Problems of getting respiration and ECG data from ADS1292R

Yiwen Meng

Other Parts Discussed in Thread: ADS1292R, ADS1292

Hello,

I'm getting respiration and ECG signal using ADS1292R at 250SPS but I found the result is kind of strange as you can see the attached plots. For the respiration signal, it only got the correct data at the first four respiration cycles and then went flat. For ECG signal, the R peak was attenuated while the T peak was amplified. Therefore, please let me know if anyone has encountered this problem before and what changes I need to make.

Here is the set up code for ADS1292R:

void setup_ADS1292 ()
{
send_command(SDATAC);
write_byte(CONFIG1, 0x01);// 250sps

write_byte(CONFIG2, 0xA0);

write_byte(CH1SET, 0x40); // gain 4 for channel 1

write_byte(CH2SET, 0x00);

write_byte(RESP1, 0xF2); // 135 phase

write_byte(RESP2, 0x03);

send_command(RDATAC);
digitalWrite(PIN_START, HIGH);
send_command(START);
}

Thanks,

Yiwen

over 8 years ago

0 Tom Hendrick over 8 years ago

TI__Guru**** 181001 points

Hi Yiwen,

Can you post your ADS1292R schematic? Use the 'Use rich formatting' option and attach your file there.

0 Yiwen Meng over 8 years ago in reply to Tom Hendrick

Intellectual 500 points

Hello Tom,

The schematic I was using is Figure 56 in page 58 of ADS1292R datasheet and I just noticed that I actually got the respiration signal when I zoomed in the flat part on the respiration plot above, which was like the other figure below, so do you is there way to amplify only the AC part of the signal? Besides, Is there anything I need to change of setting up registers?

Thanks,

Yiwen

0 Yiwen Meng over 8 years ago in reply to Tom Hendrick

Intellectual 500 points

It seems like attaching the figures was not successful, so I'm attaching them here.

0 Yiwen Meng over 8 years ago in reply to Tom Hendrick

Intellectual 500 points

Hi Tom,

Could you please tell me how to resolve this issue?

Thanks,

Yiwen

0 Tom Hendrick over 8 years ago in reply to Yiwen Meng

TI__Guru**** 181001 points

Hi Yiwen,

It looks like it is taking quite a while for your RESP signal to settle. Are you using a proper PCB or is your setup a blue wired proto board? You can also review this application note which might help: www.ti.com/.../sbaa181.pdf

0 Yiwen Meng over 8 years ago in reply to Tom Hendrick

Intellectual 500 points

Hi Tom,

I'm using jumper wire and breadboard for connection. I also noticed that it usually takes 15 seconds for respiration signal to settle and I have double checked connection so I doubt if my register setting is correct. Also I attach 47nF cap between PGA1N and PGA1P according to the note on page 61 of the datasheet.

Thanks,

Yiwen

0 Tom Hendrick over 8 years ago in reply to Yiwen Meng

TI__Guru**** 181001 points

Hi Yiwen,

The jumper wire and bread-board connections can be a large part of your problem. Do you expect to be making a proper PCB to continue your evaluations?

0 Yiwen Meng over 8 years ago in reply to Tom Hendrick

Intellectual 500 points

Hi Tom,

Yes, right now I'm using bread board to make sure my set up can get the correct signals and later on changing to PCB, so can you confirm that all the register setting shown before are correct?

Thanks,
Yiwen

0 Tom Hendrick over 8 years ago in reply to Yiwen Meng

TI__Guru**** 181001 points

Hi Yiwen,

I don't see anything wrong with your register settings. If you are using 'dry' contacts, you can try adding a little gel which may help settle things a little faster.

0 Yiwen Meng over 8 years ago in reply to Tom Hendrick

Intellectual 500 points

Hello Tom,

Thanks for your suggestion! And do you think the wire connection is also the reason why R peak of ECG signal is attenuated (shown in figure of ECG signal)? The fact is I do not see this type of attenuation when I powered down channel 1 (respiration signal) and remained all the connection, but I got the attenuated signal after I set channel 1 to get respiration signal and channel 2 to get ECG signal. That's why I thought the register setting may cause this problem. Do you think so?

Thanks,

Yiwen

0 Tom Hendrick over 8 years ago in reply to Yiwen Meng

TI__Guru**** 181001 points

Hi Yiwen,

Let see if getting the code cleared up on the other post helps resolve this one...

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Problems of getting respiration and ECG data from ADS1292R