AN809 Datasheet, PDF (8/10 Pages) Silicon Laboratories – VIRTUAL COM PORT DRIVER INTO THE ANDROID PLATFORM

AN809
At this point everything is setup to build the CP210x in to the kernel.
Note: The Android Jelly Bean (4.3.1) OS is based on a 2.6 version of the Linux kernel. Basic support for CP2101/2/3 devices
are included in the kernel by default, but the driver is not up to date for newer devices such as CP2104/5/8/9. To get sup-
port for these, you will need to replace the cp210x.c driver file in the source before you build your kernel image. Perform
the following steps to replace the file:
1. Download the Linux 2.6 driver from the Silicon Labs website:
http://www.silabs.com/Support%20Documents/Software/Linux_2.6.x_VCP_Driver_Source.zip
2. Extract the cp210x.c file in to the kernel source tree. The original cp210x.c file is located in the tree under <base kernel
directory>/drivers/usb/serial.
3. Rebuild the kernel using the steps below.
8. Build and Install the New Image
Once you confirm your device works and boots off of the known media, you have downloaded the necessary
toolchain and the Android kernel source tree can build your kernel image.
1. To build the source run the following command:
$ make ARCH=arm CROSS_COMPILE=arm-linux=andorideabi- uImage
2. When your build completes successfully, you can find your ‘uImage’ file under <base kernel directory>/
arch/arm/boot.
3. The final step is to replace the “uImage” file on the boot device with the new one. Reinsert the original SD
card that contains the prebuilt bootable image. You should see multiple partitions come up on this device.
Navigate to the “boot” partition and delete the “uImage” file on the device, then copy over the new one from
your build.
4. The SD card is now ready to boot. Insert it into the SD card slot on the PandaBoard, hook up a monitor to
the HDMI output and a keyboard and mouse to the USB ports. Connect the RS232 connection up to your
development system using minicom or some other terminal program (115200, 8N1).
9. Testing the CP210x Driver in Android
When your PandaBoard boots up, you can plug in a CP210x device to the USB host port on the PandaBoard. On
the host terminal connected to the Android debug port you should see something similar to the following output:
[ 104.627380] usb 1-1.3: new full-speed USB device number 8 using ehci-
omap
[ 104.764923] usb 1-1.3: New USB device found, idVendor=10c4,
idProduct=ea60
[ 104.772338] usb 1-1.3: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[ 104.786437] usb 1-1.3: Product: CP2104 USB to UART Bridge Controller
[ 104.803405] usb 1-1.3: Manufacturer: Silicon Labs
[ 104.810241] usb 1-1.3: SerialNumber: 0001
[ 104.836822] cp210x 1-1.3:1.0: cp210x converter detected
[ 104.845794] usb 1-1.3: cp210x converter now attached to ttyUSB0
The last line will specify what tty device the CP210x will be accessible through, in this case it is “ttyUSB0”.
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