- Last edited 5 months ago ago
How to use USB mass storage in U-Boot
This page explains how to use the U-Boot command
ums to update a SD card or e•MMC on the device.
1 ums command
In U-Boot, you can directly export the available block devices (sd/mmc/usb) such as USB mass storage devices with ums command:
help ums ums - Use the UMS [USB Mass Storage] Usage: ums <USB_controller> [<devtype>] <dev[:part]> e.g. ums 0 mmc 0 devtype defaults to mmc
See U-Boot documentation for details: usage/cmd/ums.html.
This U-Boot command
ums is infinite (a loop in USB treatments), and the U-Boot console is blocked until user enters a Ctrl-C.
2 Exporting a block device
On STMicroelectronics boards, the OTG USB controller device index is 0, SD card =
mmc 0 and, when available, e•MMC =
You can check the device connected on an SDMMC with the U-Boot command
mmc list and
mmc list STM32 SD/MMC: 0 (SD) STM32 SD/MMC: 1 (eMMC)
mmc info Device: STM32 SD/MMC Manufacturer ID: 3 OEM: 5344 Name: SS16G Bus Speed: 50000000 Mode: SD High Speed (50MHz) Rd Block Len: 512 SD version 3.0 High Capacity: Yes Capacity: 14.8 GiB Bus Width: 4-bit Erase Group Size: 512 Bytes
mmc dev 1 switch to partitions #1, OK mmc1 is current device
mmc info Device: STM32 SD/MMC Manufacturer ID: 11 OEM: 0 Name: 004GA0 Bus Speed: 52000000 Mode: MMC High Speed (52MHz) Rd Block Len: 512 MMC version 5.0 High Capacity: Yes Capacity: 3.7 GiB Bus Width: 8-bit Erase Group Size: 512 KiB HC WP Group Size: 4 MiB User Capacity: 3.7 GiB WRREL Boot Capacity: 2 MiB ENH RPMB Capacity: 512 KiB ENH Boot area 0 is not write protected Boot area 1 is not write protected
Then, execute one of the following commands:
Comments ums 0 mmc 0 --> start ums on SD card Ctrl-C
Comments ums 0 mmc 1 --> start ums on e•MMC Ctrl-C
You can also export a USB device connected to the USB host controller (USBH) =
Comments usb start --> start USB host controller ums 0 usb 0 --> start ums on USB device 0 (USB key for example) Ctrl-C usb stop --> stop USB host controller
After a delay (up to 15 seconds), the host sees the exported block device and you can use any command on the PC to access the partitions of the exported memory (dd, mount, cp, rsync). A Ctrl-C is needed to stop the command.
See also How to manually update bootloaders.