Let's Make Robots!


pins specification

i need to know the pin configurations of usb,serial,and parallel ports of a computer.....someone make me understand about the micro processor DDR,registor,address,etc evrythig related to a micro processor..

Problem with Ultrasound Sensor

Hello LMR.

I am working on a current project but seem to be having a ridiculous amount of difficulty implementing an SRF02 Ultrasound sensor. I am using it in serial mode and communicating with an Arduino Duemilanove. The problem is not in the wiring as I triple checked that.

The adruino is supposed to send 2 bytes to the SRF02 [ address, command ] and then receive 2 bytes in response giving the distance measured by the sensor.

Tracks human faces using a webcamera and two servo motors to pan and tilt
Using a
This is my first time using OpenCV, an open source computer vision library developed by Intel Corporation.  It wasn't too hard to get setup or use OpenCV in … Read more

ISP or Serial programming an Arduino

I am the proud owner of an uBotino board by Robot-x. I do not own a USB-to-Arduino cable (FTDI with auto-reset). However, I do own computers with good old fashioned serial ports.

So I think I'm gonna build a serial programming circuit. Would the classic "Picaxe" level-correcting schematic work in this case?

* a voltage divider to shift down the signal from my PC from ca 11V to 5V;
* a series resistor in both data lines to limit current;

Serial RFID reader troubles

I recently purchased the seeedstudio serial RFID reader for 125khz tags, but I cant really understand the datasheet. I am having trouble figuring out how I am supposed to interface it with my picaxe. 

Here is the product:


And her is the datasheet:


Communicates with your pc to control your robot
The wiimote is a really cool controller to use with your robots. It has many buttons, accelerometers and even a camera which tells the coordinates of the four … Read more

Linux crashing when reading from serial port, problem and solution

The problem:

I have a weather station project going on and I'm planning to use my Linux box for data logging. I have ATMega168 writing data to its USART, FT232R doing USB serial (see my first SMD soldering here: http://letsmakerobots.com/node/23323) and Ubuntu Linux logging data. Here's a simple picture of the setup:

Weather station data logging test setup

Serial Pins on AXE020


On the tutorial Picaxe for dummies Fritsl says the following:

Well, this is probably the simplest robot I've ever made. It is just this event's robot mounted in a old IBM box. I've built it just to serve as a testing platform … Read more
Controls arduino's Inputs and Outputs
UPDATE - 15 September 2010: Here is the second version.  No crossing lines this time, the digital pins are broken in two blocks, and the enumeration of them goes … Read more

serial uart with only rx or tx not both

Can I deliver serial data from one direction to enother (2 mcu) only with tx :

MCU1                                       MCU2




VB programming help wanted! Plotting serial data.

Hi guys, I`m attempting my own low speed arduino oscilloscope but have hit a brick wall with my mediocre programming skills. The arduino program and input stage works fine, it`s the PC software thats killing me.

Serrxd - Oh god nothing is happening

Trying my hand at making a computer interface for a PICAXE28x2. Plans are for it to send serial data through the programming cable and for that data to be interpreted and acted upon by the picaxe. To test how this serial communications works, i've set up the following code on the picaxe.



    serrxd b0
    if b0 = %00000001 then
    sertxd ("Recieved")
    end if

    goto interface


Navigates arround controlled by other computer
Using a
Hi, This is my newest project. It is basically formed by two 28x1that are serial controlled by a processing application, one for the motors and other for the two … Read more

Components to put bw 3.3v signal and 5v

I have an Arm based platform with Serial UART interface but in 3.3v level.

I want it to communicate with my Arduino.

I have a 3.3v power source in the Arduino(Dumilinove).

My question is what components to put between the 3.3v platform RX/TX and the Arduino RX/TX ?

Serial transmission and when to initialise it


 I am trying to figure out how to transmit data from one atmega to another one via IR. Oh btw i am using arduino language.

First thing i though of was setting the serial communication by using serial.begin in the setup function. I tried that and i noticed that the LED connected to the TX pin on the arduino lights up as soon as i give power to the atmega. This is not really what i wanted, cause i'd like to have the LED off when not in use.

How to hook up two serial outputs to one serial input

Hey all,

 So I'm working on a project where I'm using two processors and one of the things that I want to do is use one bluetooth device and have two microprocs communicate with it or send data through it. Of course this is not at the same time.

One chip would be the main com device, the other would send stored data when instructed to. I don't want to use one device as a passthrough as this would seem a little inefficient. so I came up with a schematic of what I think might work.

recieves commands sent by a computer thru a USB port and executes commands .
Using a
hello all ! , im new here and this is one advanced creation of mine which im going to submit here and follow up on its development . Read more

Calculon's Arduino Serial madness, part 2

Hello LMR,

Calculon has been tinkering with his Arduino for a few months now and he likes it. He is at the point where he is trying to get his 'duino to communicate with another device. His question is: HOW?!?!?

More specifically:

1. Does he use the Serial.print command? Serial.write?

2. How does he send more than one byte at a tyme?

3. Here's an example of the required byte sequence:

     in hex: 0x8D, 0x7F
     in decimal: 141, 127

Does he just send one byte, and then another? 

Arduino RF remote LCD display of Temparature & Humidity

Aim of Project :- Transmit via RF remote values of Temparature & Humidity to a LCD display.

Why:- because i have always dreaded sending floating point values to a LCD display and

wanted to carve it in stone for other projects i have lined up.

& Why :- RF Links are just so cool 8-P        500ft range is not to be sneezed at......

RF communication link between two Arduinos
This Tip/Walk-Through will guide you through a simple one way communication link between two Arduinos. The Project uses these RX/TX Radio Frequency (RF) Link … Read more

Parallel port control for a Mac

Anyone have experience with controlling a parallel (8 or more lines) output on a Mac (OS X)? I want to control my CNC machine with a parallel interface but Macs don't have parallel ports anymore. I need to find a suitable replacement, but a serial port/MCU would drastically complicate things. Please help! What hardware should I get?

Serial oscilloscope

Hi guys,

I'm currently programming a software oscilloscope based on C++ and DirectX, thus the performance is very good. It works directly off the serial/COM ports. I was just wondering..is anyone else interested in such a thing?

I'm programming it for my Arduino BUT it should be able to work with Picaxe(or anything else) too. It's not gonna be a fancy pro application, but it works pretty damn well :) For now it's rather limited since it only accepts 8 bit values...well for now...

Virtual Keyboard (Reads ASCII data from COM port)

Here is a program that reads Serial data, ASCII, and turns that into keyboard strokes. Works with the Serial.print command in the Arduino IDE. (Not sure how it works for Picaxe!)


About halfway down.. kind of hard to see the download link.

Using GPS via Serial Connection!

Well, I found out that Maplin had a really cheap GPS module that supports UART (Serial) at 38400 BPS. I'm still waiting for it, but here's what I have so far!

Here's the unit, and specs: (unit was JUST discontinued, so won't be able to find much info on the device itself)


Arduino Serial to Processing

Ok, thanks for helping me with my last question, but now I have another one...

I am currently trying to make a robot with a tactile switch at the front. When that tactile switch is pushed down the robot reverses and turns around. Here is the cool part though, when the switch is pushed down it will also send data to processing, causing a face to jitter onscreen. So far I have been able to make the code for the face jitter (except on mouse over) Here is the code if anybody is curious:

RS232 Communication with MCU

So I am making my own CNC - PCB Miller. It is communicating with the computer using RS232 (UART), but in my testing, I find that I don't always get the correct characters, even at 1200baud. Does anyone have a method to suggest for error-checking an incoming data string over serial? I was thinking of doing something like this:

CPU sends data to MCU 4 times.

MCU checks to make sure the data is repeated exactly 4 times.

--If yes->send "OK" 4 times

--If no->send "NOT OK" 4 times

If CPU receives OK, queue up the next data to send

Cuts shapes with better precision then me :D
Using a
Pictures:  - the front   - the back - left - right - the power unit Read more
I've found this multifunction chip on ebay,  the official webpage is http://www.web4robot.com/ I've just bought a pair, I'll come back to post with my … Read more