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ADS1198: Receive continuous large length data over DMA

Lolo Pidi
Prodigy 40 points
Part Number: ADS1198
Other Parts Discussed in Thread: ADS1194

Tool/software:

I am using the ADS1198 with DMA. I configured the chip in RDATAC mode and am able to get data frames of 19 bytes.

Now I want to read multiple frames at once so that I can process larger chunks of data without involving the CPU for each small 19-byte frame. How can I configure the chip to read multiple frames at once? I tried increasing the buffer and DMA length, but I get an interrupt on the DRDY pin before the SPI transaction is complete, and I am unable to make it work.

For 19 bytes, the SPI DMA configuration works well.

  • +1
    TI__Guru 62196 points

    Hi Lolo,

    Thank you for your post.

    The ADS1198 does not have an internal FIFO. Therefore, it is not possible to read multiple conversion results in a single DMA transaction.

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 40 points

    Thank you for the quick reply.

    I was going through the datasheet and in the Data Retrieval section, I found the following part. Does this relate to multiple data read over DMA in a single transaction or something else? From what I understand, DAISY_EN should be used when multiple ADS1198 devices are connected, allowing simultaneous retrieval of conversion data from all of them.

    The ADS1194/6/8 also provide a multiple readback feature. The data can be read out multiple times by simply giving more SCLKs, in which case the MSB data byte repeats after reading the last byte. The DAISY_EN bit in CONFIG1 register must be set to '1' for multiple readbacks.

  • 0 in reply to Lolo Pidi
    TI__Guru 62196 points

    Hi Lolo,

    No, this feature does not refer to reading multiple conversion results at one time. Rather, it means that the same conversion result can be read more than once by sending extra SCLKs (i.e. extending the SPI frame length).

    Regards,

    Ryan

  • 0 in reply to Ryan Andrews
    Prodigy 40 points

    Thank you for the clarification.