ADS1115: ADS1115 read data issue

Sriram S

Other Parts Discussed in Thread: ADS1115

Hi,

We are using an ADS1115 to read 4 single-ended channels using single-shot conversion mode. It works fine for a while, but after some time, we encounter an issue where the ADS1115 no longer provides correct readings.

This same issue occurs across multiple ADS1115 devices on different PCBs.

For example, I set a voltage of 3.6V using a variable power supply and measure the output using both a multimeter and the ADS1115. Initially, both readings are accurate. However, after about 10 minutes, the readings from the ADS1115 become incorrect.

issue -1. In one case, the multimeter still measures 3.6V, but the ADS1115 shows 6.143V.

issue -2. After 10 minutes, if I increase the power supply voltage from 3.6V to 4V, the multimeter correctly shows 4V, but the ADS1115 still shows 3.6V.

It appears that the ADS1115 is either hanging or freezing after running for some time.

5 months ago

0 Angel Rodriguez de San Miguel Bermudez 5 months ago

TI__Expert 8130 points

Hi Sriram,

What is the configuration register settings being used for your measurements?

How are you capturing the ADC's readings?

Can you probe the digital communication lines to the ADC with a logic analyzer when the ADC readings become incorrect? It is possible that this is an issue with the microcontroller/code rather than the ADC. This will help verify what the ADC is actually communicating.

Best Regards,

Angel

0 Sriram S 5 months ago in reply to Angel Rodriguez de San Miguel Bermudez

Prodigy 240 points

Hi Angel,

The configuration register (Figure 8-5. Config Register — ADS1115) is set as follows:

Channel 0 = 0xC183
Channel 1 = 0xD183
Channel 2 = 0xE183
Channel 3 = 0xF183

I will capture the ADC readings using a microcontroller. Additionally, I will use another slave device on the same I²C bus, but that slave is functioning correctly.

0 Angel Rodriguez de San Miguel Bermudez 5 months ago in reply to Sriram S

TI__Expert 8130 points

Hi Sriram,

Your configuration register settings look correct.

Can you probe the digital communication lines when the ADC's readings become incorrect after some time? This will help verify if the ADC is actually reporting back incorrect conversion data, or if there is something else going on in the digital communication/controller side that causes this.

Angel

0 Sriram S 5 months ago in reply to Angel Rodriguez de San Miguel Bermudez

Prodigy 240 points

Hi Angel,

If any status register is available for data response and an extra ACK is sent from the microcontroller to the ADS1115, will it affect the ADS1115?

Is there any provision available to reset the ADS1115?

Sriram S

0 Bryan Lizon86 5 months ago in reply to Sriram S

TI__Guru 52586 points

Hi Sriram S,

Angel is out of the office today, he will get back to you in the next 1-2 days

-Bryan

0 Angel Rodriguez de San Miguel Bermudez 5 months ago in reply to Sriram S

TI__Expert 8130 points

Hi Sriram,

Figure 7-9 in the data sheet shows how to read from the device through I2C. Is an extra ACK being sent from the microcontroller that is affecting communication to the device? Please verify that your digital communication complies with what is stated in the data sheet:

Sriram S said:
Is there any provision available to reset the ADS1115?

You can reset the device by power-cycling it or by performing an I2C general-call reset command. When the ADS1115 receives a general call reset command (06h), an internal reset is performed as if the device is powered up.

Best Regard,

Angel

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ADS1115: ADS1115 read data issue