How to make your own write protect DIY style USB-Drive.
Posted 03 October 2014 - 10:15 PM
And you will probably also know, that this class of device is disappearing faster than VHS.
The crazy part about this is, that every controller chip used, still comes with the wp feature present.
So it's basically just a question of adding a switch at the right contacts.
Depending on the design of your USB-Stick finding a small enough switch or a suitable place to install it, may be the biggest challenge.
This however is completely up to you and not covered here.
But now to the electric part.
At first a disclaimer. Soldering on smd level is required! If you don't know, what you're doing, it is very possible to destroy your device. So exercise good judgement.
Now let's get started.
The first thing we need to know is, what controller resides inside our target device.
To figure this out we can either simply read what's written on the chip or use a software like 'chip genius', if we do not want to open the device yet.
Once we have the information, we need to find the data sheet for the chip.
We simply google it.
From the sheet we need the following data.
- which pin enables write protect (sometimes also labeled wp or w/p)
- if wp is high-enabled or low-enabled
- if it is high-enabled the positive power terminal of the chip
How to properly use the information?
High-enabled simply means, that wp is turned on when the pin is supplied with the correct voltage.
What is the correct voltage?
Well luckily we do not really need to know or care. We simply connect the wp pin via the switch to the positive power terminal of the chip. That has always the exact right voltage.
Low-enabled means, that wp is turned on when the pin is drained of its voltage.
We do this by simply connecting the wp pin via the switch to ground (GND).
Ground are always the wide circuit traces. It does not matter which or where we connect to.
That's it! Not really complicated, but very fiddlig.
And now ....
Last but now least ....
To the really cool thing about this ....
The same goes also for USB-Enclosures!!!
Yep, you've heard right, you can build your very own write protected USB-HDD or even USB-SSD.
Something that's not even on the market, as far as i know.
btw. Another advantage of the enclosures is, that they are pretty big and roomy in comparison. So way easier to find a right sized switch and place it.
Have fun with this little weekend project.
- RoyM likes this
Posted 04 October 2014 - 04:09 AM
Posted 04 October 2014 - 10:35 AM
But i'm not so sure about your switching diagram. It makes things a bit more complicated and i checked two of my USB-Sticks, which come with a wp-switch, before beginning the conversion. They both had simple open-close switches.
Just some points i like to clarify to any layman reading this thread.
- Adding a small resistor to the circuit is a good safety feature. I might will add it too.
- A rework station is a nice thing to have, but definitely not needed here.
A soldering needle or electronics soldering iron with temperature control are sufficient even with little experience.
- RoyM likes this
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