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Thread: Teensy 4.0 ADC analog input multiplexer

  1. #1
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    Teensy 4.0 ADC analog input multiplexer

    Hi.
    I have a question before I order the T 4.0 board.
    I need to read 3 analog inputs. Are there any problems to alternate ADC between two terminals every second loop at 600MHz?

    Regards

  2. #2
    Senior Member+ Theremingenieur's Avatar
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    Depends on the loop timing, which means that depends on how time all the code in the loop() + occasional additional interrupts need.
    I'd suggest for the sake of clean (noise free) results and fixed bandwidth, that you start with the idea of a fixed sample rate, i.e. using a timer to trigger the ADC conversions (and the channel mux switching) periodically instead of letting a loop run freely and without control.

  3. #3
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    Ok, that I can do. Thank you
    Is it possible to get noise free result with 1000 samples per second for two analog terminals on one ADC?

  4. #4
    Senior Member+ Theremingenieur's Avatar
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    Quote Originally Posted by KRSO View Post
    Is it possible to get noise free result with 1000 samples per second for two analog terminals on one ADC?
    Yes. If all the common standards for noise free sampling are respected like clean grounding, low source impedance, and in some cases depending on the signals to be sampled a LPF with a corner frequency < fs/2 to avoid aliasing, are respected.

  5. #5
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    Define "noise free". IMO, the teensy4 ADC is pretty noisy. Oversampling + trimmed mean will help some.

  6. #6
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    If I can get as noise free readings from two terminals as what I would get from one at 1000 samples per second, I'm satisfied. I was only worried if it was possible to switch the multiplexer fast enough and get good readings.

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