Shop OBEX P1 Docs P2 Docs Learn Events
question about stamp for quadcrawler — Parallax Forums

question about stamp for quadcrawler

joe from NYjoe from NY Posts: 22
edited 2005-12-15 15:18 in Robotics
Hi, Been interested in building a robot kit. I think i will purchase a Quad crawler kit.

I see it comes with the BS2 stamp chip.

My question (after comparing PIC vs Stamps vs OOPIC) is this controller powerful enough for this robot·leaving ·room for expansion? (arms, speech ,etc)

I am asking this as I understand the basic stamp does not have interupts. Does this lack of interupts cause problems with programming robots of this size??

Please enlighten me on this subject [noparse]:)[/noparse]
·

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2005-12-14 21:51
    The BS2 has a very nice, simple PBasic language. Note the device costs $50 each (and the Pro programming board costs $10.00). This is a very low cost of entry.

    The BS2 cycles at about 2000 Basic Instructions Per Second. This is MUCH faster than people think. This is MUCH slower than most microprocessors (a typical PIC has a 20 Mhz clock, but takes 4 clock cycles to do anything, so cycles at 5 MIPS -- however, these are PIC assembly instruction MIPS, not full Basic instructions).

    A PIC only has one level of interrupt, so its interrupt useage is problematic to begin with.

    The BS2 is a single-tasking processor, so when it is 'listening' on a SERIN instruction, it can't drive the wheels. However, using Airplane Servo's, you refresh the servo position signal every 20 mSec, so you CAN drive multiple servo's in a program loop. In other words, there are very effective work-arounds for this single-tasking nature.

    The BS2 only has 26 bytes of RAM, but 2000 bytes of EEPROM. This can be a limitation.

    Conclusion: People usually start out using the BS2, because it is extremely reliable, requires little battery power, and is extremely easy to program for proof-of-concept devices. If they run out of 'horse-power', they've at least proved out the hardware, and can transition to more native PIC solutions. Note these "native PIC solutions" usually have a much more expensive development system, but can be cheaper for many copies.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-12-14 22:55
    Or you can transition over to the SX Microcontroller for which we provide free software tools for, and you can get 50 - 75 MIPS (million instructions per second)...· =)·


    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
    csavage@parallax.com


    Post Edited (Chris Savage (Parallax)) : 12/15/2005 3:24:56 PM GMT
  • ForrestForrest Posts: 1,341
    edited 2005-12-15 00:02
    FYI the servo's on the Quadcrawler are controlled by the Parallax Servo Controller (PSC) that works in conjuction with the BS2. This setup free's up the BS2 so it can handle other tasks such as the IR sensor.
  • joe from NYjoe from NY Posts: 22
    edited 2005-12-15 00:04
    allanlane5, Thanks for your input. Got the idea of how it works.

    I guess if the quad crawler is sold with the bs2, it must suffice for such a kit.

    Anyone here build a QUADCRAWLER?>
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-12-15 15:18
    Hello everyone,

    ·· To clarify my previous post (Which was mis-interpreted), all of our software and documentation is freely available on our website.· It so happens that programming the SX requires one piece of additional hardware (The SX-Key), which obviously isn't free.· I apologize for any misunderstanding that may have caused.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
Sign In or Register to comment.