Make: Noise — Discuss this article

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• Finding Antique Voltmeter
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  Where can I look for an antique/old voltmeter? I tried Ebay and Google but neither yielded anything too promising. Any ideas would be appreciated.
  
  Velin

  Posted by veldel37 on September 02, 2008 at 19:47:13 Pacific Time

• Finding Antique Voltmeter
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  Flea markets? Junk shops? Old stereos? It's idiosyncratic. I got mine when my university physics dept. was throwing them out. I don't have an easy source, it just takes hunting.

  Posted by tigoe on September 03, 2008 at 11:43:36 Pacific Time

• Finding Antique Voltmeter
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  Thanks. I'll keep looking.

  Posted by veldel37 on September 04, 2008 at 17:23:06 Pacific Time

• PHP code
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  Hi, I am a novice to PHP, but it appears that the posted PHP code is incomplete?
  Thanks!

  Posted by bartj on September 12, 2007 at 09:28:13 Pacific Time

• PHP code
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  It looks like, in copying it from my site, someone forgot the opening comment bracket at the top:
  
  /*
  
  other than that, it's all there.
  
  

  Posted by tigoe on September 12, 2007 at 10:04:32 Pacific Time

• PHP code
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  I mean:
  
  Where is the opening PHP start tag
  "
  
  
  

  Posted by bartj on September 12, 2007 at 10:46:48 Pacific Time

• PHP code
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  Why, it's before the comment tag that got cut, of course!
  
  :)
  
  Should look like this:
  <?php
  /*
  Scrape AQI Page
  
  This program reads the Air Quality index page at
  
  http://airnow.gov/index.cfm?action=airnow.showlocal&cityid=164
  
  and removes everything but the values for particulate air quality and ozone level. It prints those two values in the following format:
  
  < particulate > followed by a linefeed character (ASCII 10)
  
  < ozone > followed by a linefeed character (ASCII 10)
  
  null character (ASCII 0)
  
  */

  Posted by tigoe on September 12, 2007 at 11:19:32 Pacific Time

• PHP code
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  Where is the opening Posted by bartj on September 12, 2007 at 10:44:36 Pacific Time

• One thing to try if you can't see the XPort on your network
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  Just want to say that if you're assigning (or attempting to assign) an IP address to your XPort dynamically via DHCP, it's good to have a little patience. In my setup it can take a good 30 seconds after power-up before the XPort has an IP and is visible on the network. Before I realized that I spent a bit of frustrating time powering things up, immediately checking for the device on the net, not finding it, cursing, powering everything down, rechecking my circuits and connections and then powering up and trying again.

  Posted by cspurgeon on September 11, 2007 at 18:15:51 Pacific Time

• xport http connection
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  First, thanks for this article. I've been wanting to do this since I first saw Tom's email clock.
  
  I'm having trouble with my xport HTTP connection. After reset, the arduino/xport will attempt to connect with the connection string "C255.255.255.255/80" (with my IP address). This is all that will happen - it seems to stall out here. To overcome this I have added some code in the (status==connecting) block:
  
  
if (inByte == 68) { // 'D' in ascii, disconnected
status = disconnected;
blink(3);
}
if (inByte == 78) { // 'N' in ascii, host unreachable
status = disconnected;
blink(4);
}

  
  This code says to start completely over if anythig besides a "C" is returned from the xport.
  
  With this code after reset, I get the following in arduino's serial monitor:
  
  C63.247.90.194/80
  C63.247.90.194/80
  GET /physical-computing/index.php HTTP/1.1
  HOST: www.markroland.com
  
  I got 3 bytes, total: 0 string: 128
  
  which is exactly what I want, however upon the next connection things start to go haywire:
  
  C63.247.90.194/80
  C63.247.90.194/80
  C63.247.90.194/80
  GET /physical-computing/index.php HTTP/1.1
  HOST: www.markroland.com
  
  I got 0
  
  There is nothing fancy going on with the PHP script, in fact all it does is echo "< AQI: 128>".
  
  The arduino code I'm using is posted here
  
  Using xport's web manager (not via telnet or serial as discussed in the article) I have set the xport's
  Channel 1 > Connection:
  Active Connection = Manual Connection
  Connect Reponse = Char Response
  Hard Disconnect = No
  
  I could use help understanding why the HTTP request works reliably the first run through the code but becomes unpredicatable after that. Ultimately I would like to use this setup to use a query string to save information to a MySQL database as frequently as possible.
  
  Final note: The arduino code posted on this page for Make does not include the function "stringToNumber" however I found it over on Tom's site, however on this code watch out because the HTTP request's new line characters aren't escaped! :)
  
  Okay, I realize that's a lot, thanks for any help!

  Posted by uci_acer on September 11, 2007 at 10:58:46 Pacific Time

• xport http connection
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  I seem to have struck a wall with this (at least until Tom's book arrives). I also seem to connect OK, but then I just get zero bytes back.
  
  I've tried tweaking the XPort's connection settings to see if that would make a difference. No luck. Here's a dump of my telnet session. Does this all look OK?
  

  
  
  Trying 192.168.1.104...
  
  Connected to 192.168.1.104.
  
  Escape character is '^]'.
  
  
  
  MAC address 00204A99C617
  
  Software version V6.1.0.0 (051122) XPTEXE
  
  Password :---
  
  Press Enter for Setup Mode 
  
  
  
  
  
  *** basic parameters 
  
  Hardware: Ethernet TPI
  
  IP addr - 0.0.0.0/DHCP/BOOTP/AutoIP, no gateway set
  
  Telnet config password set
  
  DHCP device name : not set
  
  
  
  *** Security
  
  SNMP is              enabled
  
  SNMP Community Name: public
  
  Telnet Setup is      enabled
  
  TFTP Download is     enabled
  
  Port 77FEh is        enabled
  
  Web Server is        enabled
  
  Web Setup is         enabled
  
  ECHO is              disabled
  
  Enhanced Password is disabled
  
  Port 77F0h is        enabled
  
  
  
  *** Channel 1
  
  Baudrate 9600, I/F Mode 4C, Flow 00
  
  Port 10001
  
  Connect Mode : D4
  
  Send '+++' in Modem Mode enabled
  
  Auto increment source port disabled
  
  Remote IP Adr: --- none ---, Port 00000
  
  Disconn Mode : 48
  
  Flush   Mode : 00
  
  Terminal name: lantronix
  
  
  
  *** Expert
  
  TCP Keepalive    : 45s
  
  ARP cache timeout: 600s
  
  High CPU performance: disabled
  
  Monitor Mode @ bootup : enabled
  
  HTTP Port Number : 80
  
  SMTP Port Number : 25
  
  MTU Size: 1400
  
  Alternate MAC: disabled
  
  Ethernet connection type: auto-negotiate
  
  
  
  *** E-mail
  
  Mail server: 0.0.0.0
  
  Unit       : 
  
  Domain     : 
  
  Recipient 1: 
  
  Recipient 2: 
  
  
  
  - Trigger 1 
  
  Serial trigger input: disabled
  
    Channel: 1
  
    Match: 00,00
  
  Trigger input1: X
  
  Trigger input2: X
  
  Trigger input3: X
  
  Message : 
  
  Priority: L
  
  Min. notification interval: 1 s
  
  Re-notification interval  : 0 s
  
  
  
  - Trigger 2 
  
  Serial trigger input: disabled
  
    Channel: 1
  
    Match: 00,00
  
  Trigger input1: X
  
  Trigger input2: X
  
  Trigger input3: X
  
  Message : 
  
  Priority: L
  
  Min. notification interval: 1 s
  
  Re-notification interval  : 0 s
  
  
  
  - Trigger 3 
  
  Serial trigger input: disabled
  
    Channel: 1
  
    Match: 00,00
  
  Trigger input1: X
  
  Trigger input2: X
  
  Trigger input3: X
  
  Message : 
  
  Priority: L
  
  Min. notification interval: 1 s
  
  Re-notification interval  : 0 s
  
  
  
  
  
  Change Setup:
  
    0 Server
  
    1 Channel 1
  
    3 E-mail
  
    5 Expert
  
    6 Security
  
    7 Defaults
  
    8 Exit without save
  
    9 Save and exit            Your choice ? 1
  
  
  
  Baudrate (9600) ? 
  
  I/F Mode (4C) ? 
  
  Flow (00) ? 
  
  Port No (10001) ? 
  
  ConnectMode (D4) ? 
  
  Send '+++' in Modem Mode  (Y) ? 
  
  Auto increment source port  (N) ? 
  
  Remote IP Address : (000) .(000) .(000) .(000) 
  
  Remote Port  (0) ? 
  
  DisConnMode (48) ? 00
  
  FlushMode   (00) ? 
  
  DisConnTime (00:00) ?:
  
  SendChar 1  (00) ? 
  
  SendChar 2  (00) ? 
  
  
  
  Change Setup:
  
    0 Server
  
    1 Channel 1
  
    3 E-mail
  
    5 Expert
  
    6 Security
  
    7 Defaults
  
    8 Exit without save
  
    9 Save and exit            Your choice ? 9
  
  
  
  Parameters stored ...
  
  Connection closed by foreign host.
  
  

  
  

  Posted by cspurgeon on September 19, 2007 at 07:23:18 Pacific Time

• xport http connection
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  Try making a test server on your laptop and setting the Xport to connect to that. That way you can see all the bytes being exchanged between server and Xport, and see if there's something missing. LIkewise, you can write a test HTTP client to see what the server's sending. It's possible there's a byte missing somewhere that one side or the other is waiting to see; either the Xport/Arduino combo isn't sending some termination that the server wants, or the reverse. I have examples of test servers and clients on my code blog at tigoe.net/pcomp/code

  Posted by tigoe on September 19, 2007 at 07:51:44 Pacific Time

• xport http connection
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  Quick answer, so I don't know if I'll be able to help properly, but:
  
  If you're seeing the CXXX.XXX.XXX.XXX/80 string a few times, that might mean that the server's responded, but the LTRX isn't properly acknowledging the connection. I seem to remember seeing this once after writing the article. I think I improved the code for the net meter in the book, which is coming soon, but I'm sorry, I forget the details at the moment. The trick is, find a way to make sure the server's not confused by extra connect strings. Might want to look at the server logs, if you can, to figure that out. The 0 returned was my clue on that. Shouldn't get that if there's no connect.
  
  re: stringToNumber, I wrote that because the version of Arduino I was working in at the time didn't have the atoi() function in its C libraries (I wrote the article around Arduino 005 or 6, I think). It had been cut to save space on the code download. David Mellis later worked magic on the libraries, and put that function back in. So you can just use the standard C atoi() function now. You'll see that in the book too.
  
  Anyway, hope that helps. If not, I know the longer explanation in the "Making Things Talk" book will help. Good luck!
  
  

  Posted by tigoe on September 11, 2007 at 11:30:24 Pacific Time

• Powering the XPort device via the Arduino 5V source
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  OK, I've almost got this puppy working. I'm powering the Arduino board via an external 9V power supply, and I was hoping I could then use the board's 5V power source to power the XPort (the XPort documentation says that while it calls for 3.3V power supply it can handle 5V) but when I connect it to the Arduino's 5V it doesn't seem to work. (The XPort *does* work if I drive it with a couple of AA batteries as the power source). Does the Arduino's 5V source just lack the power to run the XPort?
  

  Posted by cspurgeon on September 05, 2007 at 01:12:18 Pacific Time

• Powering the XPort device via the Arduino 5V source
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  No, the Xport's voltage regulator should be able to supply the necessary current, as long as your 9V supply supplies enough current. I recoommend something beefy, like 800mA or greater.
  
  Also, I know the XPort docs say it can handle 5V, but I find that it tends to overheat and behave erratically on 5V, so I really recommend using a 3.3V regulator in between the XPort and the 5V.

  Posted by tigoe on September 05, 2007 at 03:34:36 Pacific Time

• Powering the XPort device via the Arduino 5V source
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  Ooh, that's good to know about the voltage! The device I'm building will run unattended for long periods, so I'll definitely toss in a voltage regulator. The 9V power supply I'm using to power the Arduino claims to be 800mA, so we'll see if the 3.3V output has enough oomph. Thanks again!

  Posted by cspurgeon on September 05, 2007 at 09:04:11 Pacific Time

• Powering the XPort device via the Arduino 5V source
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  Sorry, could you be a bit more specific!?! I'm new to all this malarkey and I'll need to try to track down the part online. As it is, I think I'm going to order the bits and pieces from US websites and get them shipped to the UK.
  
  Cheers
  aw

  Posted by AndrewWestley on September 08, 2007 at 13:09:29 Pacific Time

• Powering the XPort device via the Arduino 5V source
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  Specific about which part? the 3.3V regulator? I use the LM7833, which I usually order from Sparkfun, but there are several others you can use.
  
  If you're interested in a more basic guide, I can recommend a book on it:
  http://tinyurl.com/ytgy2t
  :)

  Posted by tigoe on September 10, 2007 at 09:21:11 Pacific Time

• Help w/ scaling
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  I don't own an Arduino yet, but it should be arriving any day, so this question is based a bit on ignorance:
  
  I studied the Arduino code and I can't quite understand the conversion between AQI and voltage. The code states:
  meterMax 165 (this is to peg the meter?)
  meterScale 150 (meter reads 0-150...got that)
  And the conversion function:
  airQualityValue = desiredValue * meterMax/meterScale
  
  So let's take an AQI of 80. According to the formula, we have 80 * (165/150) = 88, so 88 is what is sent to the meter pin. I'm sure this is where I go screwy -- Arduino can write "analog" values of 0-255 to the PWM digital ports, resulting in voltages from 0-5v. 5v/255 steps = roughly 0.02 V/step. With that logic, doesn't a value of 88 equate to about 1.75 volts, which equates to...er...about 88 on the scale? Thinking aloud here, I wouldn't expect any conversion using the given scale. An AQI of 50 unconverted and written to the meter pin as "50" (*.02 volts per step) would result in 1 volt output to that pin. Isn't that what we need? What am I missing here? I understand the concept of scaling, but I can't see how it applies here since it seems to skew the results. Thanks for the help!!

  Posted by geobarefoot on August 27, 2007 at 16:47:24 Pacific Time

• Help w/ scaling
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  2 things to keep in mind:
  
  1. The meter's physical movement in response to PWM is not exactly linear.
  
  2. I am not an engineer, nor a very good mathematician. I messed with the formula until I was happy with the aesthetics of the meter movement.
  
  I didn't take a mathematical approach to it. I tried a few different formulae across a few different inputs until I got one that looked right on my meter. It's likely going to look different on your meter, particularly if yours is an antique like mine. So I suggest taking an experimental approach to the formula. Mess around until it looks the way you want it to. You can test it by sending in different values from the PHP script. Then when you know what you like, let the real values come in from the AQI page.

  Posted by tigoe on August 27, 2007 at 19:34:53 Pacific Time

• Help w/ scaling
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  Great, Tom. Thanks for taking the time to read and answer my question. I particularly like "messed with the formula until I was happy with the aesthetics of the meter movement". Suits me to a T. Can't wait to get my Ardi in the mail.
  -Steve

  Posted by geobarefoot on August 28, 2007 at 09:18:38 Pacific Time

• Which Lantronix product?
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  Looking at the Lantronix website, there are several variations in the XPort product line. Which is the (best/correct) one to get?

  Posted by cspurgeon on August 21, 2007 at 09:58:04 Pacific Time

• Which Lantronix product?
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  I tend to get part number XP1001001-03R from www.semiconductorstore.com, and an Rj-45 breakout board from Sparkfun

  Posted by tigoe on August 21, 2007 at 10:30:38 Pacific Time

• Which Lantronix product?
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  Got it. Thanks Tom!

  Posted by cspurgeon on August 21, 2007 at 16:49:23 Pacific Time