I’ve made quite simple sketch (schematic attached):
MKR1000+MKR2UNO with one I2C bus split to 3.3v part and 5v part by 4channel bi-directional level converter from Sparkfun. On 3.3v side a FRAM chip and TMP102 (tested without 5V - worked fine).
On 5V side, just a single PCF8574T with one output charged with red LED and 470Ohm resistor.
GND,5V,3.3V - from MKR2UNO board. Ground continous througout the whole circuit.
No pull-ups used, as all breakouts, and level converter allready had pull up resisors.
With this circuit I was able to fry my MKR1000, after downloading and running my code, which just tried to set high to one of PCF8574 output and read temperatire and first 23 bytes from RAM.
Circuit did’t made any harm to MKR1000 until I downloaded the code. After running my code all communication is lost and Arduino is dead, no reaction to resetting, no USB recognized etc…only power Supply led is On.
My question is: what error did I make that I should avoid in my next attempt.