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nRFX v2.0.0 NRFX_SWI_USED -> NRFX_EGUS_USED?

Andrew Fernandes

Hello, and thank you for making the nRFX components open-source on GitHub!

Now I realize that it's only been up for a day :smile: but most of the changes are reasonably self-explanitory.

The only thing I am asking for confirmation on is the dropping of the SWI driver and it's replacement with the EGU driver.

Is it correct to suppose that NRFX_SWI_USED has been effectively "renamed" to NRFX_EGUS_USED (with value 0x3C for SoftDevices 7.0.1)?

For NRFX_PPI_CHANNELS_USED, NRFX_PPI_GROUPS_USED, and NRFX_TIMERS_USED I can look at the "SoftDevice Specification" and rationalize those values with the ones found in "nrf_sd_def.h".

But the derivation (and correct value) of NRFX_EGUS_USED escapes me.

Thank you!
-Andrew.

  • 0

    So I spent a little more time with the documentation, and I'm even more confused.

    Take, for example, the "S132 SoftDevice Specification v7.1", Tables 4 and 5.

    They seem to imply that EGU4/SWI4 and EGU5/SWI5 are hard-reserved for the SoftDevice, but EGU/SWI3 is open. But bit three in NRFX_SWI_USED (for nRFX v1.8.1) says that SWI3 is used by the SoftDevice.

    My reading of the Specification says that NRFX_EGUS_USED (for nRFX v2.0.0) should be:

    • EGUs 1, 4, and 5 noted as used (0x32), and
    • only 4 and 5 (0x30) are used if softdevice radio notifications are not used.

    I think what's confusing me is where the old (v1.8.1) value of NRFX_SWI_USED = 0x3c = 0b111100 came from...

    That and the fact that (I think) only EGU1 and EGU5 are used by the softdevice, so if you are comfortable sharing the SWI1 and SWI2 interrupts with the EGU1 and EGU2 interrupts...

  • 0 in reply to Andrew Fernandes

    Okay... looking through the source of nrfx_egu.c it's pretty clear that the new EGU driver cannot share interrupts.

    So, it looks like NRFX_EGUS_USED should be set to 0x36 (only EGU0 and EGU3 available) for the softdevice on the nRF52832 and nRF52840, correct?

  • 0

    Hi,

    Is it correct to suppose that NRFX_SWI_USED has been effectively "renamed" to NRFX_EGUS_USED (with value 0x3C for SoftDevices 7.0.1)?

     Yes. The EGU "uses" the software interrupts, and the EGU and SWI Peripheral shares the same Base Address, so they cannot be used independently at the same time. Take a look at the memory map at this link.

    Looking at the SDS, chapter "Application signals – software interrupts", see this link, the SoftDevices uses SWI/EGU 2,4 and 5. The application could use SWI/EGU 0,1(if SD is not configured to use Radio Notification) and 3. So the correct value for SD_SWI_USED would be 0x34(0b110100). The value 0x3C is wrong, and is from SoftDevice v.3 and earlier, when also SWI/EGU 3 was reserved by the SoftDevice.

  • 0 in reply to Sigurd

    Okay - that's the same conclusion that I came to!

    Incidentally, the 0x3C value is from the nrf_sd_def.h file in the most recent nRF5_SDK_16.0.0_98a08e2 SDK with SoftDevices 7.0.1 - so that should probably be fixed... :smile:

    Thank you!

  • 0 in reply to Andrew Fernandes
    Andrew Fernandes said:
    so that should probably be fixed

    Yes, thank you for reporting this. I have reported it to the team responsible for this file.

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