Archive for the ‘FIRST’ Category

Winpdb Remote Debugger for Python ported to RobotPy on vxWorks

Tuesday, January 11th, 2011

I’m really excited about the idea of using python on our FIRST Robotics Team’s Robot this year, and one of the first things that got really annoying was the lack of debugging capability, since vxWorks doesn’t really have a console (I mean it does, but in the way that FRC has it setup, its not really a console in the traditional sense of the word). So I searched around and found Winpdb, a pretty neat remote debugger for python. So after playing with it for a bit, I’ve got it working on RobotPy and it seems to do the trick so far. :)

I’ll be creating some other tools as needed, so watch for more python in the future!

Download: http://www.virtualroadside.com/FRC/

Posted in FIRST, python | No Comments »

cRio Netconsole implemented in Python

Friday, November 12th, 2010

The FIRST Robotics Competition uses the NI-cRio platform for the controller for the robots in the competition. There is a bit of functionality called ‘NetConsole’ which sends the stdout from vxWorks out to a waiting client (refer to the WPI FIRST website for instructions to enable this). It turns out that the protocol used to implement the NetConsole for the cRio is incredibly simple… it just sends the raw output data as a bunch of UDP packets out to the broadcast address on port 6666 (which I suppose is slightly amusing). Here’s a dirt-simple python script that catches the output (TODO: need to send it input… haven’t gotten around to looking at that yet). 

#!/usr/bin/env python

import socket
import select

UDP_PORT=6666

sock = socket.socket( socket.AF_INET, socket.SOCK_DGRAM, socket.IPPROTO_UDP )

sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
sock.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
sock.bind( ('',UDP_PORT) )
sock.setblocking(0)

while True:
    result = select.select( [sock], [], [] )
    msg = result[0][0].recv( 8196 )
    print msg

Posted in FIRST, General, python | No Comments »

Changing variables using a web interface and embedded HTTP server

Tuesday, April 21st, 2009

When walking around during the Boston Regional, I had been talking to some people about code, and they mentioned that LabView was great because they could tune their PID controllers on the fly while the robot was operating. So I thought to myself, “why can’t I do this with C++?”. And… so I did. WebDMA was created to allow our FIRST Robotics team to tune our robot in an easy to use and intuitive way via any modern web browser.

Using C++ operator overloading, WebDMA provides proxy objects that your application can use as normal variables which can be manipulated or displayed by your application via a configurable jQuery/javascript powered Web 2.0 interface hosted by an lightweight embedded web server.

Despite that WebDMA was specifically created for use in FIRST Robotics on the NI-cRio/vxWorks platform, it uses the Boost ASIO portable networking library and Boost Thread portable threads library and is usable on any platform supported by these Boost libraries (tested on Boost 1.38, requires a patch for vxWorks).

A non-functional (but very shiny) demo of the interface is available at http://www.virtualroadside.com/botface/index.html

Visit the Google Code project site for WebDMA

Update: Go here for a video: http://www.virtualroadside.com/blog/index.php/2009/04/25/webdma-demo-video/

Posted in FIRST, Howto, Innovation, Javascript, jQuery, Software, WebDMA | No Comments »

WPILib Test Harness Released!

Saturday, March 14th, 2009

So after *far* too much time spent on this, I am happy to announce the release of my WPILib Test Harness! For those who aren’t aware, WPILib is the name of the C++ library that FIRST gives to FIRST Robotics Teams to control the robots. The control system is a PowerPC running on a cRio platform designed and produced by National Instruments.

It had occurred to me towards the end of the build season this year that it was really annoying that I could only easily test code while our team was meeting, and of course I stay up late (as evidenced by this post time). So I wrote some stubs, but at some point I realized it would just be easier to make a giant stub for WPILib, since its just a set of classes with some hardware interfaces. It was extremely useful, and as I evolved it I was even able to find bugs in WPILib and the program for our bot.

At some point I decided to bring it in the direction that it is now, and I’ve spent the last week adding things and making the GUI a bit shinier. I’m pretty happy with the results so far, but theres a long way to go before every bot program will run under it. There’s a lot of things that do work, but there’s also a lot of things that don’t work.
(more…)

Posted in FIRST, Software, WPILib | 1 Comment »

Swerve Drive Model Spreadsheet

Monday, March 9th, 2009

Our robot this year uses a ‘swerve drive’ mechanism, with 4 independently steerable wheels. I wasn’t quite sure exactly of the best way to describe the robot’s motion in terms of basic parameters (speed, heading, rotation) , so I went google searching. I found a PPT by Ian Mackenzie talking about different types of omnidirectional drive systems, and it was extremely helpful.

After thinking about it some more,  I created this spreadsheet to help describe the motion parameters to the students I was working with. Its pretty sweet — it uses scatter plots to show the angle of each wheel and the ideal velocity to obtain the motion desired based on the speed/rotation/angle parameters of the overall robot motion. The implementation in C++ was straightforward after that, and it worked out extremely well (unfortunately there is the whole issue of controlling it intuitively with a joystick… we haven’t quite got that down yet).

Download it at my FRC resources download page

Posted in FIRST | No Comments »

FRC Driver Station Test Program

Sunday, March 8th, 2009

This is another resource that I’ve created for the Kwarqs FIRST Robotics team this season that I’ve found useful, and hopefully others will find it useful as well.

This particular program is stupidly simple, but really nice to have around in case you think your driver station is being screwy, or you want to verify that your switches work *before* running your actual code on it (not that you would run something without testing it, right? ;) ). As you can see from the code, it displays the driver station inputs on the LCD panel of the driver station. It uses a modified version of the DriverStationLCD class posted at http://thinktank.wpi.edu/article/144

(more…)

Posted in FIRST | No Comments »

PID parameter calculation spreadsheet

Thursday, January 29th, 2009

While working on some code for the FIRST team that I’m on, I had decided we were going to need PID control for some portions of our robot. Unfortunately, I have not done a lot of this stuff.. I took a control systems theory class in college, but I never quite saw the value of it at the time (which, I’ve come around now that I’ve seen some practical applications). So, to understand how it works more, I created this spreadsheet with adjustable P/I/D parameters.  I found this to be a useful tool in understanding the output of a PID control system.

Of course, its strictly an ideal model and not particularly realistic (try setting the P parameter to 1)… but its primarily useful for getting that basic understanding. Theres a number of ways it could be improved… feel free to improve it. :)

Download the PID spreadsheet

Posted in FIRST | 1 Comment »

Updates and such

Tuesday, January 6th, 2009

Well, I have a *ton* of things going on right now… I am very busy mentoring for a FIRST team that my company sponsors (the Kwarqs), and some important deadlines coming up at work.. and trying to get my massive updates to Roadnav integrated in.

Speaking of which, I’ve bundled all of my R* and B+ tree code into a library called libsdbx… I need to write more in depth about it, but its a nice header-only C++ library that allows usage of generic R* and B+ trees with either a memory backend or a file-based backend. Its really nice to use, but I think I’m going to hold off on releasing it in a formal package until a final release of libroadnav is created (which will definitely iron out any lingering performance issues or bugs).

Libsdbx can be found in Roadnav SVN at https://roadnav.svn.sourceforge.net/svnroot/roadnav/libsdbx/trunk/.

As I create neat FIRST-related stuff, I’ll be sure to post some of that up here also. I’m really excited about this open source thrust that FIRST seems to be going down lately, its definitely encouraging and makes me want to contribute.

Posted in FIRST, roadnav | No Comments »