Boot Loader. Bootloader

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Stewart Boyd
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1 October 2013

2 Boot Loader A program that is executed upon initial power-up that typically involves a power-on self-test, locating and initializing peripheral devices, and then loading and starting an operating system. Bootloader A program that is used to facilitate updating a target device s application program without the use of any special or additional hardware connection. Typical functions include: Serial communications with a host via UART, USB, Ethernet, CAN, SPI, I2C, etc. Erasing, programming and verifying non-volatile memory (i.e., Flash). 2

3 Upgrading a device s application software after it has been shipped i.e., field upgrade Bug fixes Feature enhancement The Internet of Things As more devices be come more connected, there is a growing need to be able to perform application software repair and/or enhancement. 3

4 There are many different types and styles of Bootloaders. In addition to the variety of serial communication resources, there are diverse expectations regarding the Bootloader functional capabilities. Image Verification Multiple Image Management Erase and Reprogram Checksum/CRC UART or USB or Ethernet or CAN or SPI or I2C 4

5 Primarily via application notes, such as: AN2295 : Developer's Serial Bootloader for M68HC08, HCS08, ColdFire, and Kinetis MCUs AN4367 : Ethernet Bootloader for MCU AN4368 : USB Mass Storage Device Host Bootloader AN4370 : USB Device Firmware Update Bootloader for MCUs AN4379 : Freescale USB Mass Storage Device Bootloader AN4605 : Secure Bootloader Implementation 5

6 A truly Universal Bootloader isn t very practical. There are simply too many options to consider. Supporting all permutations would result in a Bootloader footprint that would very likely be too large to be usable. But a Unified Bootloader is considerably more viable. Target a specific MCU family and support the on-chip serial communication resources. Provide a reasonable list of commands and capabilities. The designer of a Bootloader must have intimate knowledge of the target MCU s architecture, including Flash programming algorithms. 6

7 0x0000_0000 Vector Table VTOR Vector Table Offset Register k to 256k bytes Flash Upon Power-On Reset, VTOR = 0x0000_0000 (i.e., TBLOFF = 0) Using VTOR, the Vector Table can be relocated to any 128-byte boundary address VTOR + 0x00 VTOR + 0x04 0x0000_0000 0x0000_0400 0x0000_0800 0x0000_0C00 0x0000_1000 0x0000_1400 0x0000_1800 0x0000_1C00 Power-On Reset 0x0000_0000 0x0000_0004 TBLOFF The Flash memory Erase Sector size is 1k bytes: Vector Table Initial Stack Pointer Initial Program Counter Flash Configuration Field 0x0000_0400 0x0000_0401 0x0000_0402 0x0000_0403 0x0000_0404 0x0000_0405 0x0000_0406 0x0000_0407 0x0000_0408 0x0000_0409 0x0000_040A 0x0000_040B 0x0000_040C 0x0000_040D 0x0000_040E 0x0000_040F Backdoor Comparison Key Program Flash Protection Bytes Flash Security Byte (FSEC) Flash Nonvolatile Option Byte (FOPT) reserved reserved

8 1k bytes 0x0000_0000 0x0000_0400 Vector Table Bootloader Config Bootloader VTOR Program Flash Protection Registers Flash Configuration Field 0x0000_040B FPROT0 0x0000_040A FPROT1 0x0000_0409 FPROT2 0x0000_0408 FPROT3 8k to 256k bytes Flash Application Code 0 Program Flash region is protected 1 Program Flash region is not protected (default erased value) 0x0000_0000 Last Program Flash Address Program Flash Size 32 Program Flash Size 32 Program Flash Size 32 Program Flash Size 32 Program Flash Size 32 Program Flash Size 32 Program Flash Size 32 Program Flash Size 32 FPROT3[0] FPROT3[1] FPROT3[2] FPROT3[3] FPROT0[4] FPROT0[5] FPROT0[6] FPROT0[7] 8k Flash : 1k per region (FPROT3 only) 16k Flash : 1k per region (FPROT3 & FPROT2 only) 32k Flash : 1k per region 64k Flash : 2k per region 128k Flash : 4k per region 256k Flash : 8k per region Smallest Protection Region Size is equal to the Erase Sector Size (i.e., 1k bytes) The Reset Vector must be Protected from accidental erasure The Flash Configuration Field must be Protected from accidental erasure The Bootloader must be Protected from accidental erasure 8

9 0x0000_0000 Power-On Reset Vector Table Bootloader Config Bootloader VTOR Protected Power-On Reset Vector Table Initialize Bootloader 8k to 256k bytes Flash Application Code Application Reset Valid Application Program? Y Modify VTOR N Execute Bootloader Execute Application The Reset Vector must be Protected from accidental erasure The Flash Configuration Field must be Protected from accidental erasure The Bootloader must be Protected from accidental erasure 9

10 0x0000_0000 Power-On Reset Vector Table Bootloader Config VTOR Protected Power-On Reset Vector Table Initialize Bootloader 8k to 256k bytes Flash Application Code Application Reset Valid Application Program? Y Modify VTOR N Execute Bootloader Execute Application Bootloader The Reset Vector must be Protected from accidental erasure The Flash Configuration Field must be Protected from accidental erasure The Bootloader must be Protected from accidental erasure 10

the BSD three clause license Standard set of peripherals UART with autobaud USB device HID

11 Common Bootloader for all Kinetis devices Will be placed into ROM on new Kinetis MCUs Can reside in Flash Will be available as source code for possible customization Licensed with the BSD three clause license Standard set of peripherals UART with autobaud USB device HID class I2C slave SPI slave One Unified Bootloader for all the Kinetis Cortex M0+, M4 Families! 11

12 ROM Flashloader Bootloader Present in upcoming Kinetis parts Bootable via external pin or flash options Configurable via parameters in flash Callable by customer application Factory programmed into Kinetis devices without ROM Intended for manufacturing Copies itself to RAM and programs entire flash array Flash resident, alongside customer application Intended for field updates Callable by customer application 12

13 blhost command line tool Sends individual bootloader commands Supports all standard peripherals Example GUI firmware updater application Supported operating systems Windows Mac (Planned) Linux (Planned) 13

14 ./BLHOST 14

15 Uses command-based protocol Common commands for all MCUs Common command protocol for all peripherals UART, I2C, SPI wrapped in framing protocol Provides flow control and error detection for all ACK, NAK (retry), CRC16 USB HID custom reports Hardware provides flow control and error detection 15

16 Flash erase all Flash erase region Read memory** Write memory Fill memory** Flash security disable Uses backdoor key Execute Call Reset ReceiveSBFile** GetProperty SetProperty** Memory commands work on flash, RAM, and peripheral registers** Memory is not readable if flash security is enabled. Certain SB Commands will support security on the Kinetis K (Cortex M4) **Reserved for larger configurations of the bootloader 16

17 Encapsulated programming image format (K-Series) will support Encryption AES 128k Contains all commands required to program a customer application Downloadable to bootloader with a single command Generated with open-source elftosb tool Supports ELF, S19, binary, etc input files Format supports security features like encryption (for future devices) 17

18 Application image CRC start, count, expected value Enabled peripherals bit mask Clock high speed flag and dividers I2C slave address USB VID/PID and pointer to USB strings Active peripheral detection timeout (jump to application) 18

Bootloader Solution for Kinetis MCUs

Bootloader Solution for Kinetis MCUs APF-SDS-T0108 Michael Norman Freescale Technical Marketing Manager Chris Reed Freescale MCU Software Architect J U N E. 2 0 1 4 TM External Use Lecture and Demo: Bootloader