ADS1296R - Hardware PACE detection problem

Arun Kumar27

Other Parts Discussed in Thread: ADS1296R, MSP430BT5190, ADS1296

Hi,

I am trying to make hardware pace detection work with ADS1296R.

I am using a custom board with ADS1296R and MSP430BT5190 on it and a simulator that can produce a pacer signal of width up-to 2ms and amplitude up-to 5ms

On ADS1296R following are the register configurations

0x0F, //gpio, to make them input pins
0x09, //pace. 4th channel routed to TESTP_PACE_OUT1 (Pin E3 on ADS1296R)

I am feeding this TESTP_PACE_OUT1 to the hardware pace detection circuit. I have followed the reference design for the circuit from "TI Precision Designs: Verified Design, Hardware Pace using Slope Detection" by Tony Calabria.

When i observe GPIO4, latch is not going high.

So first of all,

How do i make sure that i am getting a PACER pulse at TESTP_PACE_OUT1 ?

When i observe this pin (E3 on ADS1296) on CRO i am seeing a noisy sine kind of wave, the same trend continues on output of differential amplifier.

What might be going wrong?

Arun

over 8 years ago

0 Brian Pisani over 8 years ago

TI__Mastermind 38745 points

Hey Arun,

To verify that the simulator is actually outputting the pacemaker pulse, you could run the ADS1296R at the highest datarate and check the data on channel 4 to see if the pacemaker pulse is present. If it is, you will likely have insight into what is going on and we can go from there.

Regards,
Brian Pisani

0 Arun Kumar27 over 8 years ago in reply to Brian Pisani

Intellectual 590 points

Hey Brian,

Thanks for the quick response, i will try that and get back.

Arun

0 Arun Kumar27 over 8 years ago in reply to Arun Kumar27

Intellectual 590 points

Hi Brian,

I obtained the data at 1K SPS, looks like i am getting the PACE signal.

Following is the plot of the data i got.

But i am not observing the same at the TESTP_PACE_OUT1.

Arun

0 Brian Pisani over 8 years ago in reply to Arun Kumar27

TI__Mastermind 38745 points

Hey Arun,

Are you able to get the signal to appear from a different channel to the PACE_OUT2 pin?

-Brian

0 Arun Kumar27 over 8 years ago in reply to Brian Pisani

Intellectual 590 points

Hi Brian,

I configured PACE register = 0x0B, collected the data on Channel 3 and plotted it in excel. I am getting the PACE pulse.
But i am seeing a noisy sine wave n PACE_OUT2. (same as PACE_OUT1)

One more observation is that, there is no effect of PACE detect buffer bit (/PD_PACE bit in PACE register) on PACE_OUT1 and PACE_OUT2 signals (i get the same wave on CRO in both cases /PD_PACE = 0 and /PD_PACE = 1)

Arun

0 Brian Pisani over 8 years ago in reply to Arun Kumar27

TI__Mastermind 38745 points

Hey Arun,

Have you set bit 4 of the CONFIG2 register? This bit controls the multiplexer between the test signal input and the pace buffer output.

Regards,
Brian Pisani

0 Arun Kumar27 over 8 years ago in reply to Brian Pisani

Intellectual 590 points

Hey Brian,

In the datasheet there is no mention of pace buffer output in the Config 2 description. Where can i find it?
But anyway I tried this, still no output at any of the PACE_OUT pins.

Arun

0 Brian Pisani over 8 years ago in reply to Arun Kumar27

TI__Mastermind 38745 points

Hey Arun,

It isn't specifically stated, unfortunately, but logically you can determine this to be the case since if the TEST_PACE_OUT pin was configured as an external test signal input, it cannot simultaneously be an output. I wish this delineation was made more specific in the datasheet. Would you mind posting your schematic and your full register settings here? I have personally gotten the pacemaker signal output functionality working several times, so this is either an issue with the setup or perhaps the chip got fried.

Regards,
Brian Pisani

0 Arun Kumar27 over 8 years ago in reply to Brian Pisani

Intellectual 590 points

Hi Brian,

It is working now!! The issue was with register configuration due to some timing problem.
I read back the register and verified the updation (including the Config2 setting you suggested), it works now.
Thanks for all the suggestion.

Regards
Arun

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ADS1296R - Hardware PACE detection problem