.\"	$NetBSD: mcpgpio.4,v 1.1 2022/01/17 16:31:23 thorpej Exp $
.\"
.\"Copyright (c) 2014 Frank Kardel
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.Dd January 10, 2022
.Dt MCPGPIO 4
.Os
.Sh NAME
.Nm mcpgpio
.Nd Driver for Microchip I/O Expanders on I2C and SPI bus
.Sh SYNOPSIS
.Ss I2C
.Cd "mcpgpio* at iic? addr ?"
.Cd "gpio* at gpiobus?"
.Ss SPI
.Cd "mcpgpio0 at spi? slave 0 flags 0"
.Cd "mcpgpio1 at spi? slave 0 flags 1"
.Cd "mcpgpio2 at spi? slave 0 flags 2"
.Cd "mcpgpio3 at spi? slave 0 flags 3"
.Cd "gpio* at gpiobus?"
.Sh DESCRIPTION
The
.Nm
driver supports the following Microchip I/O Expanders:
.Bl -tag -width "mcp23x08"
.It MCP23008
8-bit I/O expander, I2C interface
.It MCP23S08
8-bit I/O expander, SPI interface
.It MCP23017
16-bit I/O expander, I2C interface
.It MCP23S17
16-bit I/O expander, SPI interface
.It MCP23018
16-bit I/O expander, open-drain outputs, I2C interface
.It MCP23S18
16-bit I/O expander, open-drain outputs, SPI interface
.El
.Pp
Access to the pins is provided by the
.Xr gpio 4
interface.
.Pp
The SPI version of these devices support multiple chips per chip select
signal.
On the MCP23S08 and MCP23S17, this is achieved by tying the address select
pins to VDD or GND to select an address
.Pq 0-3 on MCP23S08 or 0-7 on MCP23S17 .
The MCP23S18 has a similar capability, but uses an analog voltage input
on a single address select pin, along with an internal voltage divider
ladder and a series of comparators to generate the 3 address bits; see
the data sheet for details.
The
.Ar flags
argument in the configuration directive for SPI attachments selects the
hardware address of the chip instance for that driver instance.
.Sh SEE ALSO
.Xr gpio 4 ,
.Xr iic 4 ,
.Xr intro 4 ,
.Xr spi 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Nx 7.0 .
It was overhauled in
.Nx 10.0
to support additional chip types and to add the I2C attachment.
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Frank Kardel Aq Mt kardel@NetBSD.org
and
.An Jason R. Thorpe Aq Mt thorpej@NetBSD.org .
.Sh BUGS
SPI instances of the
.Nm
driver do not utilize the Device Tree bindings for this device.
.Pp
The
.Nm
driver does not currently act as a GPIO provider for the platform
device tree.