Let's Make Robots!

Program freezed after Wire.endTransmission();

Has anyone ever seen this problem when using WIRE library? Recently I am trying MP3 player, RTC and other device with strange issue and it all points to when I use wire library the process halt right after the line "Wire.endTransmission();"

For example:

8x common anode RGB LED + resisters choices

Hi all,

I am planning to have 4 pair of common anode RGB LEDs and have each pair in Front-Left(FL), Front-Right(FR), Rear-Left(RL) and Real-Right(RR). Now, I am going to wire them up each pair so in the end to Arduino I will have R,G,B and common anode on each side.

Here is my question, where and which resister I should use? Should I connect both common anode in 5V or 3v3? Should I use resisters in each pin in RGB or common RGB after I connect them all together or common anode?

If you have better suggestion please let me know how to wire such setting up. Thanks a lot!

question about these numbers for "±3 / 11g" etc...

I saw one of those stores promote their new products and I always wondering what are those number stand for?

Such as: "±3 / 11g" Accelerometer or "±400° / s" Gyroscope..... What are those ± numbers and g or s means?

MP3 player shield from Sparkfun

Have anyone ever use this MP3 player? I got one of them and tried all 3 sample codes from their site with their sample MP3s but seems not working from my arduino. I am sure the SD card can be read cuz no error massege shows when i run the code.

Also search on the net but all I found are onlne stores or topics with no solutions. or any suggestions for other easy to use MP3 players?

TX2,RX2 on SPIDER board

I am using SPIDER for next project to run 30 servos plus XBEE with voice/sound control.

Never work with 2nd TX/RX port on Arduino before and not to sure if I do this correctly. I have search on web and see how it should be setup in any easy I could understand and following code is what I found and modified a bit to start of:

looking for two wheel driving formula with X, Y

I am using one joystick to control the robot. The range of value I fot from joy stick is 0~600 and the PWM to motor control is 40~140. So wheels will be nutrul around 95 as center point. 40 will go backward and 140 will go forward. This is what I have:

  int maxVal=140;
  int minVal=40;
  joyX = map(joyX, 0,600,minVal,maxVal);
  joyY = map(joyY, 0,600,minVal,maxVal);
  int speed_L = formula;
  int speed_R = formula;

Loosing power when read incoming serial signal from XBee

Have any of you seen the problem when you start getting signal from Xbee and lose the power?

this is the code I have:



void loop(){

  if(Serial.available() > 0) {





About wild thumper robot controller with XBee

Not sure if anyone done this before and I couldn't find anyone actually connect this controller with XBee. Does anyone know the proper way to connect XBee? D0 & D1 won't interfere with anything else?

Sending string via XBee and

I am sending string from Arduino to Arduino via Xbee. I don't know if this is the proper way to do it and I am open to know any feedbacks. Here is what I do, I am sending something from A and  it looks like:


Now, B is getting this string and trying to analyze it. Here is my code:


  if (Serial.available() > 0) {

    char incomingString = Serial.read();