Hi Tim That comment in the source code is based on the fact that, with SPIDev you don't open the SPI port and then tell it later what CS line you wish to use. SPIDev associates both the port and the CS line with the device file and you open one of those for each CS device. For example /dev/spidev1.0 and /dev/spidev1.1 both send and receive through the SPI0 port but one activates the CS0 line and the other the CS1 line during transmission.
All the code comments are saying is that if you are using GPIOs as CS lines you can either open /dev/spidev1.0 or /dev/spidev1.1 (for example) so you can write to the port but you should not electrically connect anything to the pin where the corresponding CS line is located. Every transmission through the port will always toggle the devices associated CS line - there does not seem to be any way to tell it not to do that. If you have a device connected to that built in CS line it will get activated along with whatever device you are also activating with the GPIO. This would cause two slave devices to try to write to the SPI bus at the same time - not good. -- 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.
