user@UbuntuLTS2:~$ picocom -b 115200 /dev/ttyUSB0
picocom v2.2

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
nolock is      : no
send_cmd is    : sz -vv
receive_cmd is : rz -vv -E
imap is        : 
omap is        : 
emap is        : crcrlf,delbs,

Type [C-a] [C-h] to see available commands

Terminal ready

U-Boot SPL 2019.01-g350f3927b8 (Feb 17 2020 - 09:46:23 +0000)
SYSFW ABI: 2.9 (firmware rev 0x0013 '19.12.1-v2019.12a (Terrific Lla')
Trying to boot from SPI
Loading Environment from MMC... spl: unsupported mmc boot device.
sdhci@4f80000 - probe failed: -19
spl: unsupported mmc boot device.
sdhci@4fb0000 - probe failed: -19
*** Warning - No MMC card found, using default environment

Loading rproc fw image from device 3 not supported!
Loading rproc fw image from device 3 not supported!
Starting ATF on ARM64 core...

NOTICE:  BL31: v2.2(release):ti2019.05-rc1
NOTICE:  BL31: Built : 09:32:00, Feb 17 2020
I/TC: 
I/TC: OP-TEE version: ti2019.05-rc1-dev (gcc version 8.3.0 (GNU Toolchain for the A-profile Architecture 8.3-2019.03 (arm-rel-8.36))) #1 Mon Feb 17 09:40:16 UTC 2020 aarch64
I/TC: Initialized

U-Boot SPL 2019.01-g350f3927b8 (Feb 17 2020 - 09:48:06 +0000)
Detected: J7X-BASE-CPB rev E3
Detected: J7X-VSC8514-ETH rev E2
Trying to boot from SPI


U-Boot 2019.01-g350f3927b8 (Feb 17 2020 - 09:48:06 +0000)

SoC:   J721E PG 1.0
Model: Texas Instruments K3 J721E SoC
Board: J721EX-PM2-SOM rev E7
DRAM:  4 GiB
Flash: 0 Bytes
MMC:   sdhci@4fb0000 - probe failed: -123
sdhci@4f80000: 0
Loading Environment from MMC... OK
In:    serial@2800000
Out:   serial@2800000
Err:   serial@2800000
Detected: J7X-BASE-CPB rev E3
Detected: J7X-VSC8514-ETH rev E2
Net:   
Warning: ethernet@046000000 using MAC address from ROM
eth0: ethernet@046000000
Hit any key to stop autoboot:  0 
no mmc device at slot 1
SD/MMC found on device 1