Matthieu WENZEL

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10 years, 2 months ago.

NUCLEO ADC not working well when the board isn't USB powered

I am using analog_read_u16() which works perfectly when my nucleo is USB powered, but as soon as I use an external power supply ,the value read by the adc are bad. The voltage which is apply on the ADC doesn't change but the value which is return by the function analog-read-u16() do change. What's the problem ?

2 Answers

Geremia G
10 years, 2 months ago.

Hi,

i faced the same issue http://developer.mbed.org/questions/4500/Just-a-note-about-STlink-when-not-usb-po/ The STlink own led draws current when blinks and your ADC input get offsetted. Wire up an external switch with couple of wires to RST/SB11 solder-jumper on bottom of the stlink, close it when externally powered, so stlink is put in permanent reset and does not blink its own led.

Accepted Answer

Thanks for your answer , I'll try this.

posted by Matthieu WENZEL 21 Oct 2014
Peter Drescher
10 years, 2 months ago.

If you plan to use the board without the PC you can cut off the STLink. For programming you can use CN4 with 5 cables.