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RoboLab for Commercial
Microcontrollers
By AJ Schrauth and Matthew Dombach
Summary:
The goal of this project is to explore
the integration of Robolab and the Lego RCX with commercial microcontrollers.
In doing so we hope to provide an option for students and educators
looking to use simple robotics in applications that require higher
performance than the RCX can deliver.
RCX Limitations:
The Lego RCX is an excellent development
tool for almost any low performance applications. Combining a microprocessor
with the quick mechanical design of Legos yields a system that can
be constructed in a matter of minutes. Add to this an intuitive
visual programming language, ROBOLAB, and you can design, build,
program, and test a robotic system in a matter of hours without
concern for compatibility. Unfortunately, this ease of use comes
with a price. For instance, the Lego RCX has a usable clock speed
(the rate at which it can perform tasks in the outside world) of
only 100 Hz. Most commercial microprocessors are capable of at least
10 MHz. Additionally, the RCX limits its user to three outputs and
three inputs. Standard microcontrollers are available with a myriad
of input/output configurations. The Z-World BL-1500 that we used,
for instance, has 24 digital input/output pins and 4 ADC input channels.
Furthermore, the Lego motors and three PWM output ports of the RCX
offer very little in terms of accurate and variable motor control.
Migration Difficulties:
The problem with moving from a Lego RCX and ROBOLAB
system to a commercial microcontroller is that there is a huge difficulty
gap between where a pure Lego system ends and a pure commercial
microprocessor system begins. This is because the Lego users are
protected from the headaches of industrial automation by both the
simple visual programming of ROBOLAB and the convenient, all-in-one,
package that is the RCX. In order to ease the transition between
systems, we decided that the next step would be to maintain the
use of ROBOLAB, but use it to drive a commercial microcontroller
rather than the RCX.
Our Solution:
We saw a few options for adapting ROBOLAB to
program additional microprocessor. The first option was creating
a new set of VIs (the ROBOLAB analog to functions in other languages)
that would allow the user to program for a target other than the
RCX. The main problem with this plan is that the user would have
to make an entirely new program to use the new microcontroller.
This removes the possibility of debugging the program with the RCX
before migrating it to the high performance microprocessor.
Instead we decided to use the LASM (Lego Assembly) code that ROBOLAB
generates to program the RCX. To do this, we created a C library
that defines functions for each LASM command. We also created a
new end VI for ROBOLAB. This VI takes the place of the 'stoplight'
in a regular ROBOLAB code and converts the LASM commands that the
user's program generated into C snytax. Once the LASM has been converted
it is saved to a C-file with the same name as the ROBOLAB program
and in the same directory as the ROBOLAB program.
In order to give the user as much control as possible, we also wanted
to allow them to configure the outputs and inputs of the microcontroller
through ROBOLAB. To do this, we developed a new project menu program
for ROBOLAB. This program allows the user to assign a ROBOLAB port
to each of Input/Output pins of the microcontroller and stores the
data to a configuration file. Our 'stoplight' VI then adds this
data to the beginning of the C-file.
With our system, a user can develop their program and test it with
the RCX. Then move it to a higher performance microcontroller by
changing only one VI in their program and configuring the microcontroller's
output ports. All that remains is the compilation and running of
a C-file. To get a better idea of the process we developed, please
check out this simple example.
Future Work:
We are currently looking into a few improvements
on this system. First of all, the we currently support only Inventor
Levels 1-3 in ROBOLAB. Unfortunately, Inventor Level 4 applications,
such as data logging and multitask execution, are where a user will
most likely need the extra performance offered by a commercial microcontroller.
Consequently, we are looking into expanding the C-library to include
Inventor Level 4 functions. Additionally, or current system only
supports one microcontroller, the Z-World BL-1500, and uses their
proprietary programming language, Dynamic C, as the output language.
It would be nice to add more microcontrollers to the list. Another
feature we would like to add is the ability for ROBOLAB to compile
and send code directly to the microcontroller rather than just outputting
a code file to be compiled and uploaded by the user.
Instructions:
This ROBOLAB add-on only works with the Z-World
BL-1500 and requires Dynamic C. We used Dynamic C version 5.26,
but new versions should work as well. Broader support is in the
works. In the meantime, follow these instructions to install Z-World
version:
1) Download the .zip file below
2) Move the 'Robolab.lib' file to the "***\lib"folder
where *** is the folder where Dynamic C is installed.
3) Use a text editor to open the "lib.dir" file that is
in the folder where Dynamic C is installed.
4) Add "LIB\ROBOLAB.LIB" as a new line at the end of that
file and save it.
5) Move the "MCend.vi" to the "***\engine\user.lib"
folder where *** is the folder where ROBOLAB is installed.
6) Move the "MCend.llb" to the "***\engine\project"
folder where *** is the folder where ROBOLAB is installed.
7) Develop your program in ROBOLAB using Inventor Level 4.
8) From the project menu select "Set MicroController Ports,"
configure the ROBOLAB ports to to the z-world pins you desire, and
press 'done.'
9) Replace the regular 'stoplight' VI with the "MCend.vi"
from the "My RCX Programs" folder on the Inventor 4 pallet.
10) Save your program and run it.
11) Open Dynamic C and open the C-file with the same name as your
ROBOLAB program. It will be in the same folder as your ROBOLAB program.
12) Compile, upload, and run the C program.
Click here to find
more pictures>>
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