ADS1115: continuous conversion mode

Denis Rakoto

Other Parts Discussed in Thread: ADS1115, ADS1118

HI,

We have an FPGA as I2C Master interface to the ADS1115 device. We would like to configure the device with 2 single-ended or 2 differential inputs.

Is it possible to switch the Input multiplexer live between two conversions if the device is configured in "continuous conversion" mode?

using with the following sequence:

1) Configure AIN_0, read dummy data when ALERT/RDY asserted

2) Configure AIN_2, read data from AIN_0 when ALERT/RDY asserted

3) Configure AIN_0, read data from AIN_2 when ALERT/RDY asserted

4) goto 2)

From our test, it looks like the device keeps providing converted data from only one of the 2 inputs, AIN_0 or AIN_2.

Note: I found a thread with somebody asking a similar question for the ADS1118 but I couldn't see the confirmation for the "continuous conversion" mode.

Thanks,

Denis

over 8 years ago

0 Krunal Maniar over 8 years ago

TI__Intellectual 1610 points

Hello Denis,

Yes, it is possible to switch the input channel setting in continuous conversion mode and you are correct, the device will keep converting data and give out a conversion result even while switching channels. However, to maximize the throughput, I would recommend you to run the device in single-shot mode.

To elaborate single-shot mode and continuous conversion mode while multiplexing between channels, I would like to refer you to a couple of forum posts:

https://e2e.ti.com/support/data_converters/precision_data_converters/int-precision_data_converters/f/75/p/313781/1092074#1092074

https://e2e.ti.com/support/data_converters/precision_data_converters/f/73/p/526236/1916483#1916483

Please let me know if you need further explanation.

Thanks,

Krunal

0 Denis Rakoto over 8 years ago in reply to Krunal Maniar

Prodigy 40 points

Hi Krunal,

Thanks for the clarification.

I was able to read the second post that you are referring to. But for some reason, I'm getting the following message when trying to open the first link:

Access Denied

You do not have permission to view/download this item.

Thanks,
Denis

0 Denis Rakoto over 8 years ago in reply to Denis Rakoto

Prodigy 40 points

Hi Krunal,

Few more questions:

Is this a valid configuration?

MODE: '1' power-down single-shot mode
COMP_POL: '1' Active high
COMP_QUE: '00' Assert RDY after one conversion

with the ALERT/RDY pin set to conversion ready pin via the Hi_threshold and Lo_threshold registers setting.

In other word, will I still be able to see RDY at the end of conversion if the device is configured in "single-shot" mode?
My understanding, the device starts converting after a successful ACK of the second byte of the Config register write.

Thanks,
Denis

0 Krunal Maniar over 8 years ago in reply to Denis Rakoto

TI__Intellectual 1610 points

Hello Denis,

You are right, you will be able to see RDY at the end of each conversion. I would also like to mention that OS (Bit 15) starts the conversion in single-shot mode. I just had another forum question for which I had to explain the sequencing in single-shot mode. Please check the below link:

e2e.ti.com/.../2017139

Thanks,
Krunal

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ADS1115: continuous conversion mode