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.Dd November 6, 2021
.Dt PCF8591 4
.Os
.Sh NAME
.Nm pcf8591
.Nd driver for the PCF8591 8-bit A/D and D/A converter
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device pcf8591"
.Cd "device iicbus"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
pcf8591_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver supports reading four inputs and setting one output over I2C.
The hardware supports configuring the input lines as:
.Bl -bullet
.It
four single-ended inputs
.It
three differential inputs (one input line is shared between all three inputs)
.It
two single-ended inputs and one differential input
.It
two differential inputs.
.El
.Pp
The
.Nm
driver reports data via
.Xr sysctl 8
entries in the device's node in the
.Xr sysctl 8
tree:
.Bl -tag -width inputs.%d
.It Va inputs.%d
The input level of the corresponding input in steps between 0 and 255.
Absolute voltage depends on an actual reference voltage.
.El
.Pp
On an
.Xr FDT 4
based system the following properties must be set:
.Bl -tag -width "compatible"
.It Va compatible
Must be set to "nxp,pcf8591".
.It Va reg
The I2C address of
.Nm .
It should be in the range from 0x40 to 0x4f (7-bit).
.El
.Pp
The DTS part for a
.Nm
device usually looks like:
.Bd -literal
/ {

	...
	pcf8591adc {
		compatible = "nxp,pcf8591";
		reg = <0x48>;
	};
};
.Ed
.Sh SEE ALSO
.Xr fdt 4 ,
.Xr iicbus 4 ,
.Xr sysctl 8
.Sh HISTORY
The
.Nm
driver and this manual page was written by
.An Andriy Gapon Aq Mt avg@FreeBSD.org .
.Sh BUGS
The
.Nm
driver does not support changing the input configuration.
All input lines are configured as single-ended inputs.
.Pp
The
.Nm
driver does not support setting the output.
It is always disabled (tri-state).