HI Graham, we like to just connect things we can order directly. Any extra chip, component we need to wire solder etc. should be prevented. Therefore we already pushed aside the i2c. I agree that this would be more stable but needs extra effort to build up many of them ;-) and no one sold us a full solution.
Therefore we like to use the baremetal BBB and as much as possible GPIOs directly. Speed ... no matters cos we switch on/off DSL modem power. hdmi, sound, .... not used.... pure console via J1 and ssh via wired Ethernet. I found a couple of examples for single or up to 8 GPIOs but no full setup. Immo On Thursday, April 20, 2017 at 3:24:40 PM UTC+2, Graham wrote: > Depending on how fast you need to control and respond to the GPIO, it may > be easier to > use the I2C bus and control some GPIO expanders. > > A chip like the PCA9555 will get you 16 each GPIO, and you can control 8 > of them on an I2C bus. > If you need more GPIO than that, you can buy other parts that occupy > different I2C addresses and > put another 8 times 16 GPIO on the bus. > > This also adds a layer of isolation between the BBB and the GPIO. The > GPIO pins on the > expanders are more rugged than the GPIO pins on the BBB, and a Voltage > spike would kill > the cheap expander IC, and generally, not the more expensive BBB. > > Depending on how you organize things, using the I2C bus approach will add > several milliseconds to > respond to, or command the GPIO. On the other hand, you are running under > Linux, which has it's > own delays and jitter that can be greater than that. > > So, how many do you need? and what are your timing requirements for > sensing the state of a pin > or commanding an output on the pin? > > --- Graham > > == > > On Wednesday, April 19, 2017 at 10:20:23 PM UTC-5, Immo wrote: >> >> Hi, I need the maximum possible GPIOs out of the BBB. >> I'll direct connect a optocopler to decouple the bbb form the external >> devices. >> But my first tries with P8 Pin 3-46 wher enot successful may be my >> overlay file is a bit to big. Or do somebody the same.? How about the boot >> pins ? If I use them as output do I have to pull them down anyway ? >> >> Immo >> > -- 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/a032b304-a196-4879-9b58-bdfa5bc5446c%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
