nRFX PWM task register address mismatch between nrfx_pwm_simple_playback and nrfx_pwm_task_address_get

[lepton-7]

I've got an NCS v2.6.1 project on the nRF52832 running a timing chain using PPI for PWM instance 2:

#define STIM_PWM 2
nrfx_pwm_t pwm_instance = NRFX_PWM_INSTANCE(STIM_PWM);

...

uint32_t task_addr = nrfx_pwm_simple_playback(&pwm_instance, &biphasic_seq, 1, NRFX_PWM_FLAG_START_VIA_TASK);
uint32_t exp_addr = nrfx_pwm_task_address_get(&pwm_instance, NRF_PWM_TASK_SEQSTART0);
if (task_addr != exp_addr)
{
    LOG_ERR("Start trigger address unexpected (0x%x != 0x%x)", task_addr, exp_addr);
    fault_config();
}

The output of nrfx_pwm_task_address_get is 0x40022008 as I'd expect from the PWM peripheral registers table for PWM2

However, nrfx_pwm_simple_playback returns 0x40018008, which doesn't seem to match up to any of the addresses in the PWM table. Instead, I found that it seems to be in the address space of the SWI peripheral.

I'm currently using the return from nrfx_pwm_task_address_get in my PPI configuration. Is there a reason to use one or the other with nrfx_gppi_channel_endpoints_setup?

[Hung Bui]

Hi Lepton, 

Have you tried to reproduce the issue on a simple example ? 
I did a quick test here on a nRF52840 DK and it seems to work fine: 

nrfx_pwm_simple_playback return 0x4002200c

Could you try to test with the attached project (I haven't tested with nRF52832)
common_mode_pwm.zip

[lepton-7]

Hi Hung,

I couldn't quite get your project to build, but I modified the sample directly and added the log statement for the address.

Here's what I get for the nRF52832 devkit:

And here's the output from a nRF5340 devkit:

Looks like the base address is correct for the 5340 (0x50023000) but I don't recognise the offset from the table. This is all on NCS v2.6.1

Here's the return address on the 52832 DK using NCS 2.7.0:

And using NCS 3.0.2:

I unfortunately do not have a 52840 DK to compare results with you.