to my real COM1 port and run the software, I immediately get a message box with a LabVIEW icon on it which says  "Capability not supported. LTV2400 v1.01 was stopped at node 0x1BC of subVI Out Port.vi". The software then freezes and I [X] out of it. I get this same behavior on two different WXP computers. I assume the problem is in the way WXP handles access to the COMport hardware, and the way the LabVIEW vi is trying to bit-bang the port? The original 228 software may not run at all on WXP or newer, at least.

I'd like to get the demo board running. I guess the only way to do it now is as suggested, write a new vi which does the SPI protocol as the demo board wants. Any ideas?