delx.au / blog

I bought the Acer Iconia A501 on special from Telstra for $200 a while back. It’s a good tablet and that was a great price for it, however I’ve been annoyed that Telstra hasn’t bothered to release the Android 4.0 Ice Cream Sandwich update that Acer released for unbranded devices. Acer blames Telstra for not releasing it and Telstra blames Acer for not making it available. Bleh.

Fortunately it was not too hard to unbrand the device and upgrade all the way to Android 4.0.3 and presumably 4.1 when Acer finishes that update too.

Requirements

• Acer Iconia Tablet A501 (may work with other models but I haven’t tried)
• PC to download the updates
• MicroSD card to transfer the updates to the tablet

Obtaining the Update File

The update files come named like Acer_A501_1.2.3_9.9.9_EMEA_CUS7_1313721527367_dc802d69.zip. This update would be a patch for the A501 model for the EMEA region, running version 1.2.3. It would bring you up to version 9.9.9. Most Acer updates seem to be distributed as patches like this. It decreases the download size necessary but means that you cannot just install one of these updates on your tablet unless you were running the exact version and region for which the patch was written. Also it’s worth noting that version 4.0 of the Acer firmware is actually Android 3.2, these version numbers do not correlate at all.

Fortunately Acer does have full version downloads of Android 3.2 available! I got them using curl on my Linux PC. First you’ll need to download checkin.txt. This lets us pretend to be running an old enough version that Acer gives us the full update instead of a patch. The magic file is bolded below:

$ curl -i -H "Content-Type: application/json" -X POST -d "@checkin.txt" http://checkin.acer.futuredial.com/fotacheckin/rest/checkin
HTTP/1.1 200 OK
Date: Thu, 08 Nov 2012 10:02:36 GMT
Transfer-Encoding: chunked
Accept-Ranges: bytes
Server: Noelios-Restlet-Engine/1.1.6
Content-Length: 1004
Content-Type: application/json; charset=UTF-8
X-Powered-By: Servlet/2.5 JSP/2.1

{"logging_id":"0000000000000000000000000000000000000000", "time_msec":"1352368956277", "stats_ok":true, "group":"public", "rule_id":"1725", "package_format":"DOUBLE", "topic":null, "digest":"9ba31cba5bcd3d7d6a37c5e401be64d", "intent":[{"extra":[{"name":"promptMessage", "value":"-"}, {"name":"promptFeature", "value":"-"}, {"name":"promptVersion", "value":"acer_a501_4.031.04_emea_cus7"}, {"name":"promptSize", "value":"355.34 MB"}, {"name":"promptMinutes", "value":"30,..."}, {"name":"timeoutSeconds", "value":"120"}, {"name":"rawsize", "value":"null"}, {"name":"zipsize", "value":"null"}, {"name":"mcc_mnc_profile", "value":"1"}, {"name":"mcc_mnc_limit", "value":"0"}], "action":"android.server.checkin.FOTA_UPDATE", "data_uri":"http://cdn.a1.futuredial.com/Acer_A501_0.000.00_4.031.04_EMEA_CUS7_1315980517522_24980aa3.zip"}], "setting":[{"name":"upload_crash", "value":"http://122.248.251.200/crash block"}, {"name":"checkin_interval", "value":"43200"}, {"name":"upload_event", "value":"false"}, {"name":"update_stats","value":"false"}]}


‘Decrypting’ the Update File

You’ll find that you cannot open it as Acer obfuscates these files by XORing each byte with 0x12. I’ve written xor.c to fix this.

$ gcc -Wall -Wextra -std=c99 -o xor xor.c
$ ./xor Acer_A501_0.000.00_4.031.04_EMEA_CUS7_1315980517522_24980aa3.zip Acer_A501_0.000.00_4.031.04_EMEA_CUS7_1315980517522_24980aa3_decrypted.zip
$ unzip Acer_A501_0.000.00_4.031.04_EMEA_CUS7_1315980517522_24980aa3_decrypted.zip


Copy the update.zip you got from the previous step onto your MicroSD card and put it into your table. Next shut down the tablet. Now when you turn it back on hold the volume down key (side closest to the power button) at the same time as the power button. The tablet should start installing the update. Once this is done you should be able to use the builtin updater to go all the way to ICS.

Manually Downloading the ICS Update

If you so wish it’s easy to repeat the previous steps so you get multiple update.zip files. Simply modify the firmware_version field in checkin.txt and run through the steps again. Here were the successive versions I used and the update files I obtained:

• Acer_A501_4.017.03_EMEA_CUS7 -> Acer_A501_0.000.00_4.031.04_EMEA_CUS7_1315980517522_24980aa3.zip
• Acer_A501_4.031.04_EMEA_CUS7 -> Acer_A501_4.031.04_4.066.04_EMEA_CUS7_1324005431750_cadedfb2.zip
• Acer_A501_4.066.04_EMEA_CUS7 -> Acer_A501_4.066.04_4.066.05_EMEA_CUS7_1324005364360_cd119914.zip
• Acer_A501_4.066.05_EMEA_CUS7 -> Acer_A501_4.066.05_041.220.05_EMEA_CUS7_1343276448238_2c529a7e.zip

That last version 041.220.05 strangely enough is Android 4.0.3 ICS.

Now lets hope Acer releases Android 4.1 sometime soon! :)