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ADS1292R starting questions

HECTOR
Intellectual 865 points
Other Parts Discussed in Thread: ADS1292R, ADS1292, ADS1292ECG-FE

Hello All ;

 

I am happy to join TI forum ; I am digital engineer I have good analog background ; We would like to design an AED using ADS1292R ( good chip) ; Since ECG signal are a bit complicated for me ; I have some questions before getting in the design .

  1. Do I need to use amplifiers to amplify ECG signal before ADS1292r? If yes ; do you suggest cisruits or application notes?
  2. My design will be one lead ecg ; only two electrodes; so how can i use pseudo RLD with ADS1292R ?
  3. In the kit of ADS1292R ; there are 3 digital filters impelmented ; IIR, FIR and notch ; where I can find the codes of these filters ?

 

I looking to get helped and guided in the forum ;

 

Thank you in advanced .

Hector

  • 0
    TI__Mastermind 43915 points

    Hi Sami,

    I will do my best to help answer your questions in red-

    1. Do I need to use amplifiers to amplify ECG signal before ADS1292r? If yes ; do you suggest cisruits or application notes? Measuring ECG signals can be accomplished directly with the ADS1292 or ADS1292r without a need for an external amplifier. Adding an external amplifier is going to add noise to an, already, noise sensitive system.
    2. My design will be one lead ecg ; only two electrodes; so how can i use pseudo RLD with ADS1292R ? One way is to AC couple the inputs and then use either the RLD or midpoint between the two power supplies to set the bias point at the the input pins using weak pull up resisters. As shown below  

    1. In the kit of ADS1292R ; there are 3 digital filters impelmented ; IIR, FIR and notch ; where I can find the codes of these filters ?  Depending on what you are interested in, the filtering was either done in the MSP430 firmware or in labview. The firmware has the filtering that is used during LIVE ECG Display which shows the ''streaming'' data in the GUI. The MSP430 firmware is found here:  C:\Program Files\Texas Instruments\ADS1x9xevm\Firmware. The Analysis tab uses filtering that is done in labview. If you are interested in that source code, let me know and I can get it to you.


     Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Intellectual 865 points

    Thank you Tony ;

    I will tell you the results during my development;

    I will use l bipolar power supplies ; so i will tie them to 0 volt (Avss  middle point) that what i understand from your post , Am I right?

     

    Do I need in this case a low pass filter two after the AC couple ?

    I dont have that link in my pc ; where do i install them kit softwares?

     

    Regards

    Hector

     

  • 0 in reply to HECTOR
    TI__Mastermind 43915 points

    Hector,

    Software and details on the EVM board can be found here -

    http://www.ti.com/tool/ads1292ecg-fe

    In the User's Guide, you can see the schematic to show an example of how we designed around the part. You will want a RC anti-aliasing filter at the front end as well as patient protection circuitry.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Intellectual 865 points

     If you are interested in that source code, let me know and I can get it to you.

     

    Hi  Tony

    Yes please ; could you give the source code ?

     

     

    Regards

    Hector

  • 0 in reply to HECTOR
    Intellectual 865 points

    Hello

    T o the analog guys ; Please check my first prototype shematic with ADS1292R and let me know please if i have something wrong .

    I use channal 2 for reading ECG  ; because channal one will be used for respiration .

    I use RLDout with 10M ohms resistor directly to the ECG signals ; because I use only 2 electrodes reading .

    I use 22.2k ohms ,  with 6.8nF to forum a lowpass filter of cuttoff frequency about 1kHz for anti- aliasing ; my sample frequency will be maximum 500SPS.

    I use +5v/-5v for ADS1292R and 3.3v for digital . 

    I use internal oscillator.

    I leave the unused pins floated.

    I hope you could guide me to add pace detection to this circuit.

    Thank you in advance.

     

     1423.ECG_MODULE_R_1.0.PDF

     

     

  • 0 in reply to HECTOR
    TI__Mastermind 43915 points

    Hector,

    The source code is located in the following path once you download the ADS1x9xECG-FE software here -

    http://www.ti.com/tool/ads1292ecg-fe

    Source code will be installed here -

    C:\Program Files\Texas Instruments\ADS1x9xevm\Firmware

    All other source code for labview, etc. can be found here -

    ftp://ftp.ti.com/pub/data_acquisition/ECG_FE/ADS1292/

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Intellectual 865 points

    Thank you alot ;

    I would be happy if someone could guide me to get good pace detector circuit too ; I? have googled around but nothing ...

     

    Regards

    Hector

  • 0 in reply to HECTOR
    TI__Mastermind 43915 points

    Hi Hector,

    We are in the process of doing some testing on a hardware pace detection circuit to be used with the ADS129x family of devices. Check back or post here again in about two weeks to give us time to complete testing and I can let you know how it turned out as well answer any questions you may have.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Prodigy 70 points

    Hello all,

    Started to use the ADS1292R but I am not sure about what power supply is needed to make run the respiration and EKG funtionalities properly. The datasheet says that two are needed, an analog one and a digital one,can they be the same power supply?,so they  have the same value (3.3V)?, My analog signals won't go over 3.3 V and my Uc runs with 3.3 V as well.

    Thanks in advance!

  • 0 in reply to Tony Calabria
    Prodigy 70 points

    Thanks, i will connect the analog and digital voltage pins to the same power supply of 3.3 V then.

  • 0 in reply to japex92
    Intellectual 865 points

    I would use bipolar supplies +5/-5 ; do you suggest me to use a unipolar 0-3.3v?

     

    Jario could you share your shematic? Or could you check my shematci please ?

     

    Regards

  • 0 in reply to HECTOR
    Prodigy 70 points

    Hector,

    It really depends on circuit design and the components you are working with. I dont really use 5/-5 supplies anymore as they considered by some literature authors as obsolete; because they need to be referenced to dc level when passing through a Uc, but it is up to you.

    I highly recommend to use unipolar ones.

    Regarding the schematic I am using the "ADS1x9xECG.pdf" file, page 51. http://www.ti.com/lit/ug/slau384a/slau384a.pdf

    or if you insist with bipolar,  on page 60 of the "ads1292r.pdf" file there is a good option.  http://www.ti.com/lit/ds/symlink/ads1292r.pdf

    Don't forget to set the internal reference  by setting the CONFIG2 register.

    Cheers,

  • 0 in reply to Tony Calabria
    Intellectual 865 points

    Hi Tony

    Any progress  about the pace detector cırcuit?

     

    Thank you

  • 0 in reply to HECTOR
    TI__Mastermind 43915 points

    Hector,

    In the testing process.

    Will get back to you once completed.

    Regards,

    Tony Calabria

  • 0 in reply to Tony Calabria
    Prodigy 70 points

    Hello Tony,

    I have been through some documents and software routines to program the ADS but have not been able to do properly. I changed my mind and decided to place only sources and test the communcation. Will the coponent work with just the hardware involved in the attached file?

    Thanks!

  • 0 in reply to Tony Calabria
    Intellectual 415 points

    Dear Tony Calabria,

     Ads1292R has 3 pins(RLDINV, RLDOUT and RLDIN) for RLD. Where should i connect midpoint of resistors you suggested above? And What Should I do with other Pins of RLD

    Regards,

    Jaydeep Panchal

  • 0 in reply to jaydeep Panchal
    TI__Guru 66206 points

    Hi Jaydeep,

    The midpoint of the resistor divider would connect to the input of the ADS1292. This would set the DC voltage at the input to midsupply with a pull-up to AVDD and a pull-down to AVSS. In this case, you won't need the RLD amplifier and it can be powered-down. RLDINV and RLDIN can be left floating.

    Alternatively, you could use the RLD output (RLDOUT) and use a single pull-up resistor between RLDOUT and the input node, as shown below. See the device datasheet for use of the RLDIN and RLDINV pins.

    Best Regards,

  • 0 in reply to Ryan Andrews
    Intellectual 415 points

    hi ryan,

    Thank you for reply. i have only two electrodes for ECG measurement. Is Following right For RLD connection?

    regards,

    Jaydeep

  • 0 in reply to jaydeep Panchal
    TI__Guru 66206 points
    Hi Jaydeep,

    You still need to close the loop around the RLD amplifier. This is done by connecting RLDOUT to RLDINV. Using a parallel RC combination as shown in Figure 47, you can low-pass filter the output noise of this amplifier. Remember to select the internal RLDREF voltage (AVDD+AVSS)/2 by setting RESP2[1] = 1.

    After configuring the RLD amplifier, you can connect a high-impedance pull-up resistor to RLDOUT as shown in your schematic (R9 and R10). You will not need to install R1, R2, R3, or R4.

    Best Regards,
  • 0 in reply to Ryan Andrews
    Intellectual 415 points

    Thank you Bro...

    :-)

  • 0 in reply to Ryan Andrews
    Intellectual 415 points

    Dear Ryan Andrews,

    Brother, Can you please review the connection of ADS1292R in attached file.

    Regards,

    Jaydeep Panchal

    8475.ADS1292R.pdf