some current sense amplifiers have a non zero offset voltage
that correlates to zero current. adding this offset voltage binding
allows the driver to be used with this type of circuitry.
Signed-off-by: Brandon Allen <brandon.allen@exacttechnology.com>
ADC output values can have noise, even if the input is 0V. Add a noise
threshold so that raw ADC readings below the threshold can be zeroed
out. By default the threshold is disabled.
Signed-off-by: Jordan Yates <jordan@embeint.com>
Request calibration on ADC samples to improve the accuracy of the ADC
outputs and therefore the final measured current.
Signed-off-by: Jordan Yates <jordan@embeint.com>
Change the unit of the sense resistor in the devicetree binding from
micro-ohms to milli-ohms. This is done for three reasons.
Firstly, the maximum value resistor that can currently be represented
is 4.2 kOhms, due to the limitation of devicetree properties to 32 bits.
Secondly, storing the resistance at such a high resolution makes
overflows much more likely when the desired output unit is micro-amps,
not milli-amps.
Finally, micro-ohms, are an unnecessarily precise unit for the purpose
of these calculations, and a resolution that is not realistic to
achieve. The high resistor resolution results in large divisors that
reduce the resolution of outputs. Unlike resistors characterised down to
the micro-ohm, devices wanting to measure micro-amps are actually
realistic.
Signed-off-by: Jordan Yates <jordan@embeint.com>
When a sensor that depends on an ADC is enabled in devicetree, enable
the ADC subsystem. ADC is roughly equivalent to a bus for these sensors
(the mechanism through which data is transferred), which had the same
conversion applied in #48707.
The same benefits apply here, namely removing the need for the following
pattern in board `.kconfig` files:
```
configdefault ADC
default y if SENSOR
```
Signed-off-by: Jordan Yates <jordan@embeint.com>
