first off, to properly answer your question we need to start by referencing the datasheet for the part you wish to use found here: http://www.ti.com/lit/ds/symlink/sn74s02.pdf
something missed by many is that 3.3v OUTPUTS on a device such as the beagle will drive standard 5v TTL logic just fine! just make sure to limit your fan out (number of logic loads) appropriately. The reason for this becomes clear if one actually reads the datasheet referenced above for the part you wish to use. If you look at the 74LS02 VIHmin (the minimum voltage which the input sees as high) it's listed as 2v. since 3v3 > 2v0 it works fine. the problem you have is that the output of the 74LS02 swings from 0-5v so when the output of the 74LS02 goes high it will measure 5v. since 5v > 3v3 it will cook a 3v3 INPUT. So depending what you want to do you may or may not need voltage translation andin most cases (i2c buses being the major place where you find an exception and do need bidirectional) they need only be unidirectional and one may use simpler circuitry such as a transistor or resistance ladder/voltage divider. So I'll end by posing a question. What doyou want to accomplish with this and can you post a basic schematic for review for us tolookat and constructively comment on? Eric On Tue, Mar 10, 2015 at 10:50 AM, <[email protected]> wrote: > Hi, > > I come from the world of sotware engineering and I am a newcomer (nearly) > to the world of electronic. I would like to know if it was possible to > interface a 74LS02 to the BeagleBone Black. > > I plan to connect Vcc and Vss of the 74LS02 to the 5V Vdd output and Gnd > of the Beagle and use the GPIO pins to command the logic inputs. My problem > is that I don't know if I can plug the 74LS02 without components such as > resistors, in order to limit the current flowing through components. I > don't want to damage the board. > > The result of all the logic operations should be gathered by some GPIO > pins configured as inputs. > > Is it possible to proceed that way ? > > Thanks in advance for your answers > > -- > 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 [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
