Can the VENTUNO Q wake from full shutdown using the RTC `wakealarm`?

Official Hardware VENTUNO Q
1

Hi everyone,

I’m trying to shut down my Arduino VENTUNO Q and have it power back on automatically after two minutes, but it shuts down and does not wake.

I set the RTC alarm with:

echo 0 > /sys/class/rtc/rtc0/wakealarm
echo +120 > /sys/class/rtc/rtc0/wakealarm

The alarm appears to be programmed. For example, shortly after setting it, I saw:

/sys/class/rtc/rtc0/wakealarm: 451

rtc_time        : 00:05:31
rtc_date        : 1970-01-01
alrm_time       : 00:07:31
alrm_date       : 1970-01-01
alarm_IRQ       : yes
alrm_pending    : no

I understand that wakealarm reads back as an absolute RTC value: 451 seconds is 00:07:31, which is 120 seconds after the RTC time of 00:05:31. The system clock shows the actual date, but the RTC reports 1970-01-01.

I then shut down with:

shutdown -P now

The board powers off but does not start again when the alarm should fire.

Does the VENTUNO Q support powering back on from a full shutdown using the RTC alarm? If not, is there a supported suspend or low-power mode that can wake from this alarm? Are there any additional firmware, configuration, or hardware steps required?

Thanks!

2

As far as Arduino's own docs go, no. The VENTUNO Q datasheet only describes two ways the board comes back on: it boots by itself whenever power is applied, and after a long-press shutdown it "will remain off until power is disconnected and reconnected". Nothing about the RTC alarm powering it up, so what you're seeing after shutdown -P is what I'd expect.

The documented way to get a timed restart without pulling the cable is JCTL pin 10 (POWER_SWITCH_DISABLE_N). Pulling it below 0.85 V gates the main power switch, and letting go brings power back, so the board boots. So: shutdown -P now, then have something external on the same supply (small MCU, timer, whatever) pull pin 10 low through an open-drain output for a second, two minutes later. Read the JCTL warning box first. Pin 10 has no TVS, it's tied to VIN through an internal divider, and it must never see more than 5 V, so open-drain only, never drive it high. The datasheet describes it as the VIN switch, so if you're powering over USB-C PD, check that it actually cuts that path too.

For suspend, cat /sys/power/state shows which sleep states the kernel on that image supports. If mem is listed, try rtcwake -m mem -s 120 and see whether it comes back. I haven't seen suspend documented for this board either way, so treat that as an experiment.

The 1970 date isn't what's stopping it, but if you want that RTC to keep time with power removed, the backup cell goes on JMISC pin 59 (3.3 V max).