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Diffstat (limited to 'docs/library/machine.rst')
| -rw-r--r-- | docs/library/machine.rst | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/docs/library/machine.rst b/docs/library/machine.rst index 753f6b417..c6da71585 100644 --- a/docs/library/machine.rst +++ b/docs/library/machine.rst @@ -118,12 +118,15 @@ Miscellaneous functions microseconds. The `pulse_level` argument should be 0 to time a low pulse or 1 to time a high pulse. - The function first waits while the pin input is different to the `pulse_level` - parameter, then times the duration that the pin is equal to `pulse_level`. + If the current input value of the pin is different to `pulse_level`, + the function first (*) waits until the pin input becomes equal to `pulse_level`, + then (**) times the duration that the pin is equal to `pulse_level`. If the pin is already equal to `pulse_level` then timing starts straight away. - The function will raise an OSError with ETIMEDOUT if either of the waits is - longer than the given timeout value (which is in microseconds). + The function will return -2 if there was timeout waiting for condition marked + (*) above, and -1 if there was timeout during the main measurement, marked (**) + above. The timeout is the same for both cases and given by `timeout_us` (which + is in microseconds). .. _machine_constants: |