Tuesday, September 7, 2010

Reboot-Persisting All-User-Access USB Serial Port on Froyo

I turned the USB into a serial port. Then, I noticed it wasn't usable without superuser permissions. Recently, I got some great information from a former Android coder and have now have a permanent fix that persists on reboot with Android 2.2 (Froyo).

First, I edit init.mahimahi.c
(mahimahi is the board for Nexus One (aka HTC Passion), if you're working on another HTC device, you'll need to edit the right file for your device).
$ gedit path/to/device/htc/passion/init.mahimahi.c

I put the following at lines 64 and 65.
#mwk: Enable Serial Port for all users
chmod 0777 /dev/ttyMSM0

I run lunch.
~/mydroid$ . build/envsetup.sh
~/mydroid$ lunch
I choose option 4 (full_passion)

I plug in a Nexus One and extract the device info.
~/mydroid$ cd device/htc/passion
~/mydroid/device/htc/passion$ ./extract-files.sh

I re-make the AOSP.
~/mydroid/device/htc/passion$ cd ../../..
~/mydroid$ make

I get the phone in bootloader mode (the fast way).
$ adb reboot-bootloader

I flash the device. (On this website, step 14 didn't work for me, so I now run the command this way.)
~/mydroid/out/host/linux-x86/bin$ sudo ./fastboot -p passion -w flashall

On the phone, I enable applications from unknown sources.
Settings--> Applications --> Unknown sources --> checked

Also, on the phone, I enable USB Debugging, Stay Awake, and Allow Mock Locations.
Settings--> Applications --> Development --> checked all three


  1. So what are you planning to make with all this serial port hacking?

  2. Right now, we have an apk to ask phone health information and we receive that data via the serial port.

  3. Please, I have Samsung Galaxy S4 and I need read USB serial port (OTG). Can you help me please. I don´t know how to do it.