[MSP430F2013] Sample voltage of output pin with the SD16_A

Sam FIsher

Hello,

I want the measure the brightness with a photodiode with the SD16_A and wanted to use the attached circuit. I want the possibility to turn the photodiode-circuit off to save power. I taught I set P1.7 as an output and low during the measurement, otherwise high. I want to measure the voltage drop on the resistor.

Will this work or is it impossible the measure the voltage of a pin configured as output?

Thank you

over 8 years ago

0 Sam FIsher over 8 years ago

Prodigy 30 points

Sorry, I forgot the circuit: s27.postimg.org/.../SD16_A.png

0 Leo Bosch over 8 years ago in reply to Sam FIsher

Guru 23000 points

Your hardware setup is correct, but be sure that the voltage at Vdd not exceeds Vcc.
You don’t need to have P1.7 as an Input configured only as a normal digital Output, and when you not enable the analogue function (AE) on this pin A3- is connected to Vss which will be (nearly) the same level as the Low level at P1.7 (digital out = low), some difference might occur (depends on series resistor and temperature) which you can calibrate away.
AE for P1.6 must be set.

0 Dennis Eichmann over 8 years ago in reply to Leo Bosch

Guru 74080 points

And choose your setup right so you will stay within the ADC's input voltage range:

0 Leo Bosch over 8 years ago in reply to Dennis Eichmann

Guru 23000 points

Dennis, the current is very little, it’s more likely he needs the PGA to amplify an not to attenuate the input voltage.

0 Sam FIsher over 8 years ago in reply to Leo Bosch

Prodigy 30 points

So if I set SD16AE3 to zero the Pin works like a normal digital output and A3- it internally connected to Vss?

Thank you.

0 Leo Bosch over 8 years ago in reply to Sam FIsher

Guru 23000 points

This is correct.

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[MSP430F2013] Sample voltage of output pin with the SD16_A