@Harvey Ah, good one ! I was just thinking "inverter" when I saw your post, but I am not an electronics engineer by any stretch of the imagination . . . wasn't sure it would work.
@Winston. OK, my bad. I was actually thinking this could be the case, but was unsure. Harvey's suggestions seems plausible though. On Sat, Apr 11, 2015 at 10:36 AM, Harvey White <ma...@dragonworks.info> wrote: > On Sat, 11 Apr 2015 09:38:47 -0700 (PDT), you wrote: > > >On Thursday, April 9, 2015 at 11:48:35 PM UTC-4, William Hermans wrote: > > If the actual driver has an enable pin, then take an active low > (during initialization) pin, pull it down with a further resistor > (just in case), and then run that through an inverter (if needed) to > the enable on the MAX3222. > > That way, the default behavior is disabled (for the driver), and > during bootup, the behavior is still disabled until your code > specifically enables the driver. > > Harvey > > > > > >> *The 10K pull-up didn't work. I didn't think it would, the am335x > drives > >>> the pins low during initialization and this is overcoming the pull-up > [the > >>> outputs were never free-floating]. I think I should have used a > MAX3222 > >>> and wired up the SHDN pin to a GPIO so that I could independently > enable > >>> the level converter once the system is stable (assuming I can figure > out > >>> the .dts incantation to make a GPIO pin work under jessie/3.14-ti).* > >>> > >> > >> Winston is it ? > >> > > > >Yes. > > > > > >> Anyway, you could use Charles S' universal-IO device tree overlay(s) > >> to do this for you. I understand that they are built into the latest > >> images ( for several months now ). > >> > >> https://github.com/cdsteinkuehler/beaglebone-universal-io > >> > >> I meant to demonstrate this and write up a mini how-to, but have been > >> really busy for the last several months . . . > >> > > > >I think my issue is more fundamental. The issue is really that the RS232 > >peripheral is connected when the BBB boots, for those first few ms, before > >it's even loaded u-boot, the pinmux is at it's default "zero" state and > the > >UART pins are thus low which the peripheral reads as a stream of 0's, this > >continues until the dtb (I'm using jessie/3.14) is loaded that enables the > >UART via the pinmuxing. > > > >I had even tried building a custom version of u-boot that enabled UART5 > >(whereas normally it only enables UART0 for the console). Sadly, it still > >isn't quick enough for the peripheral not to see enough 0's to cause a > >serial break. > > > >Thanks! > > -- > 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 beagleboard+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
