ADS1299: Re: DRDY signal status of ADS1299

Hi Sushant,

Thanks for the post. 

Are you using the CSB signal to enable multiple devices operation on share SPI-bus? It will be beneficial if you can scope the ADS1299 SPI bus to make sure you do not accidentally send any command to the device.

Thanks

-TC

Hello TC,

 No we aren't using the CSB signal for any other device except the ADS1299.

For the measurement, we continuously keep the PWDN B pin low.

The CSB is only made high when we are reading the data from ADS1299. Can this create any potential issue? Since there is only a single slave on the SPI bus, is it advisable to continuously pull CSB low?

Note we are using a single ADS1299 and there is no daisy chaining. 

The SCLK frequency that we are currently using is 2MHz.

Please let me know the range of frequency which can be configured for the SCLK for correct and error free operation.

As said we get the readings correctly when only SPI bus between Controller (STM32) and ADS1299 is active.

If we activate the other interfaces on the board, we are facing this issue.

It would be great if we get help on this as soon as possible. We are stuck on this issue since last two weeks and are already delayed on our schedule.

I'll try to probe the SPI bus along with DRDY, SCLK, PWDN B lines and would try to post it.

Let me know if anything else is required from my side for the speedy resolution.

Best Regards,

Sushant Rajbhar

Hi Sushant,

The CSB and PWNDB signals are all active low signals for the operation of the device. I recommend you look at the SPI bus, PDWNB, and the RESETB pins with a oscilloscope to debug your issue and making sure all signals are as expected.

If you are not using the CSB for all the devices, how do you ensure there is no contention on the SPI bus? I do not know how all the other interfaces are connected to the STM32 controller, so it is difficult for me to know what the issue is. What changes when operating the ADS1299 by itself and with other devices activated on the same SPI bus?  

The minimum SCLK frequency requirement depends on a few device parameters. Please refer to Equation 9 in the datasheet for the t_SCLK calculation and explanation.

Thanks

-TC

Hello TCT,

 I know it has been a long time since my last post. We weren't able to proceed for the testing due to the covid situation.

However we are still facing issues with ADS1299.

The ADS1299 resets and it is happens randomly.

When we turn ON the device and start the measurement, after some time (random) the ADS1299 restarts.

Due to this, the configuration registers are stored to default and hence we are not able to get correct data.

We are sure that ADS1299 is restarting after doing the following test:

We made one of the GPIO high (GPIO2) to be precise.

While the device is working, all of a sudden we get a random data. The SPS also is restored to 250SPS from 500 SPS that we have set.

Also the GPIO status goes low (measured the voltage).

As this is happening in complete random fashion, we are unable to trace the issue.

Attaching a snap of the schematic for your reference. This might help you in analysis.

Note: Earlier I had stated that the issue occurs only when other interfaces are activated. But now we are observing this issue when only ADS1299 and Controller communication is active using SPI bus.

Hi Sushant,

Thanks for the post. I hope everything is well.

It is difficult to review the attached low-resolution schematic. Can you please help to send a higher resolution schematic to the following email list [ads129x-support@list.ti.com] so we can review it?

Do you observe the same behavior on multiple boards?

Thanks

-TC