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AD7747 recover from power-down mode

Question asked by Idowu on Apr 15, 2015
Latest reply on Apr 17, 2015 by jcolao

Hello,

 

Problem:

I get repeated measurements when I use power-down mode (Measurement does not change). When I don't power-down, the measurements change accordingly, as expected.

 

Application:

I'm using two AD7747 (CDC) for liquid level sensing. My application is required to minimise power consumption therefore I like to put my AD7747 on power-down mode while waiting for the next measurement cycle. My sample rate is 150ms. I set the CDCs to single-conversion mode or continuous mode before taking a new measurement. And power-down after measurement.

 

Code fragment:

    // READ CAP SENSOR VALUE

    digitalWrite(SDA_SWITCH_PIN, SENSE_DOWN);

    writeRegister(REGISTER_CONFIGURATION, _BV(5) | _BV(1)); // single conversion mode at 124ms conversion time.

    int cap_down = (int)((float(readValue())/16777215)*16*100);

    writeRegister(REGISTER_CONFIGURATION, _BV(1) | _BV(0)); // power down.

    //

    digitalWrite(SDA_SWITCH_PIN, SENSE_UP);

    writeRegister(REGISTER_CONFIGURATION, _BV(5) | _BV(1)); // single conversion mode at 124ms conversion time.

    int cap_up = (int)((float(readValue())/16777215)*16*100);

    writeRegister(REGISTER_CONFIGURATION, _BV(1) | _BV(0)); // power down.

 

Question:

How can I recover from power-down mode? I have tried using delays (for up to 1sec) to ensure the CDCs is fully awake but had no luck.

Any solution to this problem?

 

Thanks.

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