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ADS1198 SPI

Danish Bhat
Prodigy 100 points
Other Parts Discussed in Thread: ADS1198, ADS1298

Hey!

I have purchased a ADS1198ECG-FE development kit. I detached the MMB0 motherboard and connected the sensor board with my development board. I made the following connections to initiate an SPI transfer connection:

From the J3 connectors I have connected pins SPI_CLK, SPI_IN, SPI_OUT and SPI_CS(pin 7) to the corresponding pins on my development board. 
I provide the 5V connection via pin TP7 to the sensor board. Also my elopement board has been powered by USB connection.

I now have to transfer the ECG data from the sensor to my development board. Could you please tell me if I have made the right connections to initiate the SPI transfer or do i have to make some other connections as well..?? Also could you please provide me with some source code or API which can help me in any way.

Thanks! 

  • 0
    TI__Mastermind 38745 points
    Hey Danish,

    I am required to stress to you again that the ADS1198ECG-FE is a Performance Demonstration Kit and not a development kit. As such, it is the policy of TI employees on the Precision Data Converters Forum not to provide technical support for changes made from the release version of the EVM, whether to hardware or software. What you do with the board is up to you, but you will likely not receive support on this forum.

    All that being said, when undertaking a design such as this, I'd recommend reading the product datasheet for the ADS1198 thoroughly. This device is very configurable and it's operation tends to be rather complicated. It is important to understand the interface completely. For example, in addition to the SPI pins you have listed, you will also need to connect to the DRDY output to that the ADS1198 can signal to the processor that a conversion is ready for collection.

    If you're looking for some example code, we do not have anything that is specifically tailored to be instructional, but the source code is available for the ADS1298 EVM firmware here: www.ti.com/.../ADS1298ECGFE-PDK in the table in the "Firmware Source..." row.

    The difference between the ADS1298 and the ADS1198 is the resolution of output data. The firmware itself was developed specifically for the EVM and as such may be ill-suited for an end application, but there may be some helpful guides in there when it comes to the interface specifically. My advice would be to develop an idea for how you'd want to communicate with the device before looking at the source code. Then, once your development has begun, you can look to the EVM firmware as a reference rather than a starting point for your own code.

    Regards,
    Brian Pisani
  • 0 in reply to Brian Pisani
    Prodigy 100 points
    Hey Brian,

    I totally understand that this is a Performance Development Kit however for my own personal interest I want to connect this PDK to my development board using the J3 connector.

    I understand you mentioned that I will also have to connect DRDY output, in this case does the DRDY act as CS because on my development kit I do not have any more pins left to connect.

    Thanks.
  • 0 in reply to Danish Bhat
    TI__Mastermind 38745 points
    Danish,

    CS and DRDY are not the same. DRDY is a device output that flags the host that a conversion is ready and CS is a device input which enables the interface. A detailed discussion of interface begins on page 26 of the datasheet.

    Brian
  • 0 in reply to Brian Pisani
    Prodigy 100 points
    Hello Brian,

    I had a question regarding the ECG data that we receive from the ADS sensor. When I store the data from the ADS1198 software I get the following data types;

    Device_0_Analysis.txt
    Device_0_Codes.txt
    Device_0_Volts.txt
    Estyx History.txt

    The Device_0_Codes.txt and Device_0_Volts.txt seems to be the files containing the ECG data. How can I use the data in these files for further signal processing..??
    Also I have connected the ADS1198 sensor daughter board to my development kit and what and what kind of data should I be able to receive on my development kit via SPI..??

    -Danish
  • 0 in reply to Danish Bhat
    TI__Mastermind 38745 points
    Hey Danish,

    Since the intention of the board was just to evaluate the IC for performance, there is no way to stream data to a PC in real time in its release state. The files you mentioned are convenient ways that allow you to analyze and process data after it has been collected (using Excel, Matlab, etc).

    The timing and interface protocol specifications for the ADS1198 will be described in detail in the device's datasheet. Since it would take me several long forum posts to describe every detail of the SPI communication protocol, I suggest you read through the datasheet and post here if you have specific questions.

    Regards,
    Brian PIsani
  • 0 in reply to Brian Pisani
    Prodigy 100 points
    Hey Brian,

    In the previous forums I did mention about me using the ADS demo kit daughter board with my development kit. You said that it certainly is possible to transfer data from the daughter board to the development board using the correct pins in the J3 connecter via SPI transfer.

    If now you say that "there is no way to stream data to PC in real time in its release state" could you please explain me the reasoning for this. On the other hand,I have connected the appropriate SPI pins from J3 connector and am using the GPIO as well from my development kit.

    Regards,
    Danish
  • 0 in reply to Danish Bhat
    TI__Mastermind 38745 points
    Hey Danish,

    I believe there may be a discrepancy between what each of us defines as "streaming". In my post above, I am referring to collecting data from the device, passing it to a PC via USB or some other bus, and processing or displaying it using the PC in "real time" for an indefinite period without missing a sample in the stream of conversion data. That which I just described is impossible with the EVM firmware and software in its release state (i.e. without changes).

    The process of collecting several consecutive points of data with the EVM board and processing them with an arbitrary mircrocontroller using your own proprietary algorithm is certainly possible, but will not be supported by TI engineers. It seems as though this is what you are suggesting, but before I think I misunderstood and thought you were attempting to use the EVM software to extract data in real time using the PC. Hopefully this clarifies things.

    Regards,
    Brian Pisani