» MAKE: NOISE — Discuss this article

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• 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

• 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

• 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

• 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

• 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

• 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

• 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