I need help... If U can measure the voltage on every mbed pins. Just take voltmeter, power on mbed without any program and please measure for me the voltage of all pins... I don't know, if I could damage my mbed somehow, or what, because my disabled pins are 2.2V, but if I enable it (DigitalOut...), they work fine...
Please, try to do it for me... So, if you do it, it should look like this: VB-__V; nR-__V; p5__V; p6__V; etc.
Thank you very much
What do you mean by "disabled"? And what voltage did you expect?
I mean unused or unspecified in any program. And I expect 0V on p5-p30 and other pins I don't know, I expect nothing... I just need compare voltage of pins, when is mbed powered on but without any running program. Here are my voltage measures of pins (powered by USB): VB, nR -> 3.3V; p5...p30 -> 2.2~2.3V; D+ -> 3.3V; D- -> 0V; TD+...RD- -> 3~3.3; IF+ -> 3V; LED1...LED4 -> 0V
Hi Bo Ni,
If you want to do real measurements on pins, use an osciloscope instead. This will show you the real signal on a pin. It may not be a constant signal (ie steady 2.2 volt) but pwm like. A voltmeter will only measure the average signal level.
About the voltages you measured: Have a look at de LPC datasheet (somewhere to be found on this website). It explains how the input/output circuit arond a pin is build up. If a pin is not used in any way it may just float, giving an undefined voltage based on very small leak curent in this circuitry. So if you have something special in mind to do with youre unused pins, use them in your program and set them to the state you need.
Hi, I am back with some new knowledge and skills (few custom designs), thanks to mbed :)
Of course thank you for reply. I found somewhere in the LPC176x User Manual notice about pullups - and it says something like "undefined pins are pulled up", that is the unknown voltage I measured :)
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