diff options
Diffstat (limited to 'docs/library')
| -rw-r--r-- | docs/library/pyb.DAC.rst | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/docs/library/pyb.DAC.rst b/docs/library/pyb.DAC.rst index fd786b63b..3e236a3da 100644 --- a/docs/library/pyb.DAC.rst +++ b/docs/library/pyb.DAC.rst @@ -49,7 +49,7 @@ To output a continuous sine-wave at 12-bit resolution:: Constructors ------------ -.. class:: pyb.DAC(port, bits=8) +.. class:: pyb.DAC(port, bits=8, \*, buffering=None) Construct a new DAC object. @@ -60,12 +60,27 @@ Constructors The maximum value for the write and write_timed methods will be 2\*\*``bits``-1. + The *buffering* parameter selects the behaviour of the DAC op-amp output + buffer, whose purpose is to reduce the output impedance. It can be + ``None`` to select the default (buffering enabled for :meth:`DAC.noise`, + :meth:`DAC.triangle` and :meth:`DAC.write_timed`, and disabled for + :meth:`DAC.write`), ``False`` to disable buffering completely, or ``True`` + to enable output buffering. + + When buffering is enabled the DAC pin can drive loads down to 5KΩ. + Otherwise it has an output impedance of 15KΩ maximum: consequently + to achieve a 1% accuracy without buffering requires the applied load + to be less than 1.5MΩ. Using the buffer incurs a penalty in accuracy, + especially near the extremes of range. + Methods ------- -.. method:: DAC.init(bits=8) +.. method:: DAC.init(bits=8, \*, buffering=None) - Reinitialise the DAC. ``bits`` can be 8 or 12. + Reinitialise the DAC. *bits* can be 8 or 12. *buffering* can be + ``None``, ``False`` or ``True`; see above constructor for the meaning + of this parameter. .. method:: DAC.deinit() |