OPT3101: Got barely no signal output while using Dealias Mode.

Li Jiayu

Other Parts Discussed in Thread: OPT3101

Hi everyone,

Recently, I tried configuring the OPT3101 sensor into Dealias Mode for long-distance measurements. However, I'm encountering an issue where the output signal on the LED pin is extremely weak — it's only detectable up to about 10 cm , which is way below the expected performance.

I've configured all the registers according to the official TI Dealias mode documentation , and also referred to community solutions such as this one (https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1345290/opt3101-dealias-mode) . Unfortunately, none of these suggestions resolved the issue.

Out of curiosity, I tried disabling the sequencer mode , so that the device doesn't automatically switch frequencies. That’s when I started getting a normal signal output. However, this approach obviously doesn’t run in Dealias Mode , so it's not a real solution.

So now I’m wondering:

Is there a way to manually switch between frequencies in Dealias Mode instead of relying on the sequencer?
Or can I configure the sequencer to switch more slowly between frequency steps?
Are there any other known issues or configuration tips related to enabling Dealias Mode successfully?

Any advice or insights would be greatly appreciated!

Thanks in advance!

6 months ago

0 Li Jiayu 6 months ago

Prodigy 10 points

For more informations, calib process went out just fine following the guidence of official document. Everything went wrong after starting the sequencer mode. I found an unanswered post on TI chinese supporting bbs (https://e2echina.ti.com/support/sensors/f/sensors-forum/286532/opt3101-sdk-opt3101-sdk) with similar issue. It seems a long last problem and it really confused me why no solution could be found.....

0 Daniel Balmaceda 6 months ago in reply to Li Jiayu

TI__Expert 4420 points

Hi Li,

Our apps engineer for the OPT3101 is currently out of office. Apologies for the delay in response.

Thanks,
Daniel

0 Li Jiayu 6 months ago

Prodigy 10 points

I'm still waiting for the answer... I noticed that problem disappeared when I stopped reading from the DEALIAS_BIN register. I think it means there's something wrong with the dealias-mode. Hopping for response.

0 Joseph Scherphorn 6 months ago in reply to Li Jiayu

TI__Expert 5240 points

Hello Li,

You say the "output on the LED pin is extremely weak" --How have you determined this? Do you mean the current is lower than expected or simply that the illuminance provided by the led is weaker than expected?

Are ere you doing this testing on custom board or one of our TI EVM boards?

Thank you,

Joseph Scherphorn

0 Li Jiayu 6 months ago in reply to Joseph Scherphorn

Prodigy 10 points

Since I don't have access to a custom board, I only tested the functionality on my own designed board. I conducted a simple comparison of the LED amplitude output between normal mode and de-alias mode, and found that there was virtually no output when using de-alias mode.

Further testing revealed that the issue stemmed from reading the DEALIAS_BIN register. For unknown reasons, accessing this register caused unexpected behavior in the system.

0 Joseph Scherphorn 6 months ago in reply to Li Jiayu

TI__Expert 5240 points

Hello Li,

Ensure you are using the 8.57MHz freq.(dealias_frequency = 0)

NCR_CONFIG = 0

The below post has details on correct calculation of the timing register values:

(+) [FAQ] OPT3101: Dealias Operation - Sensors forum - Sensors - TI E2E support forums

additionally ensure you are computing the crosstalk scaling coefficients with measured data from both frequencies.

0 Li Jiayu 6 months ago in reply to Joseph Scherphorn

Prodigy 10 points

Things were configured as you suggested. I had done the coefficients and set the registers, it didn't work.

0 Joseph Scherphorn 6 months ago in reply to Li Jiayu

TI__Expert 5240 points

Hey Li,

Thanks for the info. Please provide your sequencer code, register settings, layout, and the part numbers you are using for emitter and diode

Thank you,

Joseph Scherphorn

0 Joseph Scherphorn 5 months ago in reply to Joseph Scherphorn

TI__Expert 5240 points

Hi Li,

Was waiting on sequencer code. Since some time has passed, marking this closed for now - please let us know if further help needed

Best,

Alex