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ADS1299: Signal outlier is showing even internal test signal and I didn't have any output when electrodes are attached to skin(muscle).

woochang jung1
Prodigy 30 points
Part Number: ADS1299

Hello, all.

I am implementing 8-Ch EMG system based on ADS1299 (Arduino UNO is used as MCU).

I have 2 problems:

1. Signal outlier is showing on every setting  even internal test signal.

When I check the internal test signal, registers setting:

CONFIG1 = 0x96

CONFIG2 = 0xD0

CONFIG3 = 0xE0

CHnSET (All channals) = 0x05 (not floating, connected to AVDD)

And checked values (VCAP checked with closest capaciter):

VCAP1 = 1.19V 

VCAP2 = 2.5V

VCAP3 = 6.87V

VCAP4 = 2.27V

VREF = 4.48V

2. I didn't have any output when electrodes are attached to skin(muscle).

When I check electrode signals, I focused on only Ch-1.

My setting: 

CONFIG1 = 0x96

CONFIG2 = 0xC0

CONFIG3 = 0xE0

CH1SET = 0x30 (I checked every gain)

CHnSET(Ch-2~8) = 0x81 (not floating, connected to AVDD)

And checked values (VCAP checked with closest capaciter):

VCAP1 = 1.19V 

VCAP2 = 2.5V

VCAP3 = 6.87V

VCAP4 = 2.27V

VREF = 4.48V

My signal was showed that:

I have ADS1299EEGFE-PDK. Using this domo kit and in the same electrodes and behavior, signal was showed that:

I don't know why didn't make any signal without noise. I checked internal test signal, VCAP1~4, VREF, and Device ID(it is 111110, same whith ADS1299EEGFE-PDK).

How can I fix these problems?

Thank you.

Best regards,

Woochang Jung

  • 0
    TI__Guru 55312 points

    Hi Woochang,

    If you have not done so already, please confirm that your code to voltage equation is correct using the BIOFAQ: https://e2e.ti.com/support/data-converters/f/73/p/772058/2855202

    Second, I would start investigating the communication between the ADS1299 and the Arduino. There very well may be a timing misalignment, that leads to sometimes having a sample truncated - which leads to erroneous readings. Unfortunately I cannot help you debug an issue with an Arduino since it is not a TI product. However, I would start with using an oscilloscope to measure the relevant SPI communication signals - see the BIOFAQ. 

    Using the oscilloscope readings, checking what is actually received by the Arduino, and then verifying that the result is graphed correctly should help you identify where the issue is.