Category Archives: ftdi serial to usb

Getting rid of unused COM ports in Windows

Ok, this isn’t new, but Windows has the memory of an elephant, and remembers serial dongles that no longer exist. I was up to COM21 and only had two external USB-serial dongles, so it was time for housecleaning.

Found this page that absolutely was spot-on and that I’d never have divined on my own. I think it was the combination of running Device Manager as Administrator, and that’s apparently not straightforward to do (even though I have admin privileges).

After deleting 6 GPS serial instances,  8 FTDI instances, and another 5 Prolific instances, I rebooted the box, waited for it to find the two USB-serial adapters, and now am happily back to COM3 and COM4.

Small victories are good.

Update on wardriving/walking/cycling setup

The stackup that I did inside the enclosure was fairly crude. The GPS receiver and its attached antenna are at the “top” of the stack, and stuck to the inside uppper surface of the enclosure using double-sticky foam tape. Immediately below that, the dual-band Wi-Fi board is component-side down. I’d removed both the SMA-RP female and the USB male board connectors to reduce height and length. The bottom of the stack is the USB hub, again with USB female sockets removed and component side down as there’s two electrolytic caps that stick up 8 mm or so.

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I’ve used double-sticky foam tape for things like this over the years, and as long as it doesn’t absorb moisture, it’s quite RF-transparent and the antenna has no issues.

The Wi-Fi board has a ground-plane on top and bottom, but I wanted to reduce to a minimum any local fields from the components, so the board goes in component-side down to isolate it (maybe a bit) from the GPS antenna.

The GPS receiver itself is completely encased in a shield, and is slightly larger than the antenna, so there may be some added attenuation of spurious emissions from the Wi-Fi getting into the GPS.

The USB hub, at the very “bottom”, also has a top/bottom ground plane.

The Wi-Fi sniffing performance is as good as my permanent mobile setup, and the GPS gets excellent PDOP (<2.0) when there’s a decent field of view of the sky.

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The apps used to grab the GPS data is 4river’s NMEA Monitor, a fine little program.

Trimming the fat from my wardriving setup

As you may remember, several weeks ago I wrote about my soon-to-be wardriving setup that centered around my new TW700 Winbook. I had a cheap USB hub, a TP-Link dual-band Wi-Fi stick, and an EM506 GPS receiver.

I finally took some time on Saturday to get rid of the fat, i.e., all the individual plastic housings, the USB connectors themselves (physically large and limited my layout options), and am about to repackage the whole thing into a single weathertight enclosure that can either be attached via magnets to the top of the rental cars or carried in a backpack/fannypack as I walk around an area.

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Here’s the setup without all the excess plastic. The GlobalSat EM-406A (SiRF Star III) modular GPS is at the left, with its built-in antenna the white/beige square; the TP-Link dual-band Wi-Fi dongle has been reduced to just the board, and as well I removed the USB connector to reduce the length; the USB hub has had the two dual-port USB assemblies removed to reduce height; and all the former USB connections have been reduced to bits of ribbon cable. The TP-Link dual-band antenna is quite good and so I’ll be keeping that. The 3′ USB hub cable still needs to be replaced with a 6′ version, and I think I’ll remove the RP-SMA connector from the side of the TP-Link and directly connect the coax to the board.

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The most difficult thing so far has been removing the excess USB paraphernalia and cleaning up the board. To that end, yesterday I bought a new tip for the soldering station, and more 63/37 solder. I use a solder sucker to remove the existing solder, but have found it’s quite difficult with the RoHS solder used nowadays. The 63/37 solder seems to dilute the RoHS solder and make it easier to remove with the solder sucker.

Today I’ll finish this up and put it in an enclosure.