Widemac SL-R720X / XDX-RN502J

This device is NOT RECOMMENDED for future use with OpenWrt due to low flash/ram.
DO NOT BUY DEVICES WITH 4MB FLASH / 32MB RAM if you intend to flash an up-to-date and secure OpenWrt version onto it! See 4/32 warning for details.

1) This device does not have sufficient resources (flash and/or RAM) to provide secure and reliable operation.
This means that even setting a password or changing simple network settings might not be possible any more, rendering the device effectively useless. See OpenWrt on 4/32 devices what you can do now.

2) OpenWrt support for this device has ended in 2022.
19.07.10 was the last official build for 4/32 devices.

This is a white-label mass-market ralink-based router produced by Bococom, selling under the Widemac SL-R720X label. The device is sometimes also referred to as XDX-RN502J, a string that appears prominently on the PCB board. Some of the devices ship with OpenWrt preinstalled.

Please check out the article flash.layout. It contains an example and a couple of explanations.

On this device, flash layout is the following:

0x000000000000-0x000000030000 “u-boot”
0x000000030000-0x000000040000 “u-boot-env”
0x000000040000-0x000000050000 “factory”
0x000000050000-0x000000150000 “kernel”
0x000000150000-0x000000400000 “rootfs”

auto-created partitions at boot:

  • mtd: partition “rootfs” set to be root filesystem
  • mtd: partition “rootfs_data” created automatically, ofs=2E0000, len=120000
0x0000002e0000-0x000000400000 “rootfs_data”
0x000000050000-0x000000400000 “firmware”

OpenWrt was installed with the serial port and tftp method. There is currently no known way to flash directly from the built-in firmware. So, follow generic.flashing.tftp for general setup of a tftp server and firmware to load. Use the sysupgrade image. Set your terminal to 57600 bauds, 8,N, 1. At boot, you will see the following on your serial terminal:

please choose the operation: 1: Load system code to SDRAM via TFTP. 2: Load system code then write to Flash via TFTP. 3: Boot system code via Flash (default). 4: Entr boot command line interface. 9: Load Boot Loader code then write to Flash via TFTP.

choose 2, then answer the prompts. Note that option 1 does not work with the sysupgrade image; booting will fail on finding the root partition.

After installation, copy-paste the following configuration into /etc/config/network

config interface 'loopback'
      option ifname 'lo'
      option proto 'static'
      option ipaddr ''
      option netmask ''

config globals 'globals'
      option ula_prefix 'fd37:bd9a:2b09::/48'

config switch 'switch0'
      option enable '1'
      option enable_vlan '1'
      option reset '1'

config switch_vlan
      option vlan '1'
      option device 'switch0'
      option ports '0 6t'

config switch_vlan
      option vlan '2'
      option device 'switch0'
      option ports '1 2 3 4 6t'

config switch_port                                         
      option port '0'
      option pvid '1'

config interface 'lan'
      option force_link '1'
      option type 'bridge'
      option proto 'static'
      option ipaddr ''
      option netmask ''
      option ip6assign '60'
      option _orig_ifname 'eth0.2 wlan0'
      option _orig_bridge 'true'
      option ifname 'eth0.2'
      option nat '1'

config interface 'wan'
      option proto 'dhcp'
      option _orig_ifname 'eth0.1'
      option _orig_bridge 'false'
      option ifname 'eth0.1'
      option broadcast '1'

Reboot, and the network ports should be operational.

WARNING: The current OpenWrt image does not contain a valid configuration for the various wired network ports
on the device. As a result, wired networking broken until copy-pasting in the above configuration.


If you have already installed OpenWrt and like to reflash for e.g. upgrading to a new OpenWrt version you can upgrade using the mtd command line tool. It is important that you put the firmware image into the ramdisk (/tmp) before you start flashing.

LuCI Web Upgrade Process

Terminal Upgrade Process

  • Login as root via SSH on
  • Use the following commands to upgrade.
cd /tmp/
wget http://downloads.openwrt.org/snapshots/trunk/XXX/xxx.abc
sysupgrade /tmp/xxx.abc
  • If sysupgrade does not support this router, use the following commands.
cd /tmp/
wget http://downloads.openwrt.org/snapshots/trunk/XXX/xxx.abc
mtd write /tmp/xxx.abc linux && reboot

Basic configuration After flashing, proceed with this.
Set up your Internet connection, configure wireless, configure USB port, etc.

hardware.button on howto use and configure the hardware button(s).

The SL-R720X devices has one button. In the original configuration it resets the router when pressed for 5 seconds and switches WPS mode when pressed for only 1 second.

1 sec WPS
5 sec reset

The default network configuration is:

Interface Name Description Default configuration
br-lan LAN & WiFi
vlan0 (eth0.1) LAN ports (1 to 4) None
vlan1 (eth0.2) WAN port DHCP
wl0 WiFi Disabled

Numbers 1-4 are ports 1-4 as labeled on the unit, number 0 is the Internet (WAN) on the unit, 6 is the internal connection to the router itself. vlan0 = eth0.0, vlan1 = eth0.1 and so on.

Port Switch port
0 Internet (WAN)
1 LAN 1
2 LAN 2
3 LAN 3
4 LAN 4
5 non-connected?
6 CPU (internal)
Architecture MIPS
Vendor Ralink
bootloader U-Boot
System-On-Chip RT3052
CPU/Speed 24Kc 384 MHz
Flash-Chip 29LV320DBTI-70G/ST 25P64V6P
Flash size 4096 KiB
RAM 32 MiB
Wireless rt2872 2.4GHz 802.11bgn
Ethernet ?
USB Yes 1 x 2.0
GPIO Yes 6 free
Serial Yes

Model Number / Backside label
Insert picture

Case Front:
Insert picture

Case Back:
Insert picture

Note: This will void your warranty!

  • To remove the cover just unscrew the four corner phillips screws under the rubber feet.


PCB bottom

The serial port is on the unpopulated header labelled “console”/“J2”. Pins are, from the pin closest to J2 Gnd, Rx, Tx, Vcc. Use a 5V ↔ 3.3V level shifter. Some of the boards are shipped with a populated header. Use 57600 8N1, hard & soft flow control OFF.

Insert photo of PCB with markings

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  • Last modified: 2024/02/12 08:58
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