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ADS1299: EMG signal acquisition with 2 electrode pads

Chuong nguyen
Prodigy 20 points
Part Number: ADS1299

Hi everyone, i'm kinda new in EMG field, Can i collect signal from a finger with 2 electrod pads? I put them on same position of my left and right hand so that i can measure the difference between these two when i move my finger. Should i use differential input mode or single-ended? Where to connect them on board for BIAS_ELEC and REF_ELEC and what value should i write to control registers? My current ads1299 daughter board is set to factory default jumpers and some of my registers:  CONFIG1: 0x00, CONFIG2: 0xD0, CONFIG3: 0xE6. Thank you very much.

  • 0
    TI__Guru 66436 points
    Hello Chuong,

    Thanks for your interest in our ADS1299 and welcome to our forum!

    Generally, I see that EMG is measured differentially, but the placement and arrangement of electrodes depends on your specific application. Trade-offs can be made with signal gain, sampling frequency, and decimation ratio to find the right resolution and signal bandwidth for your application. Our team understands how our devices are used in biopotential applications, but we're not the field experts in the end.

    I'll leave this post open in case other community members have some advice or resources to share. One platform that I like is called "OpenBCI." This group has designed several biopotential application platforms around our devices. Everything is open source and provides some really nice examples!

    http://openbci.com/


    Best Regards,
  • 0 in reply to Ryan Andrews
    Prodigy 20 points
    Hi Ryan,
    thank you so much for your reply, i'm so sorry for not making myself clear. I put 2 electrodes on same position but different arms to measure the difference between them, i'm so confused right now about the BIAS_ELEC and REF_ELEC 'cause i only have 2 electrodes and i don't know how to connect them to the board, should i pin them to CH1+ and CH1- ? And what should i do with JP25? I tried using 1 pad as REF_ELEC and the other one to CH1+ but my signal is still not relevant to my movement. Could anyone here has done this before help me through? I'm really appreciate your answers.
  • 0 in reply to Ryan Andrews
    Expert 2915 points

    Hi Ryan,

    as you mention the openBCI projects I was asked to design a PCB based on the following schematics from openBCI

    The data sheet says to leave pin 64 (reserved) open and unconnected, while in the openBCI project this pin is connected to GND.

    This schematics is done in Designsspark and as you can see as well that the nc pins 27 and 29 are connected to an nc net while nc is nc. I have my doubt that any PCB is ever done using this Designspark project. Possible this PCB has been done in Eagle and just moved to DS. There are as well other issues which proof that this schematics would not work.

    So should pin 64 / reserved be left open like in the data sheet mentioned or connected to GND as in the openBCI project ?

    thanks and

    best wishes

    Ralph

  • 0 in reply to Ralph Deffke
    TI__Guru 66436 points
    Hi Ralph,

    Please leave pin 64 open as recommended in the device datasheet.

    Best Regards,