ADS7881 improved code for real-time application

Hi Tariq,

There was an earlier file post on that thread that used the DMA with the ADS7881 EVM.  You can find that example project here:

http://e2e.ti.com/support/data_converters/precision_data_converters/w/design_notes/ads7881-on-the-c6713dsk.aspx

Let us know if that helps you with your project.

Hi Tom,

Thanks for the post.

I did all the jumper settings as told but it is not working, I don't see any proper sine wave on the graph window.

I am confuse with the following statements which I copied from main.c file of the project.

/*              The following settings need to be made in the   */
/*              DSP / BIOS configuration tool:                  */
/*              If the BUSY\ interrupt polarity is High-to-Low: */
/*              - Mapping of the interrupt for the DMA channel  */
/*                selected in the configuration tool to:        */
/*                    _ADS7881_rblock_finished                  */
/*              If the BUSY\ interrupt polarity is Low-to-High  */
/*              - Mapping of the BUSY\ interrupt for the CPU to */
/*                    _DCP_readData

Looking forward for your help.

Hi Tariq,

In the CDB file for the project there are options to set the interrupt trigger mechanism - either high to low or low to high.  The 5-6K Interface board also has jumpers to 'invert' (through a single gate inverter) the BUSY signal from the ADS7881.  If high to low, the program triggers a DMA transfer otherwise it uses the CPU interrupt.

Hi Tom,

I inverted the BUSY signal from ADS7881 but it is not working.

In the project, it says Ext Int 5 has been used but Int 5 is disable and Int 8 is enable. Moreover, I don't see any DMA channel active in DSP/BIOs configuration. Thought I don't know much but these are the things I noticed.

Help me running this project.

Hi Tariq,

I'm out of the country at the moment without any access to hardware to help you debug this.  Can you verify whether or not you are actually seeing any of the control lines wiggle on P2?  Also, the 5-6K Interface board does not supply the +/-12 or the +5VA to the ADS7881EVM, The +/-12 is needed for the analog front end while the +5VA is the analog power rail of the ADS7881 - it that is missing, that could be part of the problem.

Hi Tom,

I am applying +/-12V and +5V at 5-6K Interface board as mentioned in the main.c file of the project you mentioned. These connection settings are also advised in TI document.

I didn't quite understand what you mean. Are you saying to remove connections from 5-6K board and apply them at Test Points of ADS7881 EVM ?

Hi Tariq,

Not quite - the ADS7881EVM has female sockets on the bottom of the board and male pins on the top side.  These actually 'feed through' the evaluation board, so the chip select, the CONVST, the /RD etc. control lines can be probed on the top side of the EVM stack-up.  You should be able to see the CONVST pulsing and then verify that the BUSY signal goes active (BUSY is the DSPs interrupt source) to see if the DSP is actually responding.

Tom,

My Processor got some problem :(.. I will get back to you ASAP.

Thanks.