You need to put an oscilloscope on the 5 Volt output from the Pololu. There is a rise time specification on the start-up Voltage rise time. I think it needs to reach 5.0 Volts in less than 50 milliseconds. Read the System Reference Manual
The Voltage can not overshoot more than a few tenths of a Volt. The operating Voltage should be 5.0 Volts plus or minus 0.25 Volts. If it overshoots or undershoots above 5.5 or below 4.5 for even a millisecond, the PMIC will shut down. A properly designed 12 Volt to 5 Volt converter will work fine, every time. --- Graham == On Thursday, May 11, 2017 at 8:45:29 AM UTC-5, PM wrote: > > Hello, > > Thanks for your reponse. > > I meant that after the power is beeing supplied to the BBB. I have to hit > the POWER button in order to make it start. > > I did not have to do this when it was powered from sector. > > Le jeudi 11 mai 2017 15:27:50 UTC+2, cmbaker3 a écrit : >> >> You could add a toggle switch between the power supply and the BBB, or >> more simply just not power the BBB down. Leave it up. >> Chad >> >> On 5/11/2017 7:54 AM, PM wrote: >> >> Hello, >> >> I am trying to power my BBB from an external 12V source. >> >> I convert it to 5V using D15V35F5S3 step down convertor from Pololu. >> >> When I connect it to SYS_5V it works but I have to always hit the power >> button before the lights go on. >> >> Do you know any way to not to have to hit the POWER button ? >> >> Thank you very much. >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/beagleboard/8ed61f6b-415c-4418-832f-f696b9560441%40googlegroups.com >> >> <https://groups.google.com/d/msgid/beagleboard/8ed61f6b-415c-4418-832f-f696b9560441%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> For more options, visit https://groups.google.com/d/optout. >> >> >> -- >> Chad Baker Memphis, TN >> > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/a8b6246b-413f-46db-86e9-f7edf871465f%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
