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For the full list of driver parameters available in the device tree, refer to https://docs.zephyrproject.org/latest/build/dts/api/bindings/mtd/jedec%2Cspi-nor.html#std-dtcompatible-jedec-spi-nor
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2. Support for QSPI Flash
Note that the jedec,spi-nor driver runs on top of the SPI driver, so the DSPI and QSPI features are not supported by this solution. For some Nordic chips (nRF5340 in particular), there is a nordic,qspi-nor driver that supports operating in QSPI mode, with its own set of flash parameters. nordic,qspi-nor is not affected by SPI_NOR_SFDP, all required parameters need to be supplied in the device tree node.
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3. Software APIs
There are several API levels that allow access to SPI Flash.
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3.1. Low Level Flash Access
This level can be used to access SPI Flash as a raw Flash device.
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There are also the zephyr/samples/drivers/jesd216 and zephyr/samples/drivers/spi_flash demos that demonstrate use of low-level API.
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3.2. Flash Partitioning
Zephyr additionally has API’s that can be used to partition SPI Flash. The goal is to provide a facility to split a single Flash device into several named areas to be used independently and preventing out-of-bounds access.
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The zephyr/samples/subsys/fs/littlefs sample illustrates use of a fixed partition to create a file system over it. mcuboot is another useful example.
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3.3. High-Level Non-Volatile API
There are several high-level storage API’s provided by Zephyr that can be used over Flash (or a Flash area):
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In the nrf-app application use the CONFIG_PM_PARTITION_REGION_LITTLEFS_EXTERNAL, CONFIG_PM_PARTITION_REGION_SETTINGS_STORAGE_EXTERNAL, and CONFIG_PM_PARTITION_REGION_NVS_STORAGE_EXTERNAL to relocate corresponding partition to SPI Flash.
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4. Zephyr Shell Commands
The nrf-app application comes preconfigured to use SPI Flash, with support for the relevant Zephyr shell commands enabled. The following shell commands are available:
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Run a generic erase/write/read/compare test:
Code Block uart:~$ flash test gd25wb256e3ir@1 0 0x4000 1 Erase OK. Write OK. Verified OK. Erase-Write-Verify test done.
Run read and write measurements:
Code Block uart:~$ flash erase gd25wb256e3ir@1 0 0x4000 Erase success. uart:~$ flash write_test gd25wb256e3ir@1 0 0x4000 1 Loop #1 done in 53 ticks. Total: 53ms, Per loop: ~53ms, Speed: ~301.9KiBps uart:~$ flash read_test gd25wb256e3ir@1 0 0x4000 1 Loop #1 done in 16ms. Total: 16ms, Per loop: ~16ms, Speed: ~1000.0KiBps
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5. Configuring for a Different SPI Flash Device
This chapter explains how to configure a different Flash device. Specifically, the GD25WB256E Flash device installed on the Thingy-9151-Lite platform is used as an example.
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5.1. Get JEDEC info
First step when setting a new SPI Flash is to obtain information about it. To do so, we need to create a minimally required description of the Flash. Let’s start with the following overlay:
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| Code Block |
|---|
/* Deactivate predefined flash node for SPI flash installed on DK */
&gd25wb256 {
status = "disable";
};
&arduino_spi {
/* Insert node for new device */
newspi: newdevice@1 {
compatible = "jedec,spi-nor";
status = "ok";
reg = <1>;
spi-max-frequency = <8000000>;
jedec-id = [c8 65 19];
size = <268435456>;
has-dpd;
t-enter-dpd = <3000>;
t-exit-dpd = <40000>;
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
];
};
};
/* Use new device in choosen and aliases */
/ {
chosen {
nordic,pm-ext-flash = &newspi;
};
aliases {
spi-flash0 = &newspi;
ext-flash = &newspi;
};
}; |
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5.2. Configuring for different SPI flash device with QSPI support on nRF5340 (nordic,qspi-nor)
The nRF5340 MCU includes a QSPI controller that allows to use faster flash devices in dual and quad SPI mode.
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