Additonal I2C port not outputing 5v if MKR1310 is powered from the VIN pin

Official Hardware MKR Family MKR WAN 1310
1

Hi All,

I have a project htat has a MKR GPS module that is connected to the Additional I2C port with the cable that was supplied with it.

If the MKR1310 is connected to a USB cable that is connected to a PC or 5v power source, the GPS Module powers up and works.

If the MKR1310 is not connected to USB and is powered by supplying 5v to the VIN pin, the MKR1310 powers up and runs, but can not talk to the GPS Module. When i check the pins on the I2C port on the GPS module, the 5v pin is only showing 1.4v

Do i need to do something else when powering the MKR1310 from the VIN pin. Am i also meant to provide VIN to the GPS Module too? I was hoping that the I2C cable would provide the power, because of project contrsaints, the GPS module is not right next to the MKR1310.

Did i miss something, or should powering the MKR1310 from VIN also provide power to the GPS Module.

Thanks

Ian...

2

Posting an annotated schematic would help us help you. Be sure to show all power, ground, power souorces and any other hardware involved.

3

Looking at the MKR1310 schematic, I don't think that will give a supply to the 5V pin. The MKR1310's DC-DC converter takes the voltage from VIN and produces a 3.8V output which feeds the 3.3V linear regulator. The 5V pin isn't fed any voltage in this configuration.

What I can't figure out is whether it's ok to power the board using the 5V pin, if you are supplying 5V externally. If so, that would also supply 5V to the i2c port.