It’s now my third day with the Z2, and therefore it’s time to begin with some hardware hacking.
As I now have plugs for the extension connector, I’ll start to play around with this.
At the extension connector of the Z2, you have the signals of the USB controller and a 3.3V supply, amongst many others. But the standard supply voltage is 5V, and most of the USB devices will not run from 3.3V. So we would need a boost converter, that generates 5V out of 3.3V to drive USB devices.
On the other hand, most USB devices are in fact 3.3V, and have their own voltage regulator on board. So, if you bypass the voltage regulator, the device should be fine with only 3.3V.
Lets try this out.
I disassembled a cheap minuscule USB bluetooth plug. One of those, you can buy for 3$ or so.
As you can see, it’s really tiny and packed with electronics components.
Here are the two sides of the PCB in detail:
The next step was to solder a USB cable to the connector pads of the plug, in order to measure the voltages at the pins of the voltage regulator.
I plugged the cable into an USB port, and the module started to work, as i could see by the blinking activity LED.
Here you can see the connections to the USB cable:
On the other side you can see voltage regulator and the voltages at it’s pins.
Also you can see the activity LED.
In the next step, I desoldered the voltage regulator, and soldered a wire from 5V input to 3.3V output.
Remember to not connect the stick to USB after the modification! You will destroy the bluetooth chip!
Here are two pictures of the PCB without the voltage regulator.
You may ask, why my LED is lit up. I said don’t connect to USB.
Well, to test if the complete stick would run from 3.3V, I placed the regulator I had just removed in series with the stick. This simulates the conditions that it would see when connected to the Z2.
See it here:
And it worked!
So I’m now sure that this stick will also work when it’s connected to a Z2 and powered by 3.3V.
Next step: Fitting this inside an extension connector plug.