`power.deep_sleep()` without wake up sources does not go to sleep

[microbit-carlos]

This might be related to this CODAL issue:

• MakeCode power extension programme does not go to sleep  lancaster-university/codal-microbit-v2#203

However, based on the latest conversations with @JohnVidler we were thinking the issue might be in the MakeCode extension instead of CODAL.

However, in MicroPython executing power.deep_sleep() doesn't go to sleep either. Having a brief look the MicroPython code I can't see an obvious reason why it might not go to sleep if it's supported within CODAL itself:

micropython-microbit-v2/src/codal_port/modpower.c

Lines 54 to 109 in 2233d79

	STATIC mp_obj_t power_deep_sleep(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
	enum { ARG_ms, ARG_wake_on, ARG_run_every };
	static const mp_arg_t allowed_args[] = {
	{ MP_QSTR_ms, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
	{ MP_QSTR_wake_on, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_NONE} },
	{ MP_QSTR_run_every, MP_ARG_BOOL, {.u_bool = false} },
	};
	mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
	mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
	microbit_hal_power_clear_wake_sources();
	// Configure wake-up time, if given.
	bool wake_on_ms = false;
	uint32_t wake_ms = UINT32_MAX;
	if (args[ARG_ms].u_obj != mp_const_none) {
	wake_on_ms = true;
	wake_ms = mp_obj_get_int(args[ARG_ms].u_obj);
	}
	// Configure wake-up sources.
	mp_obj_t *items;
	size_t len = get_array(&args[ARG_wake_on].u_obj, &items);
	for (size_t i = 0; i < len; ++i) {
	const mp_obj_type_t *type = mp_obj_get_type(items[i]);
	if (microbit_obj_type_is_button(type)) {
	microbit_hal_power_wake_on_button(microbit_obj_get_button_id(items[i]), true);
	} else if (microbit_obj_type_is_pin(type)) {
	microbit_hal_power_wake_on_pin(microbit_obj_get_pin_name(items[i]), true);
	} else {
	mp_raise_ValueError(MP_ERROR_TEXT("expecting a pin or button"));
	}
	}
	// If run_every is true then check if any soft timers will expire and need to wake the device.
	if (args[ARG_run_every].u_bool) {
	microbit_soft_timer_set_pause(true);
	uint32_t ms = microbit_soft_timer_get_ms_to_next_expiry();
	if (ms != UINT32_MAX) {
	// A soft timer will expire in "ms" milliseconds.
	wake_on_ms = true;
	if (ms < wake_ms) {
	wake_ms = ms;
	}
	}
	}
	// Enter low power state.
	microbit_hal_power_deep_sleep(wake_on_ms, wake_ms);
	// Resume soft timer (doesn't hurt to resume even if it wasn't paused).
	microbit_soft_timer_set_pause(false);
	return mp_const_none;
	}

micropython-microbit-v2/src/codal_app/microbithal.cpp

Lines 130 to 136 in 6ea476f

	void microbit_hal_power_deep_sleep(bool wake_on_ms, uint32_t ms) {
	if (wake_on_ms) {
	uBit.power.deepSleep(ms, true);
	} else {
	uBit.power.deepSleep();
	}
	}

Example programme to replicate with MicroPython v2.1.0-beta.3:

from microbit import *
import power

while True:
    power.deep_sleep()
    display.show(Image.SURPRISED)
    sleep(500)

This always shows the SURPRISED face and doesn't go to sleep

[dpgeorge]

I think this is a "feature" of the CODAL: if there are no wake up sources configured, and no timeout, then the deepSleep() call returns immediately (presumably to prevent infinite waits that cannot be interrupted, requiring a reflash of the microbit to recover).

[dpgeorge]

We could fix this on the MicroPython side by just calling the CODAL deepSleep(ms, true) with a large timeout, and keep calling it in a loop forever.

[microbit-carlos]

This has been changed/fixed in the CODAL side in this PR, so we can just wait for the next tag to get the fix:

• Merging bug/deepsleep-anyway, feature/serial-wake and the hotfix all back into master lancaster-university/codal-microbit-v2#229

[microbit-carlos]

This is resolved in CODAL v0.2.43, we can close it when #132 is merged, or a different commit updates CODAL in the main branch.

[dpgeorge]

CODAL v0.2.43 is updated here.