ATmega328p using 8MHz internal oscillator about arduino-sdi-12 HOT 5 CLOSED

I've never tried the internal oscillator. It must be a bit inaccurate. You can try tweaking the bits per tick settings a bit to compensate.

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If you have an oscilloscope you could use that to test how inaccurate the internal crystal is so you know how much to adjust the timing by. You might also be able to see how much millis() differs from a stopwatch.

Also, double check that the prescaler settings are right for the internal oscillator. They might not be the same as when using a crystal.

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Thanks a lot for the suggestions!

I used a scope when I calibrated the oscillator. When I make the ATmega328p running the internal oscillator generate a SDI-12 message, it looks identical to the signal generated by any other SDI-12 device.

Checking the prescaler is a great idea! I will look into that this afternoon.

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From what I can see, the prescaler should not be impacted by the selection of an internal or external clock source. I will re-spin my boards to add an external oscillator, as I cannot afford to spend more time trying to get this to work. Thanks for the suggestions!

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Sorry!

You may be able to get it to work by going back to version 1.1.0, which was dependent on micros() instead of the timer/prescaler. I don't know how micros() is affected by internal clock accuracy.

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