UART_RX has *active* level "0", i.e. pulled down. In order to have an idle state you should pull RX up to 3.3V.
2014/1/24 nitesh singh <[email protected]> > Thanks a lot Dennis . That was quite an insight. > Actually we have placed that 100k resistor. Nowdays, the board is showing > less of those kernel crashes. > On Jan 23, 2014 11:50 PM, "Dennis Ferguson" <[email protected]> > wrote: > >> Hello, >> >> If you are still having the problem try to boot the kernel without the >> console connected but with a jumper connecting UART0_RX to DGND on the >> console port (that's pins 1 and 4 on the 6-pin console connector, if you >> have one). >> >> If you leave the console uart receive pin (or any of the other uarts, I >> think) unconnected and unterminated it will pick up noise, and the stream >> of noise will find bugs in the kernel terminal driver and cause crashes. >> Revision A5A of the BBB board got a 100k pull-down resistor attached to the >> UART0_RX pin to prevent the noise (I assume), if your board hasn't got a >> similar pull-down or pull-up you can have the difficulty you see. In fact, >> even if your clone board includes the 100k resistor like a real BBB you may >> have problems with this. I have two revision A5C BBB boards which also >> cause kernel crashes in the serial driver when no console cable is >> attached, though I have a handful of other boards which run reliably that >> way, so I think the 100k value is marginal at fixing this on a real BBB. >> Decreasing the resistance fixes these. Even if your clone board includes >> the 100k pull-down the differences in board layout or construction may make >> the 100k value less effective than on a real BBB (where it seems to just >> barely work) so you may need to use a smaller value. >> >> Dennis Ferguson >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to a topic in the >> Google Groups "BeagleBoard" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/beagleboard/1rbO7JGhppw/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> >> For more options, visit https://groups.google.com/groups/opt_out. >> > -- > 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]. > For more options, visit https://groups.google.com/groups/opt_out. > -- LinkedIn - http://www.linkedin.com/in/maximpodbereznyy Company - http://www.linkedin.com/company/mentorel Facebook - https://www.facebook.com/mentorel.company -- 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]. For more options, visit https://groups.google.com/groups/opt_out.
