microcontroller Can I cut off the 5v output of the IOIO to the Android


Posted on Feb 6, 2014

Project using Sparkfun`s IOIO for Android ( ) where power consumption is a concern. The IOIO board provides the phone with 500 mA charging if I`m correct, which is too much for continuous operation. There`s a trick I have in mind where I want to power the phone and the IOIO board separately from the same external power source (Of


microcontroller Can I cut off the 5v output of the IOIO to the Android
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course the phone gets its 3. 7v while the IOIO gets 5v). The catch here is that I want to cut off the 5v line on the cable from the IOIO to the phone, leaving the GND, Rx and Tx (Which are good enough for any serial transmission). USB doesn`t have the notion of TX and RX lines, it`s not a UART. The data lines are D+ and D- used for bidirectional differential signaling. The VBUS line (which you refer to as Vcc) is essential for detection the presence of the host (IOIO in this case), so what you`re suggesting will not work. The best you can do is use the current limiting trimmer that`s on the IOIO. Start with it fully clockwise, then, with the Android connected, turn it counter-clockwise until the connection drops, then back some. The minimum current that can be achieved like that varies by phone model. Also, turning the screen and comms off on the Android will reduce current significantly provided the phone battery is fully charged. @AhmedFarid Ytai`s answer is correct. The VBUS/VCC on the usb cable is required for the connection to work. The trimmer is the only way to change how much current draw is allowed. But the real question is, if you are powering both from the same external supply, why Are you regulating the 5v down to 3. 7v The phone would be more efficient at doing that itself from it`s normal 5v charging. Passerby May 29 `13 at 5:36 Never thought the creator himself would answer my question! I never noticed the...




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