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CyberMind-FR d1601fde8e docs(eye-remote): add U-Boot boot commands documentation

2026-04-23 11:32:07 +02:00

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ESPRESSObin U-Boot Boot Commands — Eye Remote

Overview

This guide covers configuring ESPRESSObin U-Boot to boot from Eye Remote mass storage (active slot) or TFTP (shadow slot). The Eye Remote Pi Zero W provides USB OTG connectivity and network access for dual-boot management.

Key network setup:

Eye Remote IP: 10.55.0.2
ESPRESSObin IP: 10.55.0.1
Network: 10.55.0.0/30 (routable via USB OTG ECM)

Prerequisites

Eye Remote Pi Zero W
- Running v2.1.0 or later
- USB OTG ECM mode enabled
- DHCP server active on 10.55.0.2
ESPRESSObin
- U-Boot installed in SPI NOR flash or eMMC
- Serial console access (TTL UART 115200 baud)
- USB OTG micro-AB port (supports OTG mode)
Connectivity
- USB OTG cable (Pi Zero ↔ ESPRESSObin USB OTG port)
- Serial console cable (UART3, pins TXD/RXD/GND)
- Optional: Ethernet for TFTP boot (fallback)
Host Files
- Kernel: Image (Linux ARM64 binary)
- DTB: armada-3720-espressobin.dtb (device tree)
- Present on Eye Remote mass storage or TFTP server

Power Ordering — Two Approaches

Option A: Independent Power (Recommended)

Safest method — power devices independently:

Connect USB OTG cable (Pi Zero ↔ ESPRESSObin OTG port)
- Pi Zero: micro-AB port
- ESPRESSObin: OTG micro-B port
- Cable acts as data link only
Power Pi Zero separately (5V via micro-USB)
- Pi Zero boots → enables USB host (via g_ether overlay)
- Exports mass storage LUN
Power ESPRESSObin independently (external 5V)
- Detects USB device (mass storage LUN) after U-Boot starts
- No risk of back-power or brown-out

Option B: Retry Loop in U-Boot

For scenarios where ESPRESSObin must power from USB OTG:

# In U-Boot console (press Enter during boot)
setenv bootcmd 'usb start; if usb storage; then fatload usb 0 ${kernel_addr_r} Image && fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb && booti ${kernel_addr_r} - ${fdt_addr_r}; fi; false'
saveenv
reset

U-Boot will:

Power on via USB OTG
Wait ~2s for Pi Zero to stabilize
Attempt usb start → usb storage
If USB device appears → load kernel/DTB → boot
If timeout → retry or fall back to TFTP

Mass Storage Boot (Active Slot)

Quick Check: USB Enumeration

Enter U-Boot console and verify USB device is detected:

ESPRESSObin=> usb start
Starting USB Controller
USB XHCI 1.00

ESPRESSObin=> usb storage
  Device 0: Vendor: QEMU     Rev: 2.5+ Type: Removable Hard Disk
            Capacity: 1024 MB = 1 GB (2097152 x 512)

ESPRESSObin=> usb tree
USB device tree:
  1  XHCI 1.00
     | 1 Hub: QEMU QEMU USB Storage Controller (product id 0x0070)
     | | 1 Mass Storage: QEMU USB Storage (000010000000000000000000)

Boot Command: Active Slot

Set boot command to load kernel and DTB from mass storage:

ESPRESSObin=> setenv bootcmd 'usb start; usb storage; fatload usb 0 ${kernel_addr_r} Image; fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb; booti ${kernel_addr_r} - ${fdt_addr_r}'

ESPRESSObin=> setenv bootargs 'root=/dev/mmcblk0p2 rw rootwait console=ttyMV0,115200'

ESPRESSObin=> saveenv
Saving Environment to SPI Flash... OK

Explanation:

usb start — Initialize USB controller
usb storage — Detect USB storage device
fatload usb 0 ${kernel_addr_r} Image — Load kernel from USB LUN 0
fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb — Load DTB
booti ${kernel_addr_r} - ${fdt_addr_r} — Boot with kernel at kernel_addr_r, no ramdisk, DTB at fdt_addr_r
saveenv — Persist to SPI NOR flash

Verify Boot Environment

List current environment variables:

ESPRESSObin=> printenv bootcmd
bootcmd=usb start; usb storage; fatload usb 0 ${kernel_addr_r} Image; fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb; booti ${kernel_addr_r} - ${fdt_addr_r}

ESPRESSObin=> printenv kernel_addr_r
kernel_addr_r=0x2000000

ESPRESSObin=> printenv fdt_addr_r
fdt_addr_r=0x1f00000

ESPRESSObin=> printenv bootargs
bootargs=root=/dev/mmcblk0p2 rw rootwait console=ttyMV0,115200

TFTP Boot (Shadow Slot)

Prerequisite: TFTP Server

Set up TFTP on Eye Remote or a separate machine:

# Eye Remote (10.55.0.2) or host on 10.55.0.0/30 network
mkdir -p /srv/tftp
cp Image /srv/tftp/
cp armada-3720-espressobin.dtb /srv/tftp/

# Start dnsmasq or in.tftpd listening on 10.55.0.2:69
systemctl restart dnsmasq
# or
systemctl restart tftpd-hpa

Boot Command: Shadow Slot

Configure TFTP boot for failover scenarios:

ESPRESSObin=> setenv serverip 10.55.0.2

ESPRESSObin=> setenv bootcmd 'usb start; if usb storage; then fatload usb 0 ${kernel_addr_r} Image && fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb && booti ${kernel_addr_r} - ${fdt_addr_r}; else tftp ${kernel_addr_r} Image && tftp ${fdt_addr_r} armada-3720-espressobin.dtb && booti ${kernel_addr_r} - ${fdt_addr_r}; fi'

ESPRESSObin=> saveenv

Logic:

Try USB mass storage boot (active slot)
If USB fails or times out → TFTP boot (shadow slot)
Either way, boot the kernel + DTB combination

Direct TFTP Boot (No Fallback)

For testing the TFTP shadow channel in isolation:

ESPRESSObin=> setenv serverip 10.55.0.2

ESPRESSObin=> tftp ${kernel_addr_r} Image
Using usb_ether device
TFTP from server 10.55.0.2; our IP address is 10.55.0.1
Filename 'Image'.
Load address: 0x2000000
Loading: #################################################################
         1234 Bytes/s
done
Bytes transferred = 16384000 (fa80000 in hex)

ESPRESSObin=> tftp ${fdt_addr_r} armada-3720-espressobin.dtb
Using usb_ether device
TFTP from server 10.55.0.2; our IP address is 10.55.0.1
Filename 'armada-3720-espressobin.dtb'.
Load address: 0x1f00000
Loading: #
done
Bytes transferred = 32768 (8000 in hex)

ESPRESSObin=> booti ${kernel_addr_r} - ${fdt_addr_r}

Workflow: Test Then Promote

Phase 1: Upload to TFTP (Shadow)

Build new kernel and DTB on development machine

Copy to TFTP server at /srv/tftp/

scp Image root@10.55.0.2:/srv/tftp/
scp armada-3720-espressobin.dtb root@10.55.0.2:/srv/tftp/

Phase 2: Test via TFTP (Shadow Boot)

Interrupt U-Boot at prompt
Clear USB first (in case old device present):
```
ESPRESSObin=> usb reset
```

Boot via TFTP:

ESPRESSObin=> setenv serverip 10.55.0.2
ESPRESSObin=> tftp ${kernel_addr_r} Image
ESPRESSObin=> tftp ${fdt_addr_r} armada-3720-espressobin.dtb
ESPRESSObin=> booti ${kernel_addr_r} - ${fdt_addr_r}

Phase 3: Verify Boot Success

Once kernel boots, verify via SSH:

ssh root@10.55.0.1
# Verify kernel version, modules, etc.
uname -a

Phase 4: Promote to Active Slot (USB Mass Storage)

Once TFTP boot is verified:

Copy files to Eye Remote mass storage

scp Image root@10.55.0.2:/mnt/usb/boot/
scp armada-3720-espressobin.dtb root@10.55.0.2:/mnt/usb/boot/

Update U-Boot bootcmd to use USB:

ESPRESSObin=> setenv bootcmd 'usb start; usb storage; fatload usb 0 ${kernel_addr_r} Image; fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb; booti ${kernel_addr_r} - ${fdt_addr_r}'
ESPRESSObin=> saveenv

Reset and verify USB boot:
```
ESPRESSObin=> reset
```

Troubleshooting

Issue: "No USB storage device(s) found"

Cause: Pi Zero not detected or not in host mode.

Diagnosis:

ESPRESSObin=> usb start
Starting USB Controller
USB XHCI 1.00

ESPRESSObin=> usb tree
USB device tree:
  1  XHCI 1.00
     1 Hub: QEMU QEMU USB Storage Controller (product id 0x0070)
     (nothing under hub — no device)

Solutions:

Check Pi Zero power: Verify 5V applied to Pi Zero micro-USB port

# On Pi Zero:
vcgencmd get_throttled  # Should be 0x0 (no throttle)

Check USB cable: Swap cable, verify all connections

# On Pi Zero:
lsusb
# Should show usb_ethernet module loaded
lsmod | grep g_ether

Restart U-Boot retry loop: Reset both devices
```
ESPRESSObin=> reset
```
Check Eye Remote ECM driver: On Pi Zero, verify interface is up
```
ip link show usb0
# Should be "UP"
```

Issue: "Unable to read file Image"

Cause: File not found on mass storage, or incorrect filename.

Diagnosis:

ESPRESSObin=> usb storage
ESPRESSObin=> fatls usb 0
(no files listed, or different names)

Solutions:

Verify file exists on Eye Remote:
```
ls -lh /mnt/usb/boot/Image
```

Check FAT filesystem:

mount | grep usb0
fsck.vfat -v /dev/sda1

Verify filename case: U-Boot FAT driver is case-sensitive

ESPRESSObin=> fatls usb 0
# Should show "Image" (capital I)

Recreate boot partition if corrupted:

mkfs.vfat -F 32 /dev/sda1
mkdir -p /mnt/usb/boot
mount /dev/sda1 /mnt/usb/boot
cp Image armada-3720-espressobin.dtb /mnt/usb/boot/
umount /mnt/usb/boot

Issue: TFTP Timeout

Cause: Network unreachable, TFTP server down, or firewall blocking.

Diagnosis:

ESPRESSObin=> setenv serverip 10.55.0.2
ESPRESSObin=> tftp ${kernel_addr_r} Image
Using usb_ether device
TFTP from server 10.55.0.2; our IP address is 10.55.0.1
Filename 'Image'.
Load address: 0x2000000
Waiting for ethernet device... timeout!

Solutions:

Verify network connectivity:

# On Pi Zero or test host
ping 10.55.0.1
# Should succeed

Check TFTP server is running:

systemctl status dnsmasq  # or tftpd-hpa
netstat -uln | grep :69   # TFTP port

Verify firewall allows TFTP:

ufw allow 69/udp
# or nftables
nft add rule inet filter input udp dport 69 accept

Test TFTP connectivity manually:

# On test host on 10.55.0.0/30 network
echo "test" > /srv/tftp/test.txt
tftp 10.55.0.2
> get test.txt

Set TFTP timeout in U-Boot:

ESPRESSObin=> setenv netretry 5
ESPRESSObin=> saveenv

Issue: Kernel Loads but Won't Boot

Symptoms: Files load successfully, but kernel crashes or hangs.

Diagnosis:

ESPRESSObin=> booti ${kernel_addr_r} - ${fdt_addr_r}
## Flattened Device Tree blob at 1f00000
## Kernel loaded from 0x02000000
## Loading Device Tree to 27f00000, end 27f08000 ... OK
## Booting using the fdt blob at 0x27f00000
(hangs here)

Solutions:

Verify DTB matches kernel version:

file armada-3720-espressobin.dtb
# Should show "Device Tree Blob"

Check kernel bootargs:

ESPRESSObin=> printenv bootargs
# Verify root= device exists

Enable serial console on kernel side:

ESPRESSObin=> setenv bootargs 'root=/dev/mmcblk0p2 rw rootwait console=ttyMV0,115200 earlyprintk'
ESPRESSObin=> saveenv

Rebuild kernel with proper config:

# Ensure CONFIG_SERIAL_MVEBU_UART=y in kernel .config
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
     mvebu_v7_defconfig

Environment Variable Reference

Variable	Default	Purpose
`bootcmd`	varies	Command executed at boot
`bootargs`	varies	Kernel boot arguments (root, console, etc.)
`kernel_addr_r`	0x2000000	DRAM address for kernel load
`fdt_addr_r`	0x1f00000	DRAM address for DTB load
`ramdisk_addr_r`	varies	DRAM address for ramdisk (if used)
`serverip`	10.55.0.2	TFTP server IP
`ipaddr`	10.55.0.1	ESPRESSObin IP (USB OTG)
`netmask`	255.255.255.252	Network mask for USB OTG link
`netretry`	1	TFTP retry count

To view all:

ESPRESSObin=> printenv

To save any change:

ESPRESSObin=> saveenv

Examples

Full Bootcmd with Fallback

Active slot (USB) with fallback to shadow slot (TFTP):

setenv bootcmd 'usb start; if usb storage; then echo "Booting from USB..."; fatload usb 0 ${kernel_addr_r} Image && fatload usb 0 ${fdt_addr_r} armada-3720-espressobin.dtb && booti ${kernel_addr_r} - ${fdt_addr_r}; else echo "USB boot failed, trying TFTP..."; tftp ${kernel_addr_r} Image && tftp ${fdt_addr_r} armada-3720-espressobin.dtb && booti ${kernel_addr_r} - ${fdt_addr_r}; fi'

setenv bootargs 'root=/dev/mmcblk0p2 rw rootwait console=ttyMV0,115200'

saveenv
reset

Development Iteration (TFTP Only)

For rapid kernel development, stay on TFTP:

setenv bootcmd 'usb reset; setenv serverip 10.55.0.2; tftp ${kernel_addr_r} Image && tftp ${fdt_addr_r} armada-3720-espressobin.dtb && booti ${kernel_addr_r} - ${fdt_addr_r}'

setenv bootargs 'root=/dev/mmcblk0p2 rw rootwait console=ttyMV0,115200 earlyprintk'

saveenv
reset

Author: CyberMind — Gérald Kerma License: Proprietary / ANSSI CSPN candidate Last Updated: 2024

13 KiB Raw Blame History

ESPRESSObin U-Boot Boot Commands — Eye Remote

Overview

Prerequisites

Power Ordering — Two Approaches

Option A: Independent Power (Recommended)

Option B: Retry Loop in U-Boot

Mass Storage Boot (Active Slot)

Quick Check: USB Enumeration

Boot Command: Active Slot

Verify Boot Environment

TFTP Boot (Shadow Slot)

Prerequisite: TFTP Server

Boot Command: Shadow Slot

Direct TFTP Boot (No Fallback)

Workflow: Test Then Promote

Phase 1: Upload to TFTP (Shadow)

Phase 2: Test via TFTP (Shadow Boot)

Phase 3: Verify Boot Success

Phase 4: Promote to Active Slot (USB Mass Storage)

Troubleshooting

Issue: "No USB storage device(s) found"

Issue: "Unable to read file Image"

Issue: TFTP Timeout

Issue: Kernel Loads but Won't Boot

Environment Variable Reference

See Also

Examples

Full Bootcmd with Fallback

Development Iteration (TFTP Only)

13 KiB

Raw Blame History