LDC1000: Trouble adjusting sample rate in LabVIEW

Hi Bala,

Sorry, I have accidentally marked your answer as having answered my question

To clarify, I am integrating this sensor into a larger system powered by LabView, so LabView related files are what I'm interested in. I am not sure if this was obvious from your response.

To be sure, I have uninstalled everything LDC1000 related and downloaded the following from the LDC1000 page.

• Sensing Solutions EVM GUI Tool v1.9.4 (Rev. E)
  • This is the same version you linked me to in your previous email. I have replaced it with the one downloaded through your link, just in case. 
  • The GUI appears to have been made using Python.
  • I have checked the default install directory (C:\ti\Sensing Solutions EVM GUI-1.9.4) and am unable to find any LabView files.
• LDC1000 Firmware Library for the MSP430
  • None of the firmware files here are suitable for the MSP430 chip on the LDC1000 board (Physically marked as MSP430F5528)
  • Discarded

• LDC1000 EVM Software GUI (not recommended)
  • This has installed two programs - Sensing Solutions EVM GUI Tool v1.9.3 and LDC1000 EVM GUI 1.0.4.1
  • Sensing Solutions EVM GUI Tool v1.9.3 is an older version of the GUI you sent me the link to - I have ignored this
  • I believe LDC1000 EVM GUI 1.0.4.1 is the GUI you alluded to that is no longer supported. This appears to have been made using LabView (Visual cues). It has an option to change the sample rate. My desired sample rate of 1Hz works when set through here.
  • This software also comes with LDC1000 Firmware 0x300 (Default directory is C:\Program Files (x86)\Texas Instruments LDC1000 EVM GUI\Firmware\LDC1000_F5528_V3_Public). I have queried my LDC1000EVM board and it claims to have this version installed. Comparing expected vs actual responses to commands sent through a terminal affirms this.
  A "LabView" folder can be found in the default install directory (C:\Program Files (x86)\Texas Instruments LDC1000 EVM GUI\LabView). This contains the only LabView source files I can find published by TI on the LDC1000EVM product page and forum.
  • The LabView project contained within is not the same as that used to make LDC1000 EVM GUI 1.0.4.1.
  • Readme file comments: "This folder contains LABVIEW Vis to read/write registers and to stream data from LDC1000EVM. Please see "LDC1000 Demo.vi" for typical usage of these Vis"
  • 'LDC1000 Demo.vi' is what I have used to build on.

I believe, therefore, despite they fact the LabView files were supplied with the old, no longer supported GUI, that I have the most up to date (and only) LabView files that have ever been published TI, found here: http://www.ti.com/lit/zip/snac058

As I am able to do exactly what I want in LDC1000 EVM GUI 1.0.4.1, which appears to have been made using LabView, would it be possible to get the source files for it, and see how it has been done there?

EDIT - Looking a little more closely at the firmware and LabView code, it appears that the "08" command is being sent to the MSP430, where it is then processed by the functions in "host_legacy.c". I am confused about what this function actually does, because I am reading and seeing conflicting information... I'll explain. Let's use 5,000Hz for this example.

    case Command_Timer_Interval:
    	data_word = (uint16_t) hexchar2dec(&pBuf[2],4);
		data_word = (24e+6)/data_word;
		taskInterval = data_word/SCHEDULER_DIV;
		pBuf[8] = (data_word >> 8) & 0xFF;
		pBuf[9] = data_word & 0xFF;
		host_response = 1;
		break;

In LabView, there is a numerical input box labelled "Sample Frequency (Hz)". The value put in there is converted to hex and prefixed with "08". The hex value for 5,000 is 0x1388 Therefore, the output command from Labview is 0x08138800. Command_Timer_Interval is defined as 08 in the header, so the code above should run. SCHEDULER_DIV is defined as 240 elsewhere. taskInterval, therefore, equals 20. This is then saved with the task, and defines the number of ticks before it is actioned. "scheduler.c" has a comment defining 1 tick = 100us. This will result in a read every 2000us = 0.002 seconds = 500Hz, not 5,000. If for arguments sake, I have am off by a factor of 10 because I missed a division or multiplication somewhere, then to have a frequency of 1Hz, my tick value, and therefore, taskInterval, would need to be 10,000. Working backwards:

taskInterval = data_word/SCHEDULER_DIV;

Therefore, data_word = 10,000*240 = 2,400,000. 

This is not possible since data_word is defined as a 16-bit integer (Max value of 65,535)

Then in this thread, https://e2e.ti.com/support/sensors/f/1023/t/295036, however, under question 37: "send data length = 4 numeric ASCII chars.  Timer clock period. (e.g. "1234" = 24MHz/1234 = 19.4kHz )".

Then the MATLAB code provided with the old GUI has this formula: 

d=fread(sport,c);
T=256*d(9)+d(10);
Fset=24e6/T;

I would be very appreciative if I could take a look at the LabView files that were used to make the LDC1000 EVM GUI 1.0.4.1 and see how 1Hz sampling was done there.

Thanks again

Hi Ali,
Right now, we only support applications and hardware question related to LDC1000. Sorry I do not have the source code that you're requesting.

Best Regards,
Bala Ravi