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Author Topic: DAC and analog pins floating problem (at HIGH and LOW state)  (Read 1126 times)
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Hi guys,
this is my first post here and I am sorry if this will be kind of noob question.

So I have next problem. When I am testing my Ax in DACx PINs at digitalWrite(pin, HIGH/LOW) or analogWrite(pin, 0/255), I get too high/low values. I measured output voltage with oscilloscope with one COM to Arduino GND and A probe to xx PIN.
at A0-11 I get aprox. 70-90mV at digitalWrite(pin, LOW) or analogWrite(pin, 0) and aprox. 3200mV at digitalWrite(pin, HIGH) or analogWrite(pin, 255)
at DAC0-1 I get aprox. 550mV at digitalWrite(pin, LOW) or analogWrite(pin, 0) and aprox. 2750mV at digitalWrite(pin, HIGH) or analogWrite(pin, 255)
Interesting thing is that PWM pins 2-13 works OK and digitalWrite(pin, LOW) or analogWrite(pin, 0) gives aprox. 10mV while digitalWrite(pin, HIGH) or analogWrite(pin, 255) gives aprox 3300mV.

What could be source of this problem. Is my Arduino damaged? I tested PINs because my application was not working as it should be. I am reading FSR through inst amp. After short time output from inst amp rise on aprox 2.2V. I also have high power led (1,5W), and if I stop supplying this led, then inst amp output doesn't rise.
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I'm sure to affirm that's DAC0-11 output is correct.
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You mean DAC0-1 or A0-11?

So I suppose minimum voltage at DAC is 550mV?
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The DAC pins output from 1/6th to 5/6th of Vcc - they do not do the whole range
and are designed for audio processing really.  The DAC is also a poor performer
with sparkle codes from what I can tell - its accuracy is more like 9 bits than 12
because of this.
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Thank you for explanation smiley
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