On Mon, 27 Jul 2015 00:18:48 -0700 (PDT), you wrote: > >Alright, I know that there are a lot of discussions on here about this >topic, and I have read through them, but I am still a bit confused about >this line in the manual: >NOTE: 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. > >I am working on a project that will involve me using multiple sensors with >the BBB that are powered from another source. One of those sensors is a GPS >that spits out data as long as it is powered, but the others only send data >after they have received a request. Here are my questions:
Opinions follow: > >1. Based on that statement, it is my understanding that if the GPS I'm >using is powered and the BBB is not, then the BBB will be damaged. Is this >accurate? That's what it says. >2. What if the board and all the sensors are powered from the same source >controlled by a single switch? Will this damage the board when I flip on >the switch? The problem could be if the sensor power comes up before the board is fully powered up, and that would be a problem. >3. What if I power all the sensors from the board itself so that it is >impossible for them to receive power before the board does? Will this >damage the board? Better solution, and is only based on the board's capability of supplying the power. This is how the capes operate, IIRC. Another possibility is to have external power for the sensors controlled by either a relay or a solid state switch, biased so that the switch is off unless a voltage is applied to the switch control pin. This allows the sensors to be shut down for lower consumption if needed (or if useful), but does give you rather complete power control over the sensors. I'd use a bidirectional driver with separate power lines (normally used to do level translation). IIRC those chips do not drive with power off on one side. This not only protects the processor, but gives you some additional buffering. Harvey -- 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.
