Image upload over MCUBoot serial recovery not bootable

Question

Hi 
 I've an application running on nRF Conenct SDK 3.0.2 on an nRF52840DK. Now I tried to enable update support over serial recovery of MCUBoot using the USB ACM. 
 First I've setup sysbuild to use MCUboot in sysbuild.conf file: 
 # Enable bootloader with dedicated bootloader image SB_CONFIG_BOOTLOADER_MCUBOOT=y SB_CONFIG_MCUBOOT_MODE_SINGLE_APP=y 
 
 In the configuration for the mcuboot image (sysbuild/mcuboot/prj.conf) the following configuration was added: 
 
 CONFIG_PM=n 
 
 CONFIG_PM_PARTITION_SIZE_MCUBOOT=0x20000 
 
 CONFIG_MAIN_STACK_SIZE=10240 
 
 CONFIG_BOOT_SWAP_SAVE_ENCTLV=n 
 CONFIG_BOOT_ENCRYPT_IMAGE=n 
 
 CONFIG_BOOT_UPGRADE_ONLY=n 
 CONFIG_BOOT_BOOTSTRAP=n 
 
 ### mbedTLS has its own heap 
 # CONFIG_HEAP_MEM_POOL_SIZE is not set 
 
 ### We never want Zephyr's copy of tinycrypt. If tinycrypt is needed, 
 ### MCUboot has its own copy in tree. 
 # CONFIG_TINYCRYPT is not set 
 # CONFIG_TINYCRYPT_ECC_DSA is not set 
 # CONFIG_TINYCRYPT_SHA256 is not set 
 
 CONFIG_FLASH=y 
 CONFIG_FPROTECT=y 
 
 ### Various Zephyr boards enable features that we don't want. 
 # CONFIG_BT is not set 
 # CONFIG_BT_CTLR is not set 
 # CONFIG_I2C is not set 
 
 CONFIG_LOG=y 
 CONFIG_LOG_MODE_MINIMAL=y # former CONFIG_MODE_MINIMAL 
 ### Ensure Zephyr logging changes don't use more resources 
 CONFIG_LOG_DEFAULT_LEVEL=0 
 ### Use info log level by default 
 CONFIG_MCUBOOT_LOG_LEVEL_INF=y 
 ### Decrease footprint by ~4 KB in comparison to CBPRINTF_COMPLETE=y 
 CONFIG_CBPRINTF_NANO=y 
 ### Use the minimal C library to reduce flash usage 
 CONFIG_MINIMAL_LIBC=y 
 CONFIG_NRF_RTC_TIMER_USER_CHAN_COUNT=0 
 
 # NCS boot banner 
 CONFIG_NCS_APPLICATION_BOOT_BANNER_STRING="MCUboot" 
 
 # Partition table set by pm_static.yml 
 # CONFIG_PM_PARTITION_SIZE_MCUBOOT=0x20000 
 
 CONFIG_GPIO=y 
 
 CONFIG_SINGLE_APPLICATION_SLOT=y 
 # CONFIG_BOOT_SWAP_USING_MOVE=y 
 
 # Enable MCUboot Serial Recovery 
 CONFIG_MCUBOOT_SERIAL=y 
 CONFIG_BOOT_SERIAL_UART=y 
 CONFIG_UART_CONSOLE=n 
 
 # Point Serial Recovery to CDC_ACM 
 CONFIG_BOOT_SERIAL_CDC_ACM=y 
 
 # Enable Serial Recovery by Button 
 CONFIG_BOOT_SERIAL_WAIT_FOR_DFU=n 
 CONFIG_BOOT_SERIAL_ENTRANCE_GPIO=y 
 
 # USB configuration 
 CONFIG_USB_DEVICE_VID=0x1915 
 CONFIG_USB_DEVICE_PID=0x5300

By pressing the Button 1 on startup I'm able to enter the MCUBOOT serial revovery now. Also reading the image status work properly. But if I download the created "dfu_application.zip" file by using the newtmgr CLI client the system shows me on RTT log the there is no startable image found. Somehow the downloaded image is not startable. 
 
 Anyone had success with getting serial recovery with MCUBoot working? What could be wrong?

Håkon Alseth · Accepted Answer

Hi,

Glad to hear that this has improved the scenario.

The USB transport has a 64 byte EP, which means that increasing the MTU size will effectively send 'n' amount of packets of 64 bytes.

As you shared, there's two methods of improving speed:

1. increase mtu

2. decrease dwell-time between each requested MTU.

Adrian Eggenberger said:
I've one thing that is not working. We have own implementaiton for the serial number over USB. In the MCUboot at the moment we have the default USB serial number. How can I override weak methods (e.g. "usb_update_sn_string_descriptor" in my mcuboot image? All attempts I've made did not work.

The default behavior is that the function reads out the FICR.DEVICEID and applies this as the serial number:

https://github.com/nrfconnect/sdk-zephyr/blob/main/subsys/usb/device/usb_descriptor.c#L328-L355

I checked around with colleagues, and there is no straight-forward way to add a .c file to mcuboot without forking the repo.

So, I did an exercise to bend sysbuild a bit.

What you can do is to workaround this by treating your .c file as a out-of-tree driver specific to mcuboot.

Create sysbuild.cmake file containing:

set(mcuboot_EXTRA_ZEPHYR_MODULES "${CMAKE_CURRENT_LIST_DIR}/test_usb_sn_override" CACHE INTERNAL "test_module directory")

Then handle "test_usb_sn_override" as a out-of-tree directory by specifying test_usb_sn_override/zephyr/module.yml:

build:
  cmake: .
  kconfig: Kconfig

Then add a small conditional in test_usb_sn_override/CMakeLists.txt:

if(DEFINED CONFIG_BOOT_SERIAL_CDC_ACM)
    message("Adding override function for USB serial number")
    zephyr_library_sources(test.c)
endif()

Where test.c holds:

#include <zephyr/sys/byteorder.h>
#include <zephyr/sys/__assert.h>
#include <zephyr/usb/usb_device.h>

uint8_t *usb_update_sn_string_descriptor(void)
{
	/* SN is 16 bytes */
	static char hex[] = "CAFECAFECAFECAFE";
	return (uint8_t*)hex;
}

lsusb -d 2fe3:0100 -v

Bus 001 Device 042: ID 2fe3:0100 NordicSemiconductor MCUBOOT
Couldn't open device, some information will be missing
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               2.00
  bDeviceClass          239 Miscellaneous Device
  bDeviceSubClass         2 [unknown]
  bDeviceProtocol         1 Interface Association
  bMaxPacketSize0        64
  idVendor           0x2fe3 NordicSemiconductor
  idProduct          0x0100 MCUBOOT
  bcdDevice            4.00
  iManufacturer           1 ZEPHYR
  iProduct                2 MCUBOOT
  iSerial                 3 CAFECAFECAFECAFE
  ...

Here's a hello_world that does this:

hello_world_sysbuild_mcuboot_override_usb_sn2.zip

I used the nrf7002dk board for this exercise, so the board files in sysbuild/mcuboot/boards must be altered to match your chosen one.

PS: remove sysbuild.conf "SB_CONFIG_MCUBOOT_MODE_SINGLE_APP=y" if testing on nRF5340.

Kind regards,

Håkon

Image upload over MCUBoot serial recovery not bootable

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