Immo: Well, read the system Reference Manual Section 8 carefully.
The GPIO pins associated with "Expansion Boot Pins" can generally not be used without additional external circuitry. (mostly the same pins as the LCD Conflict Pins). If you are using the eMMC, then you can not use the eMMC conflict pins. Does everything else leave you with enough GPIO pins to do what you want to do? --- Graham ==== On Friday, April 21, 2017 at 1:53:05 AM UTC-5, Immo wrote: > > 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/fe534af2-e9b5-4294-9d82-ec3dc0f854af%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
