ADS1115 Data Rate question about ads1x15 HOT 15 CLOSED

(updated your code tags)

From the datasheet

One should expect up to 10% variation, but not a factor 2.
So what you see when you set the value to 7 is within specification of the datasheet.

However when you set the value to 4 one should expect 128 +- 13 sps.

I cannot explain it right away and will check the code to see if it has an error.

from ads1x15.

If you set the datasheet to 0 I expect you will also get ~275 sps.

IN the datasheet there is a section DUTY CYCLING FOR LOW POWER
If I understand it right the internal ADC does not lower the sampling rate but does oversampling at lower speeds.
Check if I can get that confirmed.

from ads1x15.

https://www.best-microcontroller-projects.com/ads1115.html

search Low Speed averaging
f you run the ADS1115 at low speed the internal sampling rate is not lowered, since this is how delta sigma converter operates, by oversampling. The internal oscillator is set at 1MHz, and reduced to 250kHz for the ADC clock.

So it might be that you hit upon some behavior which is the combination of CONTINUOUS mode with LOW data rate.

from ads1x15.

Code does not show strange things - just looked quickly - compared mapping of the register with page18 datasheet.
All fields seem to go to the right bits in the config register (table 9)

Can you check the effective data rate when using 3 and 5 ?
(or better the whole range? but lets start with 3 & 5)

from ads1x15.

All right, I tested it again, for the rate value 5 it gives around 244, for the rate 7 it gives 817~830 SPS, which are correct for 10% variation, I will test it for the value 3.

from ads1x15.

All right, I tested it again, for the rate value 5 it gives around 244, for the rate 7 it gives 817~830 SPS, which are correct for 10% variation, I will test it for the value 3.

For the Rate value 3 it returns 280~290 SPS.

from ads1x15.

So data rate 5 is OK and 7 is OK (we may assume that 6 will be in the middle)

4 and 3 both are too high (even higher than 5) and they are almost equal. mmmm....

from ads1x15.

For the data rate 6 it gives 450~475 SPS which is also correct taking into consideration the variation of +- 10%

from ads1x15.

Yes I checked the section too, thank you, when I set the data rate to 0 it returns around 320~340 SPS.

from ads1x15.

What kind of signal are you sampling?
If it is stable voltage it might be that the DeltaSigma converter takes less time...(just thinking out loud)

from ads1x15.

What kind of signal are you sampling? If it is stable voltage it might be that the DeltaSigma converter takes less time...(just thinking out loud)

No it is not a stable voltage, I think I may use the 860SPS and then apply a downsampling method to lower it to the wanted SPS.

from ads1x15.

Just take 4 samples at 860SPS and average them would take 5 milliseconds. and dividing by 4 is fast (shift)

from ads1x15.

I was wrong about the voltage I thought you mean the source voltage, which is normally stable, yes I will use 860SPS.

from ads1x15.

@sghirsst
Is this issue still a problem?

from ads1x15.

@RobTillaart , no the problem is solved and everything is working fine, thank you very much.

from ads1x15.