On 9/6/14, 10:47 AM, "[email protected]" <[email protected]> wrote:
>Ben Gamari <[email protected]> wrote: >> [-- text/plain, encoding 7bit, charset: ISO-8859-15, 23 lines --] >> >> [email protected] writes: >> >> > In the BBB System Reference Manual the P8 and P9 pinouts are >> > documented with 7 modes for each pin which provide different uses for >> > the pins. >> > >> > All of the actual software and descriptions I can find about the BBB >> > hardware just talk about the Device Tree and Device Tree overlays. I >> > have already (sort) begun to understand the Device Tree system and I >> > have actually done a (trivial) recompile of the Device Tree to change >> > one of the I2C clock frequencies. >> > >> > Do the modes in the manual have any relevance at all now? I.e. can I >> > actually start the system in a specified mode? Or are they just >> > history, or what? >> > >> If you are writing a device tree you will need to refer to the pin modes >> to configure the pinmux. >> >OK, but I can't really find out *how* the PinMux/Modes are referred to >in the device tree. In fact it seems very difficult to find how the >entries in the Device Tree are mapped to the actual pins, I get the >feeling that it's actually rather simpler than it appears at first >sight but I'm still at the rather lost stage. > >The other trouble is that if you look for 'how to enable the UARTs on >BBB' there are many ways of doing it:- > > Edit the device tree in /boot/uboot/dtbs - this will (as I > understand it) remap things at boot time. > > Create a Device Tree Template for just the things to change, this > 'overlays' the Device Tree so is possible at run time (again, my > understanding) > > Edit the uEnv.txt file, I assume this controls the above but it's > far from clear. > >I'd love to find a document or tutorial that describes how this all >hangs together but there doesn't seem to be anything other than the >(huge) processor documentation which is vey much reference material >and (as I referred to above) various blogs etc. showing how to do one >particular thing but without any attempt to explain it. The pinmux section uses the register offset and in the attached spreadsheet, that offset is related to the P8/P9 connector pins. The right column defines how the pins are setup in the V3.15-bone5 device tree. Regards, John > >-- >Chris Green >ยท > >-- >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.
BBB Pinmux - 3.15.6-bone5.xlsx
Description: MS-Excel 2007 spreadsheet
