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ADS1292R: Configure ADS1292R for EMG acquisition

Harikishore R P
Prodigy 220 points
Part Number: ADS1292R
Other Parts Discussed in Thread: ADS1292

I want to use ADS1292 for EMG acquisition. I have to monitor two muscles hence I need to use two channels (1P, 1N and 2P, 2N also a reference electrode). Since ADS1292 is for ECG application, the input pins (ELA, RL, ERA etc) are quite confusing for me. I have the ADS 1292 PDK evaluation board with me. So how do I connect the electrodes to the DB9 connector for EMG input? I figured out tapping points for these input channels across C92 and C91 by avoiding the rest of the circuitry between the IC and DB9 connector (see attachment named input channels). Are those the right places to connect the electrodes? However still I haven't found a location to connect the reference electrode or is the reference electrode mandatory?

  • 0
    TI__Guru 55062 points

    Hi Harikishore,

    Using the ADS1292 for EMG will be fine. While the datasheet uses terms for ECG when describing the input pins, keep in mind that they are simply input channels to the ADC. I would recommend connecting directly after the DB9 connector to the resistor pads R85, R73. The resistor and capacitor form an RC filter that filters out the very high frequency noise that would otherwise alias back into your measurement. 

    When you say reference electrode, are you referring to the electrode that is used to drive the body to a common-mode voltage? If yes, this can be accomplished using the RLD function of the device. If you mean common point to measure your other electrodes against, then you will want to connect the reference electrode to the negative input of your channels. 

    As EMG is not the main function for the device, I recommend looking around on the forum for other posts that may help you. 

  • 0 in reply to Alexander Smith
    Prodigy 220 points

    Thank you so much for the quick response. I appreciate the efforts from TI to help their customers.

    Few questions:

    1. Connecting electrodes to R85 and R73 would provide input to Channel 1. Similarly for Chanel 2 input, shall I connect electrodes to R71 and R63?

    2. Now that I have completed the input connection, should I ground or modify the connections to DB9 connector and the RESP MODE (channel 3)?

    3. Since I am using bipolar measurement for EMG, I assume reference electrode would serve the purpose of a bias/ground. If necessary shall I connect the reference electrode to RLD input in the DB9 connector?

    4. My idea is to use an ARM processor without using the on board DSP processor of the EVM. I figured out the Test Points for extracting digital data from the ADS1292. TP11, TP42, TP24, TP46, TP47, TP52, TP53, TP56 are the serial out pins. I believe I can connect these to any controller. Any advice on that?

    5. Also, If I want to use the on board processor, can I extract data from the TX, RX pins of the board and transfer it to HC05 for bluetooth communication? If so, can I use my custom made smartphone app to read the data processed by the DSP processor and how will I program the processor to do that? 

    Your help will be highly appreciated. 

  • 0 in reply to Harikishore R P
    TI__Guru 55062 points

    Hi Harikishore,

    My pleasure. 

    1. Yes. You will most likely want to install components of similar value to channel 1 here in order to filter the high frequency noise out of the measurement. 

    2. I don't think that will be necessary. 

    3. That is correct. Yes, pin 4. Alternatively you could use R117 after the 100k resistance. 

    4. Controllers are not my area of expertise. Make sure that the controller has enough GPIO ports depending on if you want to toggle vs. command. I recommend having CS tied to a GPIO, START & PWDN/RESET can be as well, or controlled with commands. Make sure that the controller is capable of sending DIN & SCLK pulses at the desired frequency. Alternatively, can read from DOUT. The frequency can be verified in the datasheet or the BIOFAQ post in the link below. DRDY is typically connected to a interrupt. CLK can either be internal or external (especially if you want to sync measurements to something else).

    5. I am not sure about this one. I don't see a reason that you cannot extract from the TX and RX pins but I have no example code or expertise to offer for programming the DSP. 

    https://e2e.ti.com/support/data-converters/f/73/p/772058/2855202