Pololu Wixel - Manual (Page 24)

The Wixel can be powered from USB.
3V3 Power Output
The Wixel’s 3V3 pin gives access to the output of the Wixel’s 3.3 V regulator. If the Wixel’s power supply drops
below approximately 3.5 V, the 3V3 output will be less than 3.3 V. Normally this output can provide up to 150 mA,
but if the Wixel’s power supply is above 5 V then it is limited to 100 mA. You can use 3V3 to power your own 3.3 V
devices.
VALT Power Output
VALT provides access to the input pin of the Wixel’s 3.3 V regulator, which is connected through a diode to VIN or to
the USB bus voltage, depending on which power source is connected. You can use VALT to power your own circuits
as long as you do not draw more than about 500 mA.
For example, if you leave VIN disconnected, VALT can power 5V devices.
Low Power Considerations
The CC2511F32 is capable of a sleep mode (PM2) where the chip draws less than 1 μA and is still capable of
waking itself up. Without modifying the Wixel’s hardware, it is possible to power it from VIN and get the current
consumption down to around 100 μA. Most of that current is consumed by the Wixel’s 3.3 V regulator. To get rid
of it, you will need to sever the output pin of the regulator and power the Wixel directly from the 3V3 pin with a
2.0–3.6 V power supply. For details on how to do this, please contact Pololu.
Please note that currently none of the Wixel apps support low power modes, so the Wixel will draw approximately
30 mA at all times. To make your Wixel operate with low power you would have to write your own app or modify
one of the existing apps. You will need to make sure that all of the I/O lines are either outputs or get pulled high or
low: an input line at an intermediate voltage can consume several microamps of extra current.
5.b. Connecting a Microcontroller via TTL Serial
If you have loaded a Wixel app that employs one of the Wixel’s two UARTs (such as the Wireless Serial App
[http://www.pololu.com/docs/0J46/9.b] ), then the Wixel can communicate with another microcontroller via asynchronous,
non-inverted TTL serial. Communication between the Wixel and an RS-232 device requires additional hardware.
Pololu Wixel User's Guide © 2001–2014 Pololu Corporation
5. Connecting Your Wixels Page 24 of 64