Zephyr / LittleFS intermittent mount issue on power cycle.

RE: Zephyr / LittleFS intermittent mount issue on power cycle.

Ryan010 — Wed, 16 Oct 2024 13:34:11 GMT

An update:

I am not certain that I have found the issue, but I did find some issues in my configuration, and application code that could have all contributed to this error.

Firstly, I confirmed that the power on ramp rate of the chip was in the valid range. VCC ramps up in 0.6ms. (within 100ms limit)

I then confirmed the delay to first read of the memory chip was OK - this is about 3ms (within the 20us limit of the external flash chip)

Then, I looked at my QSPI signaling, and something looked off. - clock is blue.

Turns out, I had forgotten to enable "high drive" for GPIO pins used for the QSPI interface in my custom board dtsi.

I included the nordic,drive-mode = <NRF_DRIVE_H0H1>; in the GPIO group, and the signaling looks great now, even with the added capacive load of my scope probe, measured after the series termination resistor.

qspi_default: qspi_default {
group1 {
psels = <NRF_PSEL(QSPI_SCK, 0, 19)>,
<NRF_PSEL(QSPI_IO0, 0, 22)>,
<NRF_PSEL(QSPI_IO1, 0, 21)>,
<NRF_PSEL(QSPI_IO2, 0, 23)>,
<NRF_PSEL(QSPI_IO3, 0, 20)>,
<NRF_PSEL(QSPI_CSN, 0, 17)>;

nordic,drive-mode = <NRF_DRIVE_H0H1>;
};
};

I caught another error - where the application code could trigger a write to the external memory while the power was failing:

Thankfully, the nRF is in control of the power off sequence, so I have blocked writes after the power down is triggered, for longer than the time required for VCC to drop below 1.8V.

I will continue testing this, but it is highly unlikely that the error will persist with the above corrections.

RE: Zephyr / LittleFS intermittent mount issue on power cycle.

Ryan010 — Tue, 15 Oct 2024 16:00:56 GMT

That is a great catch. Thank you! I've adjusted the clock speed.

I will test this, the intermittent nature may take some time to test well. I'll note the rise time of the VDD pin as well - confirming it falls within the 100ms maximum.

I'll test and update here as soon as I have something to report.

Thank you,
Ryan

RE: Zephyr / LittleFS intermittent mount issue on power cycle.

Edvin — Tue, 15 Oct 2024 13:05:57 GMT

Hello,

The first thing I noticed is that you say you are running the QSPI on 80MHz, but the QSPI on the nRF52840 only supports up to 32MHz. Can you please try to set it to 32MHz, and see if the behavior changes?

If that doesn't help, is this something you are able to reproduce on the nRF52840DK with the external chip that is present there?

Best regards,

Edvin