How to save environment variables in UBoot for SD card?

Sean Machin

I was under the impression that the file uEnv.txt in the first DOS partition of the SD card could be used to define environment variables for U-Boot. However my definitions in there are not being recognized. There's a trace of my U-Boot startup log below. How do I get the reading of environment variables fro, uEnv.txt to work? My U-Boot version is U-Boot 2012.10-svn49326.

NAND: No NAND device found!!!
0 MiB
MMC: OMAP SD/MMC: 0, OMAP SD/MMC: 1
*** Warning - readenv() failed, using default environment

musb-hdrc: ConfigData=0xde (UTMI-8, dyn FIFOs, bulk combine, bulk split, HB-ISO Rx, HB-ISO Tx, SoftConn)
musb-hdrc: MHDRC RTL version 2.0
musb-hdrc: setup fifo_mode 4
musb-hdrc: 28/31 max ep, 16384/16384 memory
USB Peripheral mode controller at 47401000 using PIO, IRQ 0
musb-hdrc: ConfigData=0xde (UTMI-8, dyn FIFOs, bulk combine, bulk split, HB-ISO Rx, HB-ISO Tx, SoftConn)
musb-hdrc: MHDRC RTL version 2.0
musb-hdrc: setup fifo_mode 4
musb-hdrc: 28/31 max ep, 16384/16384 memory
USB Host mode controller at 47401800 using PIO, IRQ 0

over 11 years ago

0 Miroslav Kiradzhiyski XID over 11 years ago

TI__Mastermind 25235 points

Hi Sean,

This message is the result of not having a NAND device.

The U-Boot always tries to load its environment from the NAND dedicated area (NAND offset 0x260000) and since there is no NAND chip on your board it fails.

The uEnv.txt file on the /boot partition of your SD card comes into play a bit later when the "bootcmd" is executed.

You can check what the "bootcmd" does in U-Boot by typing "print" in the U-Boot prompt.

Best regards,
Miroslav

0 Sean Machin over 11 years ago in reply to Miroslav Kiradzhiyski XID

Intellectual 995 points

Thanks for the response. You are correct, I just checked and boot (which uses bootcmd) does load the variables from uEnv.txt. However, I thought the whole point of that file was to store environment variables for U-Boot itself? If it's not read until we're booting the kernel that what use is it?