Mistakenly powering the HAT when not on the Pi

[StefC]

Hi there,

I just received my HAT today and was pretty excited. I plugged it over my Pi4, plugged the Pi USB power, and everything seemed perfect (like, 3 LEDs turned on on the HAT, Pi booting).

Then I realised the 12V was not connected (I bought the power supply addon board) but could not figure out which pin was + and which was ground (as they are labeler under the board).
I took out the HAT, plugged the 12V as indicated BUT... I realised my 12V supply was already ON; so I happened to apply 12V power to the HAT while it was NOT on the Pi. 

Since then... nothing: turned off the supply, plugged the HAT on the Pi, but to no avail: the HAT no longer shows LED after power is applied..
Is it possible that plugging 12V while the HAT is not on the Pi made it blow up??! (Please, say that it is not the case...)

StefC

[Adrian]

The HAT should be fine with being powered from 12V while not mounted on the Pi.

Make sure that you also connect 12V SW as per documentation. Without that, there won't be any activity on the HAT as the power module will stay powered down.
https://macarthur-hat-documentation.read...power.html

[StefC]

The HAT should be fine with being powered from 12V while not mounted on the Pi.

Make sure that you also connect 12V SW as per documentation. Without that, there won't be any activity on the HAT as the power module will stay powered down.
https://macarthur-hat-documentation.read...power.html

Thank you Adrian for taking time to reply on that.
That'a reassuring but...

What maybe wasn't clear in my description is that, even after removing the power module and powering through USB, I still get no reaction from the HAT (none of the LED is ON).

That being said, if I remove the USB power, plug the power module, then connect GND, 12V power and the 12 V switch, I do get 2 LEDs: 12V and 5V. But nothing else. And the Pi is powered.

Should I not see more than those 2 red LEDs. If I remember correctly, when I initially powered by USB, I had more LEDs turned on (like 3 amber ones).

StefC

[Adrian]

The 5V on the MacArthur HAT only indicate that the power module is running. Confusingly, it won't light up when the HAT is powered from the Pi.

The other LEDs typically stay dark, until there is actual activity on those inputs/outputs. Only the CAN LEDs may light up without data traffic, depending on configuration and connections:
https://macarthur-hat-documentation.read....html#leds

[StefC]

Hi Adrian,

Well then, after all that, based on your tips I think everything is fine.
I swear that on the first power on (when powered solely by USB), at least 3 LEDs were lit: NMEA0183 Rx 1&2 and Seatalk.
Subsequent boots did not show any LED, which led me to think something was wrong. Might have been just some improperly initialized I/O pins or a random glitch.

BTW, I obtained the schematics for the board and that greatly helps me understand how it works.

Thank you Adrian for your quick support and your great work on that product.

StefC