External SPI Flash Bootloader on nRF52 Series

This blog is to demo how to use the external SPI flash for Device Firmware Upgrade (DFU) on the nRF52 Series. The target is to minimize the size of the bootloader particular on the nRF52810. The total size of the bootloader + its setting is only 12KB comparing to original bootloader SDK (32KB).

Note: this example is only target to upgrade the application firmware.

In the Nordic SDK, it supports two difference DFU.

  1. Bootloader with BLE for Over the Air Upgrade
  2. Bootloader with Serial UART

Memory Layout

When adding a bootloader to your device, you must be aware of where in the device memory the different firmware components are located.

The following table shows the memory layout for the different chips with current SoftDevices:

UsageMemory range nRF52832 (S132 v6.1.x)Memory range nRF52840 (S140 v6.1.x)Memory range nRF52810 (S112 v6.1.x)
Bootloader settings0x0007 F000 – 0x0008 0000 (4 kB)0x000F F000 – 0x0010 0000 (4 kB)0x0002 F000 – 0x0003 0000 (4 kB)
MBR parameter storage0x0007 E000 – 0x0007 F000 (4 kB)0x000F E000 – 0x000F F000 (4 kB)0x0002 E000 – 0x0002 F000 (4 kB)
Bootloader0x0007 8000 – 0x0007 E000 (24 kB)0x000F 8000 – 0x000F E000 (24 kB)0x0002 8000 – 0x0002 E000 (24 kB)
Application area (incl. free space)0x0002 6000 – 0x0007 8000 (328 kB)0x0002 6000 – 0x000F 8000 (840 kB)0x0001 9000 – 0x0002 8000 (60 kB)
SoftDevice0x0000 1000 – 0x0002 6000 (148 kB)0x0000 1000 – 0x0002 6000 (148 kB)0x0000 1000 – 0x0001 9000 (96 kB)
Master Boot Record (MBR)0x0000 0000 – 0x0000 1000 (4 kB)0x0000 0000 – 0x0000 1000 (4 kB)0x0000 0000 – 0x0000 1000 (4 kB)

The maximum size of the application layer is 60KB if using the nRF52810 with S112v6.1.x.

Proposal (External SPI Flash for DFU)

The size of the bootloader with SPI data flash (DFU) is reduced from 24KB to 8KB. Thus, the maximum size of application if using S112v5.1 can be increased up to 84KB.

If the device requires the pairing / bonding feature, it needs to reserve at least 2 extra pages for storing bonding information. The size of application region would be reduced to 84KB – 8KB (2 page) = 76KB.

UsageMemory range nRF52810 (S112 v5.1.x)Memory range nRF52810 (S112 v6.1.x)
Bootloader settings0x0002 F000 – 0x0003 0000 (4 kB)0x0002 F000 – 0x0003 0000 (4 kB)
Bootloader0x0002 C000 – 0x0002 F000 (8 kB)0x0002 C000 – 0x0002 F000 (8 kB)
Application area (incl. free space)0x0001 8000 – 0x0002 C000 (84 kB)0x0001 9000 – 0x0002 C000 (80 kB)
SoftDevice0x0000 1000 – 0x0001 8000 (92 kB)0x0000 1000 – 0x0001 9000 (96 kB)
Master Boot Record (MBR)0x0000 0000 – 0x0000 1000 (4 kB)0x0000 0000 – 0x0000 1000 (4 kB)

I use the NRF52840 DK board and configure the on-board QSPI to act as external SPI data flash in this demo.

In the example code, two individual application images are stored at the external SPI flash. The 2nd image is used as the default (backup) one. The bootloader would copy the default FW to the application region, if the application region is corrupted or blank (CRC check result is invalid). On the other hand, it would use the 1st FW for updating the application region.

Also, this example spi bootloader is independent from the SDK version. It means that it can work with difference Nordic SDK version.

Testing Procedure

Step 1

  • Compile and link to 2 difference firmware hex file.

Step 2

  • Modify the starting address of 2 difference firmware address on the SPI flash inside bootloader.
#define APP_CFG_INIT_START_ADDR  0x00000000

#define APP_CFG_FW_START_ADDR  0x00001000

define APP_CFG_INIT_START_ADDR2  0x00020000

#define APP_CFG_FW_START_ADDR2  0x00021000

For example,

The address of 1st application firmware is 0x00001000. Its configuration init file is at 0x00000000. (ble_app_test1)

The address of 2nd application firmware is 0x00021000. Its configuration init file is at 0x00020000. (ble_app_test2)

Step 3

  • Generate the corresponding init (configure file) on each FW (HEX) by modified nrfutil.
nrfutil_spi pkg generate --hw-version 52 --application-version 1 --application ble_app_test_pca10056_s140.hex --sd-req 0xAE 840_slim_spi_test.zip
nrfutil_spi pkg generate --hw-version 52 --application-version 1 --application ble_app_test2_pca10056_s140.hex --sd-req 0xAE 840_slim_spi_test2.zip

The format of the init configure file is

WORDData field length = 16
WORDFirmware version
WORDFirmware size
WORDFirmware CRC-32
WORDCRC-32 for the 12-byte data

Step 4

  • Program the init and hex firmware on the nRF52840 DK board through nrfjprog.
objcopy -v -I binary -O ihex --change-addresses 0x12000000 ble_app_test_pca10056_s140.dat init_pkt.hex 
objcopy -v -I binary -O ihex --change-addresses 0x12001000 ble_app_test_pca10056_s140.bin   fw_bin.hex

objcopy -v -I binary -O ihex --change-addresses 0x12020000 ble_app_test_pca10056_s140.dat init_pkt_2.hex 
objcopy -v -I binary -O ihex --change-addresses 0x12021000 ble_app_test_pca10056_s140.bin   fw_bin_2.hex

nrfjprog -f nrf52 --qspicustominit --qspieraseall

nrfjprog -f nrf52 --qspicustominit --program init_pkt.hex 
nrfjprog -f nrf52 --qspicustominit --program fw_bin.hex

Because the address of the QSPI is offset by 0x12000000. It should be equivalent to 0x00000000 (SPI flash address).

Requirement

  • NRF52840 DK board
  • SDK 15.2 / SDK 15.3
  • IDE: Segger Embedded Studio

The materials are placed at (https://github.com/jimmywong2003/nrf5-external-spi-flash-bootloader/).

10 thoughts on “External SPI Flash Bootloader on nRF52 Series

  1. When someone writes an post he/she maintains the idea of
    a user in his/her brain that how a user can understand
    it. So that’s why this article is outstdanding. Thanks!

    Like

    1. This demo is to show how to upgrade the application firmware from spi flash only. It does’t cover how to store the firmware to external flash.

      Like

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