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.
