Hi @dzhou, that was a little painful, but i also got it working:
Using v2020.10-rc3 of https://github.com/u-boot/u-boot with the default am335x_evm_defconfig so no changes required.
On Debian install:
sudo apt install picocom lrzsz
Verify board is sending a string of “CCC’s”…
Un-power board, make sure it’s powered down
Start Picocom:
picocom -b 115200 /dev/ttyUSB0 --send-cmd "sx -vv"
In picocom, Press CTRL+A; CTRL+S; transfer u-boot-spl.bin from u-boot/spl/
Plug in/power board, and wait for transfer to complete:
Press CTRL+A; CTRL+S; transfer u-boot.img
picocom -b 115200 /dev/ttyUSB0 --send-cmd "sx -vv"
picocom v3.1
port is : /dev/ttyUSB0
flowcontrol : none
baudrate is : 115200
parity is : none
databits are : 8
stopbits are : 1
escape is : C-a
local echo is : no
noinit is : no
noreset is : no
hangup is : no
nolock is : no
send_cmd is : sx -vv
receive_cmd is : rz -vv -E
imap is :
omap is :
emap is : crcrlf,delbs,
logfile is : none
initstring : none
exit_after is : not set
exit is : no
Type [C-a] [C-h] to see available commands
Terminal ready
*** file: u-boot-spl.bin
$ sx -vv u-boot-spl.bin
Sending u-boot-spl.bin, 848 blocks: Give your local XMODEM receive command now.
Bytes Sent: 108672 BPS:6882
Transfer complete
*** exit status: 0 ***
U-Boot SPL 2020.10-rc3 (Sep 02 2020 - 12:24:07 -0500)
Trying to boot from UART
CC
*** file: u-boot.img
$ sx -vv u-boot.img
Sending u-boot.img, 6107 blocks: Give your local XMODEM receive command now.
Xmodem sectors/kbytes sent: 0/ 0kRetry 0: NAK on sector
Bytes Sent: 781824 BPS:7632
Transfer complete
*** exit status: 0 ***
xyzModem - CRC mode, 6109(SOH)/0(STX)/0(CAN) packets, 4 retries
Loaded 781724 bytes
U-Boot 2020.10-rc3 (Sep 02 2020 - 12:24:07 -0500)
CPU : AM335X-GP rev 2.1
Model: TI AM335x BeagleBone Black
DRAM: 512 MiB
WDT: Started with servicing (60s timeout)
NAND: 0 MiB
MMC: OMAP SD/MMC: 0, OMAP SD/MMC: 1
Loading Environment from FAT... <ethaddr> not set. Validating first E-fuse MAC
Net: eth2: ethernet@4a100000, eth3: usb_ether
Hit any key to stop autoboot: 0
=> version
U-Boot 2020.10-rc3 (Sep 02 2020 - 12:24:07 -0500)
arm-linux-gnueabihf-gcc (Linaro GCC 6.5-2018.12) 6.5.0
GNU ld (Linaro_Binutils-2018.12) 2.27.0.20161229
Regards,