测试DFU时候,会生成并下载Bootloader Settings文件,以设置应用程序有效性,本文介绍Bootloader Settings文件的技术细节。
1. 基本信息
Bootloader Setting Page是指Bootloader工程开辟的一段Flash空间,其中保存了固件镜像的信息和DFU进度信息,这些信息称为Bootloader Settings。为了表述方便,Bootloader Settings Page或Bootloader Settings都简称为Settings。
对于nRF52系列芯片,Settings的位置如下图:

nRF52832芯片的Flash大小为512 kB(0x0008 0000),Settings位于最顶端(0x0007 F000 – 0x0008 0000),大小为1 Page(4 kB)。
知道了Settings的位置,即可通过nrfjprog --readcode flash.hex
读出芯片Flash数据,然后定位到0x0007 F000处读取Settings内容。
在Settings的下方是MBR Param Storage,它的长度也是4 kB,地址为:0x0007 E000 – 0x0007 F000。这块区域用于存放Settings的备份。
从infocenter上得知,Bootloader Settings信息包含以下内容:
- current firmware – size, CRC-32
- pending firmware – size, CRC-32
- progress of the firmware update
- progress of the firmware activation
- current firmware versions (application and bootloader)
- transport-specific data
正常执行DFU升级过程中,Bootloader接收固件镜像并会自动计算这些信息,然后写入Flash。
也可以利用固件镜像app.hex手动生成Settings文件(settings.hex),命令如下:
nrfutil settings generate --family NRF52 --no-backup --application app.hex --application-version 0x01 --bootloader-version 0x01 --bl-settings-version 0x02 settings.hex
–no-backup表示不使用备份区域,对于SDK 12.0 ~ SDK 15.0,应该使用该参数以实现兼容性,对于SDK 15.1以上版本,应该忽略该参数。如果不使用该参数,则会在MBR Param Storage区域内保存Settings Page的副本,生成的settings.hex中能够看到0x7E000 – 0x7F000 的内容与0x7F000 – 0x80000的内容相同。如果使用该参数,则不保存备份副本,settings.hex中也没有0x7E000 – 0x7F000的内容。
–bl-settings-version只有两个可选项:0x01和0x02。对于SDK 12.3 ~ SDK 15.2,应该使用0x01,对于SDK 15.3应该使用0x02。如果使用0x02,会在Settings信息中引入 boot_validataion_crc等信息,这些额外的数据导致两个版本不兼容。具体差异其实很简单,打开bl_dfu_sett.py文件,找到BLDFUSettingsStructV2 与 BLDFUSettingsStructV1的类定义,一看便知。
更多的内容请参考官方文档:https://github.com/nordicsemiconductor/pc-nrfutil。
使用以下命令查看Settings.hex的内容:
nrfutil settings display settings.hex
Settings.hex 的内容形式如下:
Bootloader DFU Settings:
* File: settings.hex
* Family: nRF52
* Start Address: 0x0007E000
* CRC: 0x740EFA00
* Settings Version: 0x00000002 (2)
* App Version: 0x00000001 (1)
* Bootloader Version: 0x00000001 (1)
* Bank Layout: 0x00000000
* Current Bank: 0x00000000
* Application Size: 0x0000EC84 (60548 bytes)
* Application CRC: 0x9B8FC175
* Bank0 Bank Code: 0x00000001
* Softdevice Size: 0x00000000 (0 bytes)
* Boot Validation CRC: 0xD0E62C99
* SD Boot Validation Type: 0x00000000 (0)
* App Boot Validation Type: 0x00000001 (1)
用文本工具打开Settings.hex文件,其内容如下:
:020000040007F3
:10F0000000FA0E7402000000010000000100000080
:10F01000000000000000000084EC000075C18F9B20
:10F0200001000000000000000000000000000000DF
:10F0300000000000000000000000000000000000D0
:10F0400000000000000000000000000000000000C0
:10F0500000000000000000000000000000000000B0
:10F0600000000000000000000000000000000000A0
:10F070000000000000000000000000000000000090
:10F080000000000000000000000000000000000080
:10F090000000000000000000000000000000000070
:10F0A0000000000000000000000000000000000060
:10F0B0000000000000000000000000000000000050
:10F0C0000000000000000000000000000000000040
:10F0D0000000000000000000000000000000000030
:10F0E0000000000000000000000000000000000020
:10F0F0000000000000000000000000000000000010
:10F1000000000000000000000000000000000000FF
:10F1100000000000000000000000000000000000EF
:10F1200000000000000000000000000000000000DF
:10F1300000000000000000000000000000000000CF
:10F1400000000000000000000000000000000000BF
:10F1500000000000000000000000000000000000AF
:10F16000000000000000000000000000000000009F
:10F17000000000000000000000000000000000008F
:10F18000000000000000000000000000000000007F
:10F19000000000000000000000000000000000006F
:10F1A000000000000000000000000000000000005F
:10F1B000000000000000000000000000000000004F
:10F1C000000000000000000000000000000000003F
:10F1D000000000000000000000000000000000002F
:10F1E000000000000000000000000000000000001F
:10F1F000000000000000000000000000000000000F
:10F2000000000000000000000000000000000000FE
:10F2100000000000000000000000000000000000EE
:10F2200000000000000000000000000000000000DE
:10F2300000000000000000000000000000000000CE
:10F2400000000000000000000000000000000000BE
:10F25000000000000000000000000000992CE6D033
:10F26000000000000000000000000000000000009E
:10F27000000000000000000000000000000000008E
:10F28000000000000000000000000000000000007E
:10F29000000000000000000000000000000000006E
:10F2A000000175C18F9B00000000000000000000FD
:10F2B000000000000000000000000000000000004E
:10F2C000000000000000000000000000000000003E
:10F2D000000000000000000000000000000000002E
:10F2E000000000000000000000000000000000001E
:10F2F000000000000000000000000000000000000E
:10F3000000000000000000000000000000000000FD
:10F3100000000000000000000000000000000000ED
:03F32000000000EA
:00000001FF
Intel hex文件的格式解析请参考:https://en.wikipedia.org/wiki/Intel_HEX 。
第一行为地址偏移,偏移量为0x0007,所以第二行的实际地址为0x0007 F000,这正是Settings的Flash起始地址。
倒数第二行为数据末尾行,可知数据总量为0xF322 + 1 = 803,即Settings.hex 的有效数据总数是803。
有效数据的排列顺序根据BLDFUSettingsStructV2 的定义而来, BLDFUSettingsStructV2 的内容如下:
def __init__(self, settings_address):
self.bytes_count = 803 # Entire settings page
self.crc = settings_address + 0x0
self.sett_ver = settings_address + 0x4
self.app_ver = settings_address + 0x8
self.bl_ver = settings_address + 0xC
self.bank_layout = settings_address + 0x10
self.bank_current = settings_address + 0x14
self.bank0_img_sz = settings_address + 0x18
self.bank0_img_crc = settings_address + 0x1C
self.bank0_bank_code = settings_address + 0x20
self.sd_sz = settings_address + 0x34
self.init_cmd = settings_address + 0x5C
self.boot_validataion_crc = settings_address + 0x25C
self.sd_validation_type = settings_address + 0x260
self.sd_validation_bytes = settings_address + 0x261
self.app_validation_type = settings_address + 0x2A1
self.app_validation_bytes = settings_address + 0x2A2
self.last_addr = settings_address + 0x322
首先看到bytes_count=803,这与上面的计算一致。
第一个字段为CRC,本文中CRC为0x740EFA00,换成Little Endian后为
00 FA 0E 74。紧挨着下一个字段的偏移地址为4,所以本字段大小为4字节。
第二个字段为Sett_ver,本文中该值为1,通过下个字段的偏移量得知Sett_ver长度也是4。
以此类推,可以分析大多数字段。
找到sd_sz,该字段与上一字段之间差距为20字节,并不是bank0_bank_code长度是20字节,而是这之间还填充了两个字段:bank1 {img_sz, img_crc, bank_code}和write_offset,二者共16字节,加上bank0_bank_code 所占4字节,共20字节。
bank1与write_offset定义在Bootloader工程中的nrf_dfu_bytes.h -> nrf_dfu_settings_t结构体中。
打开nrf_dfu_settings_t的定义:
typedef struct
{
uint32_t crc;
uint32_t settings_version;
uint32_t app_version;
uint32_t bootloader_version;
uint32_t bank_layout;
uint32_t bank_current;
nrf_dfu_bank_t bank_0;
nrf_dfu_bank_t bank_1;
uint32_t write_offset;
uint32_t sd_size;
dfu_progress_t progress;
uint32_t enter_buttonless_dfu;
uint8_t init_command[INIT_COMMAND_MAX_SIZE];
uint32_t boot_validation_crc;
boot_validation_t boot_validation_softdevice;
boot_validation_t boot_validation_app;
boot_validation_t boot_validation_bootloader;
nrf_dfu_peer_data_t peer_data;
nrf_dfu_adv_name_t adv_name;
} nrf_dfu_settings_t;
它与上面的 BLDFUSettingsStructV2 基本对应。
观察init_command,它是一个数组,数组长度为512!init_command 的内容请参考上一篇文章“弄懂Init Packet”。
再观察BLDFUSettingsStructV2的init_cmd与boot_validataion_crc的偏移量,二者之差恰好等于512。
后面四个字段与Validation有关,通常不专门设置。值得注意的是,默认情况下,app_validation_type=1,app_validation_bytes=bank0_img_crc,所以在hex文件中看到了一个75C18F9B。
至此,我们完整的分析了Settings.hex 的内容细节。
Bootloader启动时候,会检查Settings中以下信息:
- bank0_bank_code
- bank0_img_crc
如果二者都正确,则执行跳转进入Application,否则驻留在Bootloader中执行DFU。
(完)
写得真好!!!