On Fri, 11 Mar 2016 09:29:07 -0600, you wrote: >I would not recommend shorting outputs of two processor together, something >might get fried.
Exactly right, the output drivers will likely overheat and perhaps be damaged when one chip is outputting a different state than the other. In this case, it was a single output driving two inputs. With properly connected grounds, there shouldn't be a problem with multiply connected outputs. However, the question may be one of voltages. The maximum voltage input to the processor is 3.3 volts, and if driven by a 5.0 volt source can certainly damage the processor. Paranoid design would have a buffer (running from the processor's VCC) connected to the real world, input to the real world, output to the processor. At the other end (driving end) you use another buffer to drive the line, both must be either inverting or non-inverting. For each additional input to another processor, use another buffer. If the processors use different supply voltages, then you would want a circuit to translate the voltage levels. There are chips that are designed to do that. I use a similar idea when connecting I2C driven systems (PCA9517 works well). RS-232 drivers work the same way, and in fact, would be very tolerant of voltage level differences. I'd suggest a MAX232 style chip. The outputs of the chip are +/- 9 volts, so absolutely cannot be connected directly to a processor. Harvey > >Gerald > >On Fri, Mar 11, 2016 at 9:27 AM, Jordi Segura <jord...@gmail.com> wrote: > >> Related to my unanswered problem below, main point I want to know is: >> >> Is it safe to connect directly the same Tx external signal simultaneously >> to a couple of BBs ? >> >> Cheers, >> Jordi >> >> El dilluns, 7 març de 2016 0:11:32 UTC+1, Jordi Segura va escriure: >>> >>> My BBGreen got fried (when I power it up it just dims once the power led >>> and that's all it does). >>> >>> >>> Can someone explain me what I did wrong so it won't happen to me or >>> others again? >>> >>> >>> Explanation of what I did: The BBG died after several days working 24/7, >>> powered up from a power supply 5V 2A, with an 3G usb dongle connected on >>> it, and (maybe that's my fault ...) I connected the Tx output of another >>> microcontroller to one Rx input of the BBG but also to one Rx input of a >>> BBB (I had both the BBG and the BBB receiving the same Tx signal from a >>> third micro) >>> The same power supply was powering both systems (BBG and BBB) and I also >>> interconnected GNDs. The third micro sending the Tx signal was powered from >>> the BBB. BBB is working well so far. >>> >>> >>> Cheers. >>> >> -- >> 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. >> > > > >-- >Gerald > >ger...@beagleboard.org >http://beagleboard.org/ -- 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.
