Isl3893-Y.A.R.C - Yet another ReCovery-HOWTO

Recovering an isl3893-AP after a bad firmware-flash

You can recover either using Safe Mode or a recovery image

Method 1: Safe Mode

Turn AP off, press the reset-button, keep it pressed and switch back on. The AP will then respond to IP 192.0.2.93, TFTP and ping only. You can then upload a firmware image. (Set you PCs IP accordingly, of course :-)

On windows:
tftp -i 192.0.2.93 PUT <name of firmware imagefile>

On linux:
tftp 192.0.2.93
verbose
trace
binary
put <name of firmware imagefile>
quit

Uploading this way takes 1-2 minutes, the LAN-LED flashes very fast during that time. Then the AP should automatically reboot. It may then take another 2-3 minutes before the AP responds again.

It helps to have a sniffer listening to the LAN-interface of the PC. You can immediately see if TFTP is uploading the firmware, and later when the AP is back online you may be able to see broadcasts, DHCP-discovery packets or other network-traffic to/from the AP. Usually you can see the current IP of the AP, in case you are unsure.

You may get the error-message "firmware image exceeds flash-size". In that case see section Recovery Image

Method 2: Recovery Image

The error-message "firmware image exceeds flash-size" means the the previously flashed firmware has repartitioned the flash-memory of the AP. The partition for the firmware can then be too small for any other image, often even including the one that reset the partitions.

IMHO the bootloader is designed very badly. It should be able to reset the partitions if necessary before or during firmware-upload.

The publicly available firmware-sources usually have pre-set partition-sizes 10000/1b0000/200000. The can be changed before compiling the sources, see make menuconfig. Try for example 10000/200000/360000. That helps avoid the "exceeds flash-size"-error.

Recovery-Upload

For recovery get a small firmware-image like apfw.minimal.img

You will also need imginstall

apfw.minimal.img usually fits even if the partitions are misconfigured. Upload it as described in section Safe Mode Then set your PC to an IP fitting the default-IP of apfw.minimal.img, 192.168.24.23

After upload, reboot and another 2 minutes (use sniffer to monitor) you should be able to telnet 192.168.24.23. FTP should also work.

Flashing new Firmware

Then FTP 192.168.24.23
cd /var
binary
put imginstall
put <another firmware image-file.img>
quit

Then telnet 192.168.24.23
cd /var
chmod +x imginstall
/var/imginstall -k /var/ <firmware image-file.img>

You should get a message like "programming block N" every few seconds. After about 25 programmed blocks the message "rebooting in 5 seconds" should come up.

Then wait while the AP reboots, and set the IP of your PC to fit the default IP of the newly flashed image, usually 192.168.1.254, 192.168.0.1 or a few others, depending on the manufacturer of the newly flashed firmware. If you do not know the IP try the sniffer or google for the default IP of the manufacturer.

The AP should then behave according the features of the firmware.

Other Links

See Ruben's page: http://www.student.kuleuven.ac.be/~s0169612/isl3893.html

• section "Flashing large firmware images"
• section "Recovering the AP from a bad firmware image"