dcgong2917 opened a new pull request, #19945:
URL: https://github.com/apache/nuttx/pull/19945
## Summary
Adds an on-chip RTC driver for the Realtek Ameba family, exposed as a
`/dev/rtc0` date/time character device with alarm support. The driver
lives in
the shared layer `arch/arm/src/common/ameba/ameba_rtc.c` and is wired into
three
ICs — rtl8721dx , rtl8720f and rtl8721f — reusing the common code
unchanged.
Design notes:
- Sits on the SDK fwlib RTC API (mirrored structures + local externs, no
vendor
headers pulled into the NuttX include world). The fwlib RTC API lives in
the
RAM source `ameba_rtc.c`, added to the fwlib build under
`CONFIG_AMEBA_RTC`
(both Make and CMake).
- Provides both the lower-half RTC (`ameba_rtc_lowerhalf`; alarm
set/cancel/relative + upper-half callback) and the arch date/time hooks
(`up_rtc_initialize`/`getdatetime`/`settime`, `g_rtc_enabled`), so NuttX
system time is seeded from the RTC.
- The hardware keeps a year plus a day-of-year (no month/day register); the
driver bridges that to the NuttX calendar with the libc UTC routines
(`timegm`/`gmtime_r`), which is exact and reversible. Cold start seeds
the
build date when the stored year predates `CONFIG_START_YEAR`.
- The only per-chip fact — the RTC interrupt vector — lives in the per-chip
`ameba_rtc_chip.h` (46 / 33 / 41); the shared driver is never edited for
a new
Ameba chip.
A `rtc` board profile (examples/alarm) is added to each board for
verification,
and the board documentation is updated.
## Impact
- New peripheral, opt-in via `CONFIG_AMEBA_RTC` (default n). No impact on
existing configs.
- Affects rtl8721dx / rtl8720f / rtl8721f only.
## Testing
- `tools/checkpatch.sh -g master..HEAD`: all checks pass.
- Builds and links cleanly on all three ICs (rtl8721dx, rtl8720f,
rtl8721f).
- Hardware: verified on all three EVBs (rtl8721dx, rtl8720f, rtl8721f)
with the `rtc` config, exercising every driver path:
- **Cold start / seeding**: on first power-up the RTC reads back the
seeded
build date instead of a pre-epoch value, so `date` is valid
immediately.
- **Read / set (`RTC_RD_TIME` / `RTC_SET_TIME` via NSH `date`)**: the
year/day-of-year hardware model is correctly bridged to the full
month/day calendar in both directions.
- **Timekeeping**: consecutive `date` reads show the clock advancing in
real
time.
- **Alarm (`RTC_SET_ALARM` + IRQ callback via `alarm` example)**: a
one-shot
alarm fires once at the requested offset and does not re-fire.
Representative NSH session (rtl8721dx):
nsh> date
Tue, Jun 16 00:00:07 2026 # seeded build date after cold start
nsh> date -s "Jun 16 12:00:00 2026"
nsh> date
Tue, Jun 16 12:00:06 2026 # set time read back (+ elapsed
seconds)
nsh> date
Tue, Jun 16 12:00:09 2026 # clock advancing
nsh> alarm 5
alarm_daemon: Running
Opening /dev/rtc0
Alarm 0 set in 5 seconds
alarm_daemon: alarm 0 received # fires once, 5 s later
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