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Mar 22, 2013, 04:53 AM
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Maxbotix vs wifi

So the Maxbotix actually took off & after bouncing off the floor & ceiling a few times, held the altitude at 0.5m, when it worked. It couldn't do 1m. The problem is it's jammed by wifi. Unlike the USB host jamming I2C when wifi was on, this was a real RF interference problem. No voltage ripple appeared when wifi was on.

The RC filter made no difference, but it did work when a probe was connected to it & ground. Disconnect the probe from either 3.3V or ground & jamming resumed. It didn't matter if the probe was connected to the oscilloscope. The probe must have shifted the resonant frequency of the susceptible Maxbotix part or injected an out of phase waveform. Throwing in a low ESR 10uF didn't work.

Connecting the wifi to an umbilical cable & moving it away worked. Maxbotix worked best when wifi was right next to the motors & completely died when wifi got 1/2 way from a motor. With wifi yet another problem for the Maxbotix, it continues to be a real turd. But to be sure, no-one else in the world ever put a Maxbotix on a wifi aircraft.

After this problem, all the other systems are known to be working with wifi, but there are some huge problems making wifi unviable in a product. The ground station has to be running before associating the access point, because of the inability of the USB host to transmit without 1st receiving.

So the parallax weighs 9g & the Maxbotix weighs 4.3g without the RC filter. It's heading back towards not another STM32 ground station but a raspberry pi routing wifi to 900Mhz. Not the most effecient or cost effective solution but it's the easiest to use.
Last edited by Jack Crossfire; Mar 22, 2013 at 06:32 AM.
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