Modify Standard Filters


#1

Hi all,

I’m a biomedical engineer, I have just finished my master and I’m starting to work on ECG electrodes. I have only recently started to use both openBCI and Processing so I’m not an expert.
I’m recording the ECG with 3 leads (right arm - RA, left arm - LA- and right leg - RL) using the openBCI in differential mode: RA and LA connected to pins N and P of channel 4 and RL connected to N bias (same thing that they did here: http://eeghacker.blogspot.ie/). I included the BIAS and turned off both SRB1 and SRB2 obtaining the ECG. I used the 1-50 Hz bandpass filter and the 50 Hz notch but I want to implement and use a new filter: a 0.05-100 Hz bandpass filter. I went to the source folder of the openBCI GUI and used processing to modify the 7-13 Hz filter that I found in the EEG-Processing file.
I modified the filter as follow:

case 1:
//butter(2,[0.05 100]/(250/2));
b = new double[] {
0.638360394688113, 0.0f, -1.276720789376226, 0.0f, 0.638360394688113
};
a = new double[] {
1.0f, -0.855328851270004, -0.872714628778488, 0.315962663143011, 0.412084850786751
};
filt_txt = “Bandpass 0.05-100Hz”;
short_txt = “0.05-100 Hz”;
break;

I used matlab in order to calculate the a and b vectors.
The problem is that when I started the GUI again nothing changed and the filters was still the 7-13 Hz bandpass. Did I do something wrong? Do I need to modify anything else?
Thanks for your time.