ghnotgood opened a new pull request, #18853:
URL: https://github.com/apache/nuttx/pull/18853
Implementation of the Kinetis' Periodic Interrupt Timer (PIT). The lower
half driver is oneshot.
## Summary
Kinetis' PIT is not yet implemented. It is simpler than FlexTimer Module
(FTM) but good enough for oneshot timer-like use cases.
This PR implements Kinetis' PIT using oneshot count-based API.
Please, note that I am not completely sure about the `resolution` parameter
of the `oneshot_initialize` procedure. The frequency of the PIT depends on the
`BOARD_BUS_FREQ` and timing does not work as expected when something different
is used. I am probably missing something and I am happy to fix it when I
understand it. Thank you.
## Impact
Developers can
```
#if defined(CONFIG_ONESHOT)
# if defined(CONFIG_KINETIS_PIT_CH0)
struct oneshot_lowerhalf_s *oneshot0 = oneshot_initialize(0, 0);
if (NULL == oneshot0)
{
syslog(LOG_ERR, "ERROR: PIT0 initialization failed");
}
else
{
ret = oneshot_register("/dev/pit0", oneshot0);
if (OK != ret)
{
syslog(LOG_ERR, "ERROR: PIT0 register failed");
}
}
# endif
#endif
```
and then use `/dev/pit0` as oneshot timer.
## Testing
With the changes to .config
```
CONFIG_KINETIS_PIT=y
CONFIG_KINETIS_PIT_CH0=y
CONFIG_ONESHOT=y
CONFIG_ONESHOT_COUNT=y
CONFIG_EXAMPLES_ONESHOT=y
CONFIG_EXAMPLES_ONESHOT_DEVNAME="/dev/pit0"
```
I have run started our board:
```
__start: Reset status: 00:00
oneshot_register: devname=/dev/pit0 lower=0x1fff0564
NuttShell (NSH) NuttX-12.13.0
```
and run the `oneshot` example:
```
vtk15> oneshot
Oponeshot_ioctl: cmd=5664 arg=1fffa354
ening /deoneshot_ioctl: cmd=5665 arg=1fffa35c
v/pit0
Maximum delay is 71582788
Starting oneshot timer with delay 2000000 microseconds
Waiting...
Finished
vtk15>
```
The delay between `Waiting...` and `Finished` was approximately 2 seconds.
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