Sunday, 9 December 2012

The Missing usb otg

I've been playing with some old nokia tablets (thats right not phones!) I've recently picked up a nokia n800 and an n810 for the retro handheld collection...(I think I need a display cabinet soon...) The n810 is great and actually has many uses for me day to day. I've been away this week and its made a good hotel wifi browser, great note taker  document tweaker with its nice hardware thumboard, and a useful link/transfer device when I needed to get some large audio files off my zoom recorders sd card and into my phone for a bit of on the fly editing. As a transfer device the n810 is very useful as it has 2gig of built in storage as well as an sd card slot....sort of....its a MINI sd slot (not micro) and amazingly I had a micro sd to mini sd adapter from an old phone. This means you can drag stuff off a card and back onto another card although I just did some big bluetooth transfers.

Anyway I was aware that with a USB on the go (otg) cable you can actually connect stuff to the 810 with the 810 acting as host...I hacked together a cable today and got this working (albeit a bit limited) it seems to only work for pendrives but for me thats really useful. I've been playing with powering usb hubs to try and get harddrives running to it but no luck as yet!

To make a USB otg cable you basically have to cut 2 cables in half one that has the micro b connection for the 810 and one that has a femal usb socket. Each cable end should have 4 wires, red, black, green and white and also a bare wire earth sleave wrapped round the other wires. Firstly you have to connect these wire to each other matching the colours and also connecting the earth wire. Then the slightly tricky bit is that the micro b end needs to be opened up (I carved the plastic back off the connector carefully using a razorblade). Once you have exposed the connections to the micro b socket you should discover you have one pin that is unconnected. (this is pin 4 and a lot of tutorials on making these just say to connect "pin 4" to earth...I think it easier to just find the only unconnected pin as it is ALWAYS pin 4 that is unconnected). So then with all the connections visible you want to solder a small wire to the unconnected pin and the other end to the edge of the metal socket housing therefore connecting pin 4 to earth. MAKE SURE that you now only use this for usb otg type operations as when you connect this cable it will want to put the device into host mode.

Anyway, I'll continue to tinker with the n810 and any more useful stuff will be posted.

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