There is a compromise between the value of the resistors used for boot programming, and the permanent load they put on the I/O system during operational I/O.
So, yes, you can lower the value of the programming resistors, if it both solves your boot problem, and does not disturb the way the I/O works when the system is in normal operation. At some point it will. The output drive capability of the GPIO on the Sitara is limited. Make sure you understand it. And make sure you are allowing for noise margin on both the boot logic signals and your operating logic signals. A battery powered motor and servo system can have a lot of electrical noise, both on the power and the ground system. If you have system noise getting into the boot and control logic, you end up with intermittent problems that are extremely hard to debug. --- Graham == On Monday, August 24, 2015 at 6:41:35 AM UTC-5, Frédéric wrote: > > Le 11/08/2015, Graham a écrit : > > > If you look at the diagrams in the System Reference Manual, the BBB uses > > 100K Ohm pull up and pull down resistors to tell the processor how to > > boot. So any load low enough to cause a line with 100K Ohm pull up or > > pull down to change logic state will cause boot problems. I would > > estimate that any load, less than 200 K Ohms can cause this problem, > > even though it is an "Input". > > I guess that only pull-up boot pins are concerned by a too low load? > > Do you think I could add another resistor in // with the 100k of the BBB, > to try to avoir it? > > -- > Frédéric > -- 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.
