GD25WB256 Alternative + Firmware Changes (nRF9151 External Flash)

[Akshay]

Hi,

I’m using GD25WB256 as external flash on nRF9151 for MCUboot secondary slot. It’s currently not available from our supplier, so I’m looking for alternatives.

Current overlay:

/ {
    chosen {
        nordic,pm-ext-flash = &gd25wb256;
    };
};

&gd25wb256 {
    status = "okay";
};

Questions:

1. What are good 256Mbit SPI NOR alternatives (preferably 1.8V) that work well with nRF Connect SDK + MCUboot?
   • Considering Winbond / ISSI / Macronix parts
2. For replacing the flash, is it enough to:
   • Just update the device tree (JEDEC ID, size)
   • Keep everything else unchanged?
3. Anything to watch out for (4-byte addressing, SFDP, etc.)?

Thanks!

[Hung Bui]

Hi Akshay, 

We won't be able to give you a specific recommendation for an alternative to GD25WB256. The NCS SDK is highly agnostic to a specific flash chip. Any modern QSPI flash will be "plug-and-play" once you update the JEDEC ID and size in your Devicetree. We are not supposed to give any "favorite" flash chip/ manufacturer that you should use. 

As far as I know, you just need to use the correct JDEC ID and correct size in the device tree overlay you should be fine. 

Anything to watch out for (4-byte addressing, SFDP, etc.)?

Not that I'm aware of, AFAIK you just need enter-4byte-addr = <0x01>;     defined in the device tree overlay.

[Akshay]

Hi Hung,

We decided to use the 3 V SPI NOR flash from Winbond, the W25Q256JV, as an external flash for the nRF9151.

Below are the relevant schematics and firmware configuration.

Hardware:

• SPI3 used for the flash
• CS connected to the dedicated SPI CS line
• HOLD#/RESET and WP#/IO2 are pulled up to VCC using 10 kΩ resistors
• VCC = 3.0 V
• Decoupling capacitor: 100 nF close to the flash
• SPI signals routed directly from the nRF9151

Device tree configuration:

&spi3 {
    status = "okay";

    w25q256: w25q256jv@1 {
        compatible = "jedec,spi-nor";
        status = "okay";
        reg = <1>;

        spi-max-frequency = <8000000>;
        jedec-id = [ef 70 19];
        size = <268435456>;

        sfdp-bfp = [
            e5 20 f3 ff  ff ff ff 0f  44 eb 08 6b  08 3b 42 bb
            ee ff ff ff  ff ff 00 ff  ff ff 00 ff  0c 20 0f 52
            10 d8 00 ff  44 7a c9 fe  83 67 26 62  ec 82 18 44
            7a 75 7a 75  04 c4 d5 5c  00 06 74 00  08 50 00 01
        ];

        //sfdp-bfp = [];

        has-dpd;
        t-enter-dpd = <3000>;
        t-exit-dpd = <40000>;

        /* Required for 256 Mbit */
        enter-4byte-addr = <0x01>;
    };
};

chosen {
    nordic,pm-ext-flash = &w25q256;
};

Kconfig:

CONFIG_SPI_NOR_SFDP_RUNTIME=y

Since I do not know the correct sfdp-bfp values for the W25Q256JV, I initially copied the values from the GD25WB256. However, I am expecting the driver to read the SFDP dynamically at runtime because CONFIG_SPI_NOR_SFDP_RUNTIME=y is enabled.

Unfortunately, this is not working.

Could you please verify:

1. Whether the hardware schematic connections look correct for the W25Q256JV
2. Whether the device tree configuration is correct
3. Whether CONFIG_SPI_NOR_SFDP_RUNTIME=y should completely eliminate the need for sfdp-bfp
4. Whether the enter-4byte-addr = <0x01>; configuration is correct for this flash
5. If there are any additional requirements for using the W25Q256JV with the nRF9151 external flash / PM subsystem.

Thanks,