YUN dont boot when...

i have a curious phenomenon with my YUN.
The sketch:
void setup() {

void loop() {

#ttyATH0::askfirst:/bin/ash --login

then YUN dont boot.

I try multiple times and today i found the reason.
Its a problem when send serial data during the boot.
I change the sketch
void setup() {

YUN is boot :slight_smile:

Yes, this is a well known issue. There are two different points where the Linux console allows interrupting booting by pressing any key, the idea is to enter a pre-boot mode where certain diagnostic/repair/upgrade commands can be issued. The Linux console port is the same one that is connected to Serial1 of the '32U4 processor. So, if the sketch on the '32U4 sends anything at those critical times in the boot process, it will interrupt the boot operation.

See How to improve reboot/reset stability for more information.