The Sitara uses a field of pull-up and pull-down resistors to tell it how to boot. If you put any LOAD on these pins, and your I/O does NOT have to be powered, (which would make things even worse), you will give it the wrong boot commands, and the BBB won't boot.
Go read the section in the System Reference Manual on Boot Configuration, and the section on Pin Usage Considerations. --- Graham == On Tuesday, March 24, 2015 at 9:42:12 AM UTC-5, Khalil Estell wrote: > > Hello All, > > I have become stumped by this issue. I am trying to boot up a BBB when > connected to the inputs of six MD10C motor controllers > <http://www.robotshop.com/media/files/pdf/user-manual-md10c-v2.pdf>. For > the most part, it works fine if the BBB has been boot up before > *connecting* the direction and pwm pins to the beagle bone black. If I > attempt to power the BBB with them connected, the power light indicator > will come on, but the status lights will not. The configuration of the > circuit is this: I have a custom shield that I made that breaks out the pwm > pins and gpio pins I need for the controller. The controllers are powered > by an 24V battery power supply rated at 15A output. The BBB is powered by > 5V regulator rated at 6A. > > Here is what I have attempted thus far: > > > 1. Turn on battery, which is powers the 5V regulator and the motor > controllers, which turns everything on at the "same" time. BBB does not > boot up. > 2. Remove cape (with all the connections still on), turn on battery, > BBB boots, once the light indicators are no longer all a solid blue, I > replace the cape, and everything works, BBB continues to boot up. > 3. If I remove all but one input to one controller and power up the > battery, BBB sometimes boots. > 4. I have attempted to add 1k and 10k resistors between the > connections which allowed the BBB sometimes to boot with two motors inputs > connected. > 5. *Wierd one:* I decided to remove the power from two controller > (except for ground), and connect them to the BBB. Still it did not boot. > The motor controllers did not get powered at all! > 6. *Wierder one: I removed all of the power wires from from both > controllers and still the BBB will not boot up if connected to the motor > controller inputs.* > > Does anyone have idea what is happening here? One of my solutions was to > use a relay to turn on the power to the motor controllers after the BBB has > fully booted up or add a second switch that turns on the motor controllers > after the BBB has fully booted, but that plan can not work if merely > pluggin in the inputs causes this problem. > > I do know about this issue: DO NOT APPLY VOLTAGE TO ANY I/O PIN WHEN POWER > IS NOT SUPPLIED TO THE BOARD. IT WILL DAMAGE THE PROCESSOR AND VOID THE > WARRANTY. NO PINS ARE TO BE DRIVEN UNTIL AFTER THE SYS_RESET LINE GOES > HIGH. But in this case, there is no power coming from the input pins. > > *Last note: I measured the resistance from the dir pin and the pwm pin to > ground and they come up 16k and 20k respectively. * > > I appreciate any suggestions or help on this matter. > -- 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.
