Hi,
Sometimes, by Arduino starts to blink CHRG led very fast when I plug it into USB and I don't get any message on serial.
It is ok after I plug and unplug it few times, but I do not understand why it does that.
Thanks
The the charge / battery light blinking is normally nothing to be concerned about.
It has the same behaviour on some other MKR boards where it will flash after a period or sometimes when freshly connected.
When in use with a LiPo its behaviour changes to indicate charge status etc.
When the charge LED blinks rapidly, the board is most likely in boot loader mode.
It will switch the running the sketch shortly. You can also look at the USB id of the serial port to see what mode it's in.
It looks like in the last few days is was ok.
I have another question, can I connect a power source on the battery connector and having an USB in the same time? I want to be able to change the voltage and to send it on serial on the same time.
Not heard of anyone using anything other than a LiPo on the battery connector.
However you could use the VIN and GND pins to supply the board but do not exceed 5 volts.
Thats what they are there for./
It looks like the CHRG led is blinking very fast and my board is not recognized by the laptop when I have something connected to I2C. I have not an accelerometer sensor and if I disconnect it everything is ok. I used it yesterday without problems, but today something does not look ok for it...
I found the problem. I was connecting by mistake the interrupt pin from the accel to SDA. The charging IC from the boards is connected to I2C as well
Makes sense, the SAMD boot loader and core try to configure the PMIC via I2C on boot. If something is interfering on the I2C pins this will fail as you observed.