Renbotics - BLOG

GIT

by Adriaan | January 9, 2011

The latest versions of all Libraries, Hardware designs and Documents are now hosted at GitHub. https://github.com/renbotics

Robotic Arm Inverse Kinematics with Arduino and Servo Shield

by Adriaan | June 13, 2010

Circuits@Home replaced the control system of a Lynxmotion AL5D robotic arm with an Arduino and a Servo Shield. More information at Circuits@Home

Updated Servo Shield Library

by Adriaan | May 13, 2010

The Servo Shield library has been updated to fix a major bug relating to pin output mapping. Download revision 1.5

Back in stock

by Adriaan | May 10, 2010

The Renbotics Servo Shield is back in stock at SeeedStudio and now comes in red.

Arduino Servo Shield Sequencer with 256K External EEPROM

by Adriaan | October 18, 2009

The Servo Shield Sequencer works great for short sequences, up to 255 steps, but what if you need more than 255 steps? Change all bytes in the protocol to int and add more memory...

Ghetto Hax has a very good tutorial showing just how easy it is to add external I2C EEPRom to the Arduino. Within 10 minutes you can go from having only 1Kbyte of EEPRom on the Duemilanove to having 32Kbytes.

Arduino Servo Shield Sequencer Web Interface

by Adriaan | October 4, 2009

While the Renbotics ServoSequencer serial protocol works for displaying, adding and playing sequences it is not the most intuitive interface when showing off your skills.

To make things a bit more user friendly the Renbotics ServoSequencer Web interface was created.

Renbotics Servo Shield Sequencer

by Adriaan | September 20, 2009

While thinking of exciting things to do with the new Renbotics Servo Shield, I realized that most of them required some sort of sequencing. Google-ing did not result in much so I decided to create my own.

The first challenge was; how to store the sequence? I decided to use the on chip EEPROM and came up with this simple structure:

Position	Description	Type
0	Sequence count	byte
1	Length of memory used	byte
n	Sequence Number	byte
n+1	Sequence Length	byte
n+2	Sequence Interval	int
n+4	Step Number	byte
n+4	Servo Number	byte
n+5	Servo Positon	int

The first two bytes are used as a sort of allocation table to allow the system to know how many sequences there are and where the next available EEPROM byte is.

The next 4 bytes form the header of the sequence containing the sequence number, to allow multiple sequences to be stored, the amount of steps in the sequence, and the interval at which the steps should be executed.

The last 4 bytes are the step information containing the step number, servo number and position of the servo in that step. This information is repeated for each step/servo combination in the sequence.

Next, a way to program the sequences were needed, so I quickly hacked together a simple protocol: