I’ve connected a VL53L5CS-SATEL ToF sensor to the MKR NB 1500 via the SDA and SCL lines, and everything works fine when powered and programmed via USB.
However, if I first unplug the USB and then power the board with a battery, the MKR NB 1500 fails to boot. After troubleshooting, I found that disconnecting the SDA line allows the board to boot, and I can reconnect it afterward without issues.
Obviously, manually disconnecting SDA at startup isn’t practical. Are there any workarounds to prevent the sensor from interfering with the boot process?
If sensor is completely disconnect, MKR booting fine. Then 3V3 and GND is wired from MKR to sensor, and SDA/SCL wired as well, 5V is not wired. It does not matter if EVK_PWR_EN is set to GND or +3V3 .
I know where to find Arduino schematics, the circuit that's interesting here and for us to help you better is your circuit, even if it sounds like a simple one.
From the arduino schematics, I find 4k7 to +3V3 for SDA/SCL (R13 and R14).
From ST schematics I find 2k2 for SDA/SCL (R4 and R5) to IO_VDD
In parallell that would become 1k5. Maybe that becomes to small?
According to the schematic you provided, the VL53 IC AVDD comes from the output of the 3.3V regulator but you need to cut a jumper and solder another if you don't use the regulator.
Howvere, you say it works correctly when connected via USB so the schematics must be different somehow.
Yes, slightly different schematics when connected to USB, then +5V from MKR wired to AVDD. And +3V3 to IOVDD. Maybe not right, but it works, MKR boots as it should.
Notice my schematic was updated after 2 minutes, wiring +3V3 with IOVDD.
Using only battery nominal 3.7V, AVDD is disconnected and MKR does not boot. Does not boot when AVDD is connected to +5V either, but I don't think AVDD should be wired for battery.
