Ecg analog out from Cyton
I needed an analog output from the Cyton board for further processing of the amplified raw ECG signal.
I see from the block diagram of the ADS1299 that there a single place where the output of each channel are summed and connected to the BIAS_INV pin.
If I tap an output from BIAS_INV would it give me a correct representation of the ECG signal.
I plan to use only a single differential channel. IN1P and IN1N.
Comments
The Bias pin / function on ADS1299 is equivalent to Ground pin on other amplifiers. However it adds an additional feature of rejecting mains noise. It does this by injecting an 180 degree out of phase copy of the mains artifact. Another name for this in ECG applications is RLD / DRL Right Leg Drive.
https://www.google.com/search?q=RLD+Right+Leg+Drive
https://en.wikipedia.org/wiki/Driven_right_leg_circuit
So in general you cannot access internal functions inside the ADS1299. I'm unclear why you would want to do this. You have a high fidelity sample stream at your chosen gain factor. Since ECG is in the millivolt range rather than the microvolt range of EEG, you have plenty of signal to noise ratio.
William
In addition to the DSP functions in Brainflow, there are a plethora of DSP libraries available in every conceivable computer language.
https://www.google.com/search?q=python+dsp+library
https://brainflow.readthedocs.io/en/stable/Examples.html#python