Thank you everyone! I appreciate the responses. After days of trial and error I managed to setup the IVT and configure one of the timers to fire an interrupt on overflow. For me, I found this resource pretty helpful: https://android.googlesource.com/kernel/lk/+/upstream-master/platform/am335x - it appears to be the embedded android kernel ported to the beaglebone. They have some good interrupt stuff in there, as well as device-specific peripheral drivers.
I'm struggling now with "de-triggering" an interrupt after it fired. So my timer fires one interrupt and then the IRQSTATUS_RAW keeps its value, no matter how many ways I try to reset it. So I am only handling it once. I feel I'm close though. Hopefully the resources shared + the anrdoid kernel I found will shed some light on how to correctly process an interrupt. Cheers! On Monday, March 8, 2021 at 8:23:10 AM UTC-8 lazarman wrote: > Yes I agree. Make sure to look at startup assembler language file many > times vectors are in it. Start or start-up. Asm > > Sent from Yahoo Mail on Android > <https://overview.mail.yahoo.com/mobile/?.src=Android> > > On Mon, Mar 8, 2021 at 9:56 AM, Graham Stott > <gbcs...@comcast.net> wrote: > > You could look at the TI starterware code for examples of setting up the > interrupt table and the code at the tables. > > > > Graham > > > > *From:* 'Mark Lazarewicz' via BeagleBoard [mailto: > beagl...@googlegroups.com] > *Sent:* Sunday, March 07, 2021 12:30 PM > *To:* beagl...@googlegroups.com > *Subject:* Re: [beagleboard] Re: BBB Setting up the Interrupt Vector Table > > > > Your handler needs the keyword interrupt to save the registers so when the > vector occurs whatever was running isn't corrupted > > > > Besides interrupt vector table don't forget exceptions they need a vector > as well as in bus error or address error > > > > Here's a brief reference you should look for interrupt code to verify and > the correct arm programming guide > > > > > > > https://community.arm.com/developer/tools-software/tools/f/armds-forum/13621/need-interrupt-handling-code-for-arm-cortex-a9 > > > > > > Sent from Yahoo Mail on Android > <https://go.onelink.me/107872968?pid=InProduct&c=Global_Internal_YGrowth_AndroidEmailSig__AndroidUsers&af_wl=ym&af_sub1=Internal&af_sub2=Global_YGrowth&af_sub3=EmailSignature> > > > > On Sun, Mar 7, 2021 at 12:01 PM, Josh Cole > > <three...@gmail.com> wrote: > > Update! > > > > I've solved my own problem and thought I'd share for any lost soul in the > future who seeks these answers. > > > > If you look at the technical reference manual for the am355x section 26-3 > it shows an interrupt vector table which exists wildly far away from your > application entrypoint. Upon closer inspection, I realized some entries are > listed twice. This is because the interrupt vector table is actually a > bunch of indirection. > > > > If you want to set the IRQ branch *address* you specify the address at > location 0x4030_CE38 > > If you want to set the pre-fetch abort *address* you specify the address > at location 0x4030_CE2C > > > > Example code: > > // Set the IRQ handler to the entrypoint of the application + 24 bytes > > *(0x4030_CE38 as *mut u32) = 0x402F_0400 + 0x18; > > > > I assumed I needed to write an actual branch *instruction* to those > locations. Which is where my confusion started. So if you are building a > low-level kernel and are working with interrupts, just remember that the > vector table can be updated by simply writing the correct *address* to > your handler based on the vector table in the reference manual (*not *an > actual branch instruction). > > > > On Friday, March 5, 2021 at 6:12:00 AM UTC-8 Josh Cole wrote: > > Hi everyone, > > > > I'm working on a low-level kernel for the Beaglebone Black. I've gotten to > a point in my project where I want to specify an IRQ handler and enable > interrupts. > > > > According to the technical reference manual > <http://www.sal.wisc.edu/st5000/datasheets/tq-systems/spruh73p.pdf>(section > 26.1.4), there are two primary locations you can load a disk image to. The > first is what they call "Public ROM" which seems pretty straightforward. > You load your image to address 0x20000 and the interrupt vector table is > the first thing which gets encountered. > > > > The second location you can load an image is "Public RAM" (which I'm > using). This starts executing at 0x402F0400 and you get 109kb of space for > your application. The weird part is, *the interrupt vector table > appears to be located super far away from the entrypoint*, at location > 0x4030CE00. This is more than 109kb away, so it can't be included in the > image which gets flashed to the device. > > > > I am at a loss about how to get an instruction to that particular location > in memory since my image fundamentally can't be that size. Any guidance on > how to setup the IVT for Public RAM would be greatly appreciated. > > > > Thank you for your time! > > -- > 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. > To view this discussion on the web visit > > > https://groups.google.com/d/msgid/beagleboard/b63bc711-fcda-497b-b4e5-ee35c0081176n%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/b63bc711-fcda-497b-b4e5-ee35c0081176n%40googlegroups.com?utm_medium=email&utm_source=footer> > > . > > -- > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/1482309015.269358.1615148982352%40mail.yahoo.com > > <https://groups.google.com/d/msgid/beagleboard/1482309015.269358.1615148982352%40mail.yahoo.com?utm_medium=email&utm_source=footer> > . > > -- > 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. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/001001d71433%248d59d000%24a80d7000%24%40comcast.net > > <https://groups.google.com/d/msgid/beagleboard/001001d71433%248d59d000%24a80d7000%24%40comcast.net?utm_medium=email&utm_source=footer> > . > > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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