External flash to sleep

[boris bergman1]

My board (nrf52840 sense) has flash memory P25Q16H. When I put everything off, the board consumes 25uA. To save the last bit of current I would like to put the flash memory to deep sleep.

	spi_flash_dev = DEVICE_DT_GET(DT_ALIAS(spi_flash0));	
	if (!device_is_ready(spi_flash_dev)) {
		LOG_ERR("%s: device not ready.\n", spi_flash_dev->name);
		return ENODEV;
	}
	
	if(pm_device_action_run(spi_flash_dev, PM_DEVICE_ACTION_SUSPEND)) { //only consumes more power, 3mA ?!
		LOG_ERR("could not suspend qspi flash device %s", spi_flash_dev->name);
	}

In the debugger, eventually this function in file nrf_qspi_nor.c is executed:

#ifdef CONFIG_PM_DEVICE
static int enter_dpd(const struct device *const dev)
{
	if (IS_ENABLED(DT_INST_PROP(0, has_dpd))) {
		struct qspi_cmd cmd = {
			.op_code = SPI_NOR_CMD_DPD,
		};
		uint32_t t_enter_dpd = DT_INST_PROP_OR(0, t_enter_dpd, 0);
		int rc;

		rc = qspi_send_cmd(dev, &cmd, false);
		if (rc < 0) {
			return rc;
		}

		if (t_enter_dpd) {
			uint32_t t_enter_dpd_us =
				DIV_ROUND_UP(t_enter_dpd, NSEC_PER_USEC);

			k_busy_wait(t_enter_dpd_us);
		}
	}

	return 0;
}
#endif /* CONFIG_PM_DEVICE */

SPI_NOR_CMD_DPD is indeed to 0xB9, which is consistent with the datasheet.

Problem: after executing this command, the power rises to 3.94mA. I have no idea what is causing this.

I'm running zephyr 3.5.99 ncs 2.6.1

[Vidar Berg]

Hi,

3.94mA could suggest that the CPU is prevented from entering sleep. Are you able to enable debug logging to see if there are any errors reported after calling pm_device_action_run()? 

Best regards,

Vidar

[boris bergman1]

No, it resides in low power state, executes a K_SLEEP()

cpu_idle.s

	 * For all the other ARM architectures that do not implement BASEPRI,
	 * PRIMASK is used as the interrupt locking mechanism, and it is not
	 * necessary to set PRIMASK here, as PRIMASK would have already been
	 * set by the caller as part of interrupt locking if necessary
	 * (i.e. if the caller sets _kernel.idle).
	 */
#endif /* CONFIG_ARMV7_M_ARMV8_M_MAINLINE */

	/* Enter low power state */
	_sleep_if_allowed wfi

	/*
	 * Clear PRIMASK and flush instruction buffer to immediately service
	 * the wake-up interrupt.
	 */
	cpsie	i
	isb

	bx	lr

[Vidar Berg]

So it is not going in a bootloop either? A debug log should make it apparent if that's the case.

[boris bergman1]

No it does not, it is also reachable with ble (yes when connecting +150uA)

Edit: I meant uA, not mA.

[Vidar Berg]

Thanks for confirming, but could you clarify what you mean by '+150 mA' when connecting? The nRF52840 can't draw that much current by itself. It would also be good if you could check whether the QSPI peripheral is be enabled when you measure the  ~4 mA after it the QSPI was supposed to be suspended. You can do so by reading the NRF_QSPI->ENABLE register.

[boris bergman1]

Vidar Berg said:

clarify what you mean by '+150 mA'

Sorry my mistake, meant uA.

I don't think I disabled QSPI, I just want to disable the flash device on the QSPI bus. I think indeed the flash device is using this much current, not the NRF52840, but I don't understand why. Thanks for your help anyway.

[Vidar Berg]

I know, but this was to help troubleshoot the problem. The PM suspend action will send the DPD command to the flash IC on the bus and then disable the QSPI peripheral afterward.