VL53L4CX long series of bad measures

[ChristopheG]

Hi, I'm testing some VL53L4CX for about 10 months with nrf52832 using I2C. It's used in very dark conditions and within 3m and I take 15 measures 24 times a day.

Between periods of measures I completely power off the sensor with an LDO.

It works fine for long period (1 month or more) and sometimes it starts a long period of consecutive bad measures.

(15 measures with status <> 0). It can last more than one week and it comes back to normal for several weeks...

I used the example of SimpleRanging code in app_tof.c only adapted for nrf52:

- power on + I2C_Init + MX_TOF_Init + MX_TOF_Process + MX_TOF_DeInit + I2C_DeInit + power off

More than once, I just put the device in ambient light and it resumed the correct measurements...

Questions:

- How is it possible that it seems to stay in bad configuration despite of powering off the sensor?

- Is it a way to reset to factory values when I have bad measurement?

Thanks for your answers.

[Zhiyuan.Han]

Hi Christophe

Normally even though you let L4 enter unknow states with ESD/EMI or other noise, in theory L4 will reboot totally with power reset, and then you will let L4 recover back to normal.

From your description, your issue is strange, have your checked I2C with oscilloscope? or may I know your L4 schematic? anyohter device sharing same I2C bus with L4?

Do you have other device emitting IR light working at same time with L4?

br

Zhiyuan.Han

[ChristopheG]

Hi Zhiyuan.Han, thanks a lot for your answer.

here is the schematic of the L4:

There isn't any other sensor on this I2C bus, and no other IR light on this device. The VDD_SR entry coming from LDO is dedicated to the L4. 

We have checked TP20 to TP23 point with oscilloscope and there is no voltage between the periods of measures... 

Regards,

Christophe

[Zhiyuan.Han]

Hi Christophe,

Thanks for sharing schematic, seems no issue on the connection, and you shared no other noise, very strange.

Normally we will use power reset to reset the device totally. what I can sugget are:

1. Can you try power off the LDO, and wait a bit longer time before power on the LDO, I guess maybe the power supply form LDO was not drop to 0 before your re-enable the LDO supply.
2. The other suggestion is can you try attached I2C test code when you see the issue happen? just to make sure I2C is working fine when issue happen.

Br

Zhiyuan.Han  

[ChristopheG · Accepted solution]

Hi Zhiyuan.Han, thanks a lot for your answer.

As I now know that switch off the L4 doesn’t let anything in non volatil memory, I will investigate other parts of the software. I may have problems with storage of measurements before send them by radio.

Regards