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S2 on Sale for under $90 — Parallax Forums

S2 on Sale for under $90

WhitWhit Posts: 4,191
edited 2011-12-06 18:12 in Robotics
Great price on the S2 (without adapter and USB cable)... Get one and be impressed!

http://www.parallax.com/Store/Robots/AllRobots/tabid/755/ProductID/712/List/0/Default.aspx?SortField=ProductName,ProductName
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Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-11-23 20:07
    The USB adapter and cable, purchased separately, are only another eighteen bucks combined:

    -Phil
  • WhitWhit Posts: 4,191
    edited 2011-11-23 20:35
    Excellent point Phil! A must have, if don't already have it. And still a deal...

    Happy Thanksgiving!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-24 13:10
    Yea! I just ordered one.

    I'll need to go back and read Whit's article again.

    Thanks for the heads up about this.
  • WhitWhit Posts: 4,191
    edited 2011-11-24 13:20
    You'll really enjoy playing with this Duane! It is a lot of robot for the money...
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-24 13:41
    I'm looking forward to playing with it.

    I keep meaning to try to understand the motor control code Phil wrote for it. I figure it will be easier to understand his software, if I have identical hardware.

    Your nicely curved beanie hat was very impressive. It's obvious the Scribbler has very good motor control algorithms.

    I've been toying with my own motor control software using encoders and my robots don't have nearly the control the Scribbler appears to have. It's time for me to learn how to do this stuff correctly.
  • Ken GraceyKen Gracey Posts: 7,392
    edited 2011-11-24 13:43
    Hey turkeys,

    Don't buy all of these because our next batch doesn't arrive until August 2012, and we'll be out for quite a while before that shipment arrives. :smile:

    Ken Gracey
  • ercoerco Posts: 20,256
    edited 2011-11-24 14:06
    Ken Gracey wrote: »
    Hey turkeys,

    Don't buy all of these because our next batch doesn't arrive until August 2012, and we'll be out for quite a while before that shipment arrives. :smile:

    Ken Gracey

    Shoot. There are only 1779 units in stock. I was gonna buy them all, but per Ken's request, I'll hold off for now.
  • doggiedocdoggiedoc Posts: 2,241
    edited 2011-11-24 14:34
    erco wrote: »
    Shoot. There are only 1779 units in stock. I was gonna buy them all, but per Ken's request, I'll hold off for now.
    LOL erco! I had the thought of buying a large quantity and donating to a local School Robotics club in an effort to gain favor in Matt's QuadRover contest. Alas, I don't think any of the schools in my district have a Robotics club.
  • ercoerco Posts: 20,256
    edited 2011-11-24 14:46
    I think there are many great minds at work trying to gain favor in Matt's QuadRover contest.

    Look how much effort just goes into suggesting product names! I bet some really good stuff will happen in the name of free Quadrovers.
  • doggiedocdoggiedoc Posts: 2,241
    edited 2011-11-24 15:13
    Honestly, I may just buy one before they're all gone. I've been wanting to, but can't think of a way to expense it on the Hospital's books. If I donate an equal value of S2s as a advertising campaign perhaps that might float. But and that's a big But, is that enough of a Publicity stunt for the contest. As you said: "there are many great minds at work trying to gain favor in Matt's QuadRover contest" and I suspect I'd be outclassed.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-24 15:16
    doggiedoc wrote: »
    I've been wanting to, but can't think of a way to expense it on the Hospital's books.

    Just use it as a syring transporter. I'm going to use mine to transport test tubes in my lab.
  • doggiedocdoggiedoc Posts: 2,241
    edited 2011-11-24 15:47
    Duane Degn wrote: »
    Just use it as a syring transporter. I'm going to use mine to transport test tubes in my lab.
    Perhaps an autonomous dog walker? Hey! That could work!!
  • ercoerco Posts: 20,256
    edited 2011-11-24 16:33
    Duane Degn wrote: »
    Just use it as a syring transporter. I'm going to use mine to transport test tubes in my lab.

    If Jessica can send paper messages with an S2, it can certainly transport some syringes or test tubes!
    http://www.youtube.com/watch?v=8RFa1qFgxv8
  • doggiedocdoggiedoc Posts: 2,241
    edited 2011-11-24 16:47
    erco wrote: »
    with an S2
    ... I thought we were talking about QuadRovers.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-11-24 17:45
    I see now, you were talking about a QuadRover. I was talking about a S2.

    @erco, I just finished watching that video. Pretty cool.
  • doggiedocdoggiedoc Posts: 2,241
    edited 2011-11-24 18:24
    @ Duane - I just had a silly vision of a large dog fleeing with an S2 dangling in the wind on a leash! LOL
  • WhitWhit Posts: 4,191
    edited 2011-11-25 08:43
    The point is that at this price, you can get an S2 for the price of a Scribbler! Buy em up! Ken will make more...
  • ercoerco Posts: 20,256
    edited 2011-11-25 09:03
    doggiedoc wrote: »
    @ Duane - I just had a silly vision of a large dog fleeing with an S2 dangling in the wind on a leash! LOL

    This AIBO on steroids could take a hundred S2's for a drag... http://www.youtube.com/watch?v=4u7aIIUDSQk

    Don't get your finger pinched in a leg joint.
  • doggiedocdoggiedoc Posts: 2,241
    edited 2011-11-25 11:01
    @erco - they even roll over! LOL Hey, if I had a few of those as patients, I could expense out a lot of my Parallax and Radio Shack purchases!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-02 15:04
    The postman just brought my S2. I was sure I had enough charged batteries but I was wrong. I'll test it out once the batteries are charged.

    It's a nice looking little robot.
  • WhitWhit Posts: 4,191
    edited 2011-12-03 15:10
    Are you playing yet Duane?
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-03 21:00
    Whit wrote: »
    Are you playing yet Duane?

    Thanks for asking. Yes, I'm playing.

    I've been looking for your articles. I couldn't find them on Parallax's website so I'll look through my Servo magazines (they were in Servo right?).

    Edit: It's in Sept/Oct 2011 Robot magazine

    I'm better at selecting the demos now that I've learned to use enough light for the sensors.

    It doesn't seem fair to have a robot that can already avoid objects and detect when it's stuck without any building or programming. Not fair, but it is fun.

    I still don't really own it yet. I haven't voided the warranty. I don't feel like I own something until I've voided the warranty.

    I should get around to opening it up (voiding the warranty) soon.

    I also received an "Inventor's Wand". I was very pleased to see how precise the ruler is.
    Edit: Move "Three Laws" comment to Inventor's Wand thread.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-04 09:13
    Once I found your Scribbler 2 article in the Sept/Oct Robot magazine, I remembered also finding it when I was looking through the Scribbler 2 download page.

    Here's the direct link to the article. (I don't know if you have to have a Robot subscription to read the article online or not.)

    I've got to figure out a good Cub Scout demo for the S2 so I can show it off at a Pack Activity or a Pack Meeting. (I'm a new Cubmaster.)

    I could have the Cub Scouts lay a line with electical tape for the S2 to follow. I'll need to think about this.

    @Whit, Thanks for pointing me to the sale. I felt bad when I missed the $99 introductory price. I'm glad I didn't miss this chance to get a S2 for $89.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-12-04 09:24
    Duane,

    For success in line-following, I would recommend against using electrical tape, since it's so shiny. Parallax sells a 1/2"-wide black masking tape that's optimal for line following, here:

    It also has the advantage of not leaving a residue when pulled up.

    If Parallax is sold out, you can get the same tape from McMaster Carr (#76265A1).

    -Phil
  • WhitWhit Posts: 4,191
    edited 2011-12-04 17:10
    Glad you're having fun Duane!

    Phil is right about the tape.

    For some fun projects, check out Jessica's videos on the S2 resource page.
    See http://forums.parallax.com/entry.php?211-S2-Robot-Messenger-Bots
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-04 20:33
    @Phil, Thanks for the info about the tape. The tape will like be used on the church's floor so I ought to be extra careful about not leaving any residue.

    @Whit, Yes, I saw Jessica's fun video.

    I just reread this old thread. It's much more interesting to me now.

    I need to figure out how to use the hacker port correctly. I'm guessing the level shifter needs to be turned on or something. I'm trying to add a Nordic transceiver, which has 5V tolerant IO, without any luck yet. The 3.3V is conveniently located at test point 21 (gound is test point 11 or one of the many hacker port ground pins).

    It sure looks like there's a lot going on on those circuit boards.

    Off to look at the S2 object for hacker port clues (feel free to drop some clues here).

    Has anyone come up with a good way of getting 3.3V signal lines out from the S2's Prop?
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-04 20:47
    Okay, I found the problem (I think). The hacker port couldn't keep up with the fast SPI use with the Nordic module.

    I changed the clock mode to " _clkmode = xtal1 + pll1x", and I was able to communicate with the Nordic module. The only other multiplier I've tried so far is 16 (which didn't work). I'm betting I can run the Prop faster than 5MHz; I'll just need to experiment a bit.

    Edit: I'll likely just slow the Nordic driver down a bit. I plan to use the S2 at 80MHz.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-04 22:35
    I found something I don't like about the S2. The hacker port.

    I really wish Parallax hadn't used the level shifter. Even if I bypass the level shifter by soldering wires directly to the Prop, the level shifter still messes up fast SPI communication.

    I can understand why the level shifter was used. I figure it was to keep the S2 backwards compatible and to make sure the S2 could drive hobby servos (I have a few that don't like a 3.3V signal).

    I'm pretty sure I don't need the level shifter for any of my sensors or other items I might want to attach to the S2. I'm planning on removing the level shifter along with the resistors and capacitors that go with it. Can anyone give me a reason not to do so?

    I'll wait until tomorrow to preform the surgery. If anyone knows of a reason this isn't a good idea, please let me know.

    I'll likely replace the chip with just some wires. I can add a series resistor when I need to communicate with a 5V device.

    I could only use the Nordic modules (with my original driver) with the Prop running at 10MHz or slower. I did get the modules to work at 80MHz by adding some NOPs to the SPI driver.

    I eventually want to make a boot loader with these Nordic modules so I can program the Prop wirelessly (like Phil has done with the XBees). I'm pretty sure I'll want all the speed these modules will give me when it comes time to program the Prop wirelessly. Another reason to want the increased wireless speed is to transmit audio (I haven't done this yet but another forum member has).

    So surgery in the morning unless there's a good reason to leave the level shifter in place.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-12-05 11:38
    Duane,

    Before you go hacking into the hacker port, take a look at the datasheet for the level translator:

    There you will see that the pullups on the output can be made much stiffer than the ones provided in the S2. Adding an external 1K pullup will change the normal TC (4.7K * 1nF = 4.7 µs) to 825 ns. If you're driving a cable, be sure to put the paralleled pullup at the other end for maximum noise immunity.

    -Phil
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-12-05 12:33
    Phil Pilgrim (PhiPi) wrote: »
    Duane,

    Before you go hacking into the hacker port, take a look at the datasheet for the level translator:
    There you will see that the pullups on the output can be made much stiffer than the ones provided in the S2. Adding an external 1K pullup will change the normal TC (4.7K * 1nF = 4.7 µs) to 825 ns. If you're driving a cable, be sure to put the paralleled pullup at the other end for maximum noise immunity.

    -Phil

    Phil,

    Thank you for the datasheet. I've been reading it a bit.

    I've decide to leave the level shifter for now. I'd like any hacks I make to be easy for others to reproduce. I don't want others to remove their level shifters just to try out the things I do.

    The nRF24L01+ modules I'm using now cost less than $3 each shipped. I attached one to the inside of the S2 with some double sided foam tape. My plan is to use two of these modules and a QuickStart board to make a little remote control for the S2. (I also have another remote in the works.)

    I'll post code one I get it working correctly. Hopefully it wont be hard for others to duplicate the remote.

    I've decided not to worry about the speed issue with the S2 hacker port. I'll just slow the driver down enough so it will work with the S2. I'll leave streaming audio and other high speed transmissions for my other robots.

    Again, thank you for the information Phil. The stuff you told me about additional pull-up resistors is just at the edge of my understanding (or at edge of my not understanding). I figure there's a good reason to add the 1nF capacitors to the buffer lines. My guess is it was to reduce noise problems. But I suspect those capacitors slow down the transmission speed over those data lines.

    I assume the 4.7us has something to do with the slew rate. 4.7us seems high to me. The driver I slowed down only sets the clock high for 100ns. Although now I don't remember if I tested the slow driver on the 5V side of the buffer or the 3.3V side. (I think it was the 5V side.)

    Don't feel obligated to teach me this stuff (though I'm all ears). I think I know enough to get these modules to work with the S2.
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