sabotaged arduino not transmitting!!

horror! some idiot connected the power supply to an external sensor that i had hooked up to arduino over a SPI, without powering up arduino first... and left it for hours. the sensor had it's own voltage regulated (LM7805) battery supply independent of arduino's supply.

i arrived to find arduino's power light and tx/rx lights flickering spasmodically...

so i disconnected everything, plugged in USB, hit reset, and uploaded "serial_read_advanced" from the examples to test things. the tx/rx lights flashed in a very normal looking way while it was uploading, and i got the standard "AVR ATmega8 found, firmware version 1.18" message.

when i open the serial monitor and send data to arduino, the rx light confirms it's receiving something, but nothing else happens - no transmitting. when i type 'H', the led doesn't light up. i added a line to Serial.print("hello") whenever data is recieved, but... nothing!! not even a flashing tx light.

the only thing that happens is that the pin13 LED flashes every 10 seconds (a kind of flickery looking flash, too...), but this seems to stop after two minutes or so.


anyone have any idea what the problem might be?? please tell me that the power from the sensor hasn't fried some critical part of arduino... this is how i had the sensor connected to arduino - the battery on the right is the one that got connected, while arduino had no power:

well, hope someone can help!!!



that should not have hurt it... the problem is they don't publish specifications for the ATmega chips when they're powered down!
Very unlikely though. Worst it could have done was burned the pins 2,3,4,5 if they were in a low state.


hmmmm... well, assuming nothing vital is burned out, is there any explanation for the LED flashing every 10secs?

could the ATmega8 have perhaps been somehow reconfigured by having arduino's pins 2 and 5 set to +5v without being switched on... and if so is there a way to restore settings?

the test is to swap that chip for a known good one...


yep i posted above..."i think i fried it" and i am getting similar results...ill get another chip and replace it, see what happens, and post results