CC3000 Connects but "Unable to retrieve the IP Address"

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digsigblake
 
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CC3000 Connects but "Unable to retrieve the IP Address"

Post by digsigblake »

I'm using
- A 9V, 1000 mA wall-wart power supply
- An Arduino Uno R3
- A ceramic antenna CC300 bought in the six months
- Arduino IDE 1.0.5
- buildtest sample code downloaded in the last week
- USB communication between my laptop and the Arduino.

The Arduino/CC3000/buildtest combo can consistently execute completely when we ask them to connect to a handheld Wifi hotspot we used in a debugging experiment; but they rarely execute successfully when we ask them to connect to my company's internal Wifi network.

When the company network is the target:
- Buildtest's connection step usually takes a long time (up to several minutes) to complete, and returns a return code of 1.
- As expected, buildtest then reports that it is making a DHCP request
- After announcing the DCHP request, buildtest almost always reports "Unable to retrieve the IP Address!" periodically forever; but sometimes that request succeeds and buildtest runs to a successful completion.

So... as the buildtest authors, do you have any insights that would help use the CC3000 and your library code in an environment where a connected CC3000's DHCP requests have a non-trivial chance of failing? I'm hoping your Wifi expertise is greater than mine.

Is the DHCP request something I should simply retry N times before declaring a hard failure?

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adafruit_support_mike
 
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Re: CC3000 Connects but "Unable to retrieve the IP Address"

Post by adafruit_support_mike »

If you can make a connection to a device nearby, the CC3000 and the code are probably working.

My guess is that the wifi signal is a bit weak, and the CC3000 is having a hard time making a reliable connection. Building-wide wifi systems tend to rely on the fact that the devices connecting to them will usually have large antennas and power budgets.

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digsigblake
 
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Re: CC3000 Connects but "Unable to retrieve the IP Address"

Post by digsigblake »

For those of us guessing that "that the wifi signal is a bit weak, and the CC3000 is having a hard time making a reliable connection." while trying to diagnose communication problems; have you folks at Adafruit (or anywhere else) used the CC3000's RSSI reports to develop a rule of thumb for deciding when a wifi signal is too weak?

I realize that the quality of the other device's antenna and related circuitry affects whether the other device can hear the CC3000 shield, but with that said; do you have any advice (other than "more is better") about go / no-go CC3000 RSSI thresholds for those of us looking at RSSI reports extracted from the CC3000?

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adafruit_support_mike
 
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Re: CC3000 Connects but "Unable to retrieve the IP Address"

Post by adafruit_support_mike »

I don't know of anyone using RSSI reports to estimate whether a connection will work, but I'll ask the team that works on the CC3000 library.

Part of the trouble is that the signal itself isn't the only parameter in play. The MTU (maximum transmission unit.. basically the size of the largest packet the CC3000 will send) also plays a big part in making a connection work. An RSSI level that can't support a 4906-byte MTU might work just fine (if a bit slower due to the extra overhead) with a 1024-byte MTU.

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adafruit2
 
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Re: CC3000 Connects but "Unable to retrieve the IP Address"

Post by adafruit2 »

the RSSI from the SSID scan comes from inside the module, there's no interpretation in the library so its kinda up to your setup to determine if its strong enough :)

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tdicola
 
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Re: CC3000 Connects but "Unable to retrieve the IP Address"

Post by tdicola »

You might check the CC3000 forums on TI's site too, they're good at getting a little more lower level info about the chip too: http://e2e.ti.com/support/wireless_conn ... f/851.aspx Unfortunately I haven't done much with RSSI myself either.

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