Hi Guys,
We are sorry for late response.
Yes, the Chip is PCB9306 level Shifter.
Effect is:
I2C communication, short the power.
Result is:
I2C not work(cannot read the RTC…);
Dim power LED;
Cannot upload sketch…
This Problem appeared in our test, but just a few of them(5/300);
But now, it seems a big and serious problem.
We have check the schematic and PCA9306 datasheet, and found out the problem maybe the UartSB voltage which is direct come from USB port.
If the USB port Voltage is more than 5V, it will burn this chip, and it will not come back to work anymore.
Here has a solution to avoid the USB power, power the Stalker V1 from EXT JST power Jack, and toggle the UartSB power switch to 3.3V side.
As the EXT power has a Diode in Series, the supply just 4.6~4.8V, it is safe for PCB9306.
For the burned customer,
Please contact our Product Engineer kevin.hai{at}seeedstudio.com for a replacement.
Much sorry for the bothering.
Albert