Hi Guy, is the source available for your SPI0 slave implementation on the BBB? I am running BBB Master <-> BBB Slave and am finding no examples for running the AM3359 in slave mode.
Thanks On Thursday, June 5, 2014 3:02:30 PM UTC-7, Guy Grotke wrote: > > Yes, I was talking about trying to do hard real-time data collection in a > user-space program. If you look at the maximum interrupt latencies from > other stuff running on the system, then you see just why PRUs are necessary > to always meet your deadlines. Most of the time, a user-space program > running mmap to access gpios will run up at Mhz speeds but every now and > then one of your data samples might be 100 msec late because something else > was running. That kind of irregular sampling makes an FFT worthless. (But > there certainly are some slower speed control applications where that kind > of latency is perfectly okay.) > > I have a program that runs the SPI0 port as a slave, and it can be clocked > by the master SPI device at 12-16 MHz because my protocol never overflows > the SPI FIFOs. I had to use mmap, so I could set SPI control registers in > ways no Linux drivers support. > > On 6/5/2014 11:53 AM, Brandon I wrote: > > > but you can't run the clock much faster than 1 KHz using a user-space > program under Linux. > > Not true at all! You can get over 3MHz just fine with mmap to the gpio > registers. If you try to open and close a file each gpio toggle, like the > insanely inefficient sysfs interface, then yeah...you'll be severely > limited, but still much faster than 1kHz. > > Did you google? > http://e2e.ti.com/support/arm/sitara_arm/f/791/t/296484.aspx > > On Thursday, June 5, 2014 8:31:24 AM UTC-7, William Hermans wrote: >> >> Sounds like fun. Good luck :) >> >> >> On Wed, Jun 4, 2014 at 2:17 PM, <swapn...@gmail.com> wrote: >> >>> Hey William... >>> >>> I do know that the Chip Select line can be used to toggle between >>> different SPI units... But I need data to be collected simultaneously from >>> multiple sensors... As of now I have 32 sensors - I have clubbed them into >>> groups of 4 and so I have 8 sets of SPI units that I want to communicate >>> with "simultaneously"... >>> >>> >>> On Wednesday, June 4, 2014 11:46:21 AM UTC-4, William Hermans wrote: >>> >>>> It sounds as though you need to read more concerning what SPI >>>> actually *is*. >>>> >>>> *Devices communicate in master/slave mode where the master device >>>>> initiates the data frame. Multiple slave devices are allowed with >>>>> individual slave select lines. Sometimes SPI is called a four-wire serial >>>>> bus, contrasting with three-, two-, and one-wire serial buses. SPI is >>>>> often >>>>> referred to as SSI (Synchronous Serial Interface).* >>>>> >>>> >>>> http://en.wikipedia.org/wiki/Serial_Peripheral_Interface_Bus >>>> >>>> What does this mean ? Multiple devices can share the same data bus, >>>> and only CS( chip select ) needs be different for each device. CS only >>>> needs to go high, or low, which hey remarkably is exactly what GPIO pins >>>> do >>>> ! :) >>>> >>>> >>>> On Wed, Jun 4, 2014 at 7:37 AM, <swapn...@gmail.com> wrote: >>>> >>>>> I am trying to run multiple SPI modules (more than the two available >>>>> on the BBB) to try and read data from a bunch of accelerometers >>>>> (LSM303D). >>>>> >>>>> I was therefore wondering if it would be possible to implement the >>>>> SPI module using code (preferably C/C++) on the abundant GPIO pins. I >>>>> have >>>>> been scanning through a lot of documentation but I cant seem to find >>>>> anything that fits the bill. >>>>> >>>>> Please help --- getting desperate... >>>>> >>>>> >>>>> -- >>>>> 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 beagleboard...@googlegroups.com. >>>>> >>>>> 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 beagleboard...@googlegroups.com. >>> 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 beagleboard...@googlegroups.com <javascript:>. > 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 beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
