Saturday, July 23, 2011


My first prototype of a four-legged robot.
12 servo motors controlled by STM32F103RB (MiniSTM32 board).

It was previously a "tripod" =) . But then, later, another leg was added (3 servos per leg) for easy balancing even without using IMU sensors.

         * PhilRobotics @ MOA July 17, 2011 (pics by vic)

Sunday, April 3, 2011

WM8505 LCD driver

Another low-level hack on my Android Apad ( clone/fake Apad? ).

This time it's now with the 800x480 GLCD driver. It's working, but I'm not sure if the initialization is complete (i.e. the hardware is, most probably, already initialized by the bootloader). I've just modified the sources from Wondermedia (look at "\common\wmt_logo\" folder). LCD routines here are not using the graphics engine (GE) of WM8505.

download Eclipse project here:

Read my previous post on how to set-up the tool-chain and how to load the program on WM8505.

    expected output:

forum link: Re: Let's learn ARM using cheap 7" tablets

Tuesday, March 29, 2011

Hello World, WM8505!

 My first step in learning the ARM9 platform.

VIA / WonderMedia's WM8505 (ARM926EJ-S):

UART0 Connection:

Serial console connection details:  Project Gus

Required Tools:  all are free =) 

The goal is to run this simple code: (main.c)

 It should output these strings on UART_0 port, just like this:

 After setting up the tools, here are the next steps:
-Create new project on Eclipse

 -Select target processor (WM8505 is a ARM926EJ-S processor)

-Select binary format for the flash image:

-linker setting:

 - after building the project, open the generated *.map file to verify the linker output
    *I don't know, yet, what's with this 0x03F80000 address.
      This is the load address used by Wondermedia version of U-BOOT

- Complete Eclipse project files:
download here:

* most of the hardware initializations (e.g. clock settings) are already done by the bootloader,
   so we don't have to worry about them for now.

Next question is, "how to load and run the code?
I've tested two ways of how to transfer the generated image to the RAM:
First is through tftp transfer, second is SD card load during boot-up.
Both method uses the bootloader, which is already present in the board (in the SPI flash).
My board got v1.1.4 of U-BOOT.

1. TFTP transfer to RAM.
- get a copy of this freeTFTPD32 server application.
- using the LAN adapter, connect board to host PC Ethernet
enter u-boot console, and type these commands:

* RAM load address can use other than 0x0

2. SD card scriptcmd
-guide:  How to edit "scriptcmd"
-during boot-up, the u-boot will read the "scriptcmd" script in the "script" folder of the SD card.

*these commands can also be typed in the uboot console. ("mmcinit" must be sent first)

Wondermedia GPL sources
WM8505 datasheets
forum link:
Let's learn ARM using cheap 7" tablets

Thursday, February 3, 2011

MARG sensors + Bluetooth

MARG (Magnetic, Angular Rate, and Gravity) sensor array used for AHRS (Attitude and Heading Reference Systems).

Android OpenGL 3D display on Samsung Spica (i5700).

Sparkfun 9DOF sensor stick SEN-10389, later replaced by SEN-10321.

Using ATmega328P, operated at 3.3V supply and 8MHz crystal. At this speed, reading sensors' measurements and computing "AHRSupdate" take about 31ms to complete. Default compiler setting is used on WinAVR. With 25Hz sampling rate, this leaves mega328p extra 9ms to do other tasks. Bluetooth SPP (serial) communication is buffered and interrupt driven, so no processing time is wasted in reading and sending data to the android phone.

(1) Sebastian Madgwick's Alternative AHRS (MARG) algorithm - Quaternion implementation of Mayhony's DCM filter incorporating magnetic distortion compensation.
(2) Fabio Varesano's FreeIMU. Also using Madgwick's implementation of the DCM filter on Arduino platform.
(3) Rotation convertions by Martin Baker. Very good discussion on quaternions and other 3D representation like Euler angles and transformation matrix.
(4) OpenGL Transformation Matrix by Song Ho Ahn
(5) Similar discusion on started by Harinath

Android project examples:
Android Bluetooth
Bluetooth Chat
Android OpenGL Projects
OpenGL ES tutorial
Android Bluetooth Oscilloscope

Special thanks to the generous guy who gave me these toys, Thank you very much!

Wednesday, January 19, 2011