SATEL-VL53L8 level conversion

milukic · ‎2023-12-11

Hi everybody,

I have purchased SATEL-VL53L8 package containing 2 breakout boards with VL53L8 ToF ranging sensor, and I encountered a peculiar hardware issue. A breakout board has been connected to an ESP32 dev board (3.3V logic level). I have been trying to get it working using SPI bus + ULD driver. When I call the vl53l8cx_is_alive function, a sequence of 4 SPI transactions is executed in order to confirm the presence of the chip on the SPI bus. I connected the logic analyzer to observe the SPI, and on the first glance everything looks fine:

However, the MCU always reads 0s on the MISO line. I have measured voltages on the PCB, and it turns out that there is a problem with logic level conversion. The logical 1 level is 1.8V both on the chip and on the MCU side, whereas it should be 3.3V on the EXT_MISO line.

As the package contains two breakout boards, I tried the other one as well to eliminate the possibility of having a faulty unit. It turned out that it behaves exactly the same, indicating that there is some kind of a systematic failure with logic level conversion on that line.

Any ideas what might be wrong?

Anne BIGOT · ‎2023-12-12

Hello,
as per the notification in the AN5945 if you use the break out board only, you need to power it with an 1.8V power supply.
Only the SATEL board can be used with a 3.3V power supply.

Hope this answer to your question,
Regards
Anne

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milukic · ‎2023-12-12

Hello Anne,

I probably didn't express myself correctly. I am using the SATEL-VL53L8 PCB as a whole, and I connected the EXT_5V0 pin to 5V, so the on-board regulators are providing correct voltage values (3.3V, 1,8V and 1.2V).

Anne BIGOT · ‎2023-12-13

Hello,

Indeed you should have 3.3V on EXT signals.

Did you put 5.0V on pin7, EXT_PWR_EN ?

How is the J3 jumper on your side ?

Regards

Anne

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milukic · ‎2023-12-13

Dear Anne,

For the testing, I have paused in the middle of an SPI transaction, so that I can measure voltage values:

This is the diagram showing the connections in green. In blue, you can see the measured voltages which are as expected, and in red we have the values which don't make sense.

In addition, the jumper is in the 1.8V position. Measurements on SPI_I2C_N and LPn pads show 2.2V, which also differs from the expected values (1.8V).

Please let me know if you need further details.

Kind regards

Anne BIGOT · ‎2023-12-15

Hello,

The EXT_PWR_EN needs to be fed with the same voltage as the VIN pin as per the datasheet of the LDK130M12R LDO.

This means the EXT_PWR_EN should be 5V and not 3.3V.

Best regards

Anne

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milukic · ‎2023-12-16

Hello Anne,

EXT_PWR_EN is now connected to 5V, but everything else remains the same.

Kind regards