--- /sys/man/3/spi	Sat Feb 13 00:00:00 GMT 2021
+++ /sys/man/3/spi	Sat Feb 13 00:00:00 GMT 2021
@@ -0,0 +1,66 @@
+.TH SPI 3
+.SH NAME
+spi \- access to the main Raspberry Pi SPI interface
+.SH SYNOPSIS
+.B bind -a #π /dev
+.PP
+.B /dev/spictl
+.br
+.B /dev/spi0
+.br
+.B /dev/spi1
+.SH DESCRIPTION
+The Broadcom SoC on the Raspberry Pi has three SPI interfaces:
+the main SPI interface, designated SPI0, and two auxiliary SPI
+interfaces, designated SPI1 and SPI2.
+On the first generation Pis, only SPI0 was brought out to the
+header on the board.
+For the B+ and Pi2 models, SPI0 and SPI1 are available.
+The driver described in this man page only supports SPI0.
+.PP
+Reads and writes to the files
+.B spi0
+and
+.B spi1
+transfer data over the SPI bus.
+Accesses to
+.B spi0
+cause the transfers to take place with the CE0\_0 line asserted
+low.
+Similarly, transfers to
+.B spi1
+are carried out with CE1\_0 asserted low.
+.PP
+The
+.B spictl
+file is used to set various control parameters.
+It accepts the following commands:
+.TP
+.BI clock " freq"
+Set the frequency of the SPI clock.
+The clock from which the SPI clock is derived runs at 250MHz,
+and the divisor must be a multiple of 2.
+(The Broadcom documentation incorrectly says "power of 2".)
+The driver sets the divisor to the highest multiple of 2 that results
+in a clock rate that is less than or equal to the
+.I freq
+parameter in MHz.
+.TP
+.BI mode " n"
+Treats
+.I n
+as a two-bit number specifying the settings for the clock phase
+and clock polarity.
+The default value of 0 matches the polarity and phase requirements
+of most peripheral devices.
+.TP
+.B lossi
+Enable a bidirectional mode where the MOSI line is used for both
+reads and writes.
+.SH SOURCE
+.B /sys/src/9/bcm/devspi.c
+.br
+.B /sys/src/9/bcm/spi.c
+.SH BUGS
+The various SPI modes are untested and the LoSSI support is
+unimplemented.
--- /sys/man/3/gpio	Sun Jan 10 00:00:00 2016
+++ /sys/man/3/gpio	Sun Jan 10 00:00:00 2016
@@ -0,0 +1,99 @@
+.TH GPIO 3
+.SH NAME
+gpio \- access to Raspberry Pi GPIO pins
+.SH SYNOPSIS
+.B bind -a #G /dev
+.PP
+.B /dev/gpio
+.fi
+.SH DESCRIPTION
+.I Gpio
+serves a single file that provides access to the GPIO pins on the
+Raspberry Pi.
+Reads from the file receive a 16-character hexadecimal string
+representing a
+.B vlong
+giving the values of up to 64 GPIO lines.
+(The processor on both the first and second generation Pis provides
+54 actual GPIO lines.)
+The proper method for sampling GPIO 27 is as follows:
+.IP
+.B read(gfd, buf, 16);
+.br
+.B buf[16] = 0;
+.br
+.B gvals = strtoull(buf, nil, 16);
+.br
+.B "pin27 = gvals & (1 << 27);"
+.PP
+Writes to
+.B gpio
+control the characteristics and output values of GPIO lines.
+The exact operation is specified by one of the following commands:
+.TP
+.BI function " pin f"
+Set the function of GPIO
+.I pin
+to
+.I f.
+The valid values for
+.I f
+are:
+.BR in ,
+.BR out ,
+.BR alt0 ,
+.BR alt1 ,
+.BR alt2 ,
+.BR alt3 ,
+.BR alt4 ,
+.BR atl5 ,
+and
+.BR pulse .
+The functions
+.B in
+and
+.B out
+set the specified GPIO line to be a general purpose input
+and output, respectively.
+The various
+.BI alt n
+functions are as specified in the Broadcom documentation and
+differ on a per-pin basis.
+The
+.B pulse
+function is somewhat specialized.
+It causes the pin to be set to an output for
+2μS and then to be set to a input.
+With the value of the line set to 0 and a pullup resistor on the
+line, this operation provides a short low pulse suitable for bit-banging
+a 1-wire interface.
+.TP
+.BI pullup " pin"
+Enables the internal pullup resistor for the specified GPIO pin.
+.TP
+.BI pulldown " pin"
+Enables the internal pulldown resistor for the specified GPIO pin.
+.TP
+.BI float " pin"
+Disables both internal pullup and pulldown resistors for the specified
+GPIO pin.
+.TP
+.BI set " pin value"
+For GPIO pins set to the output function, this command sets the output
+value for the pin.
+The
+.I value
+should be either 0 or 1.
+.SH NOTES
+All pin number references are according to the SoC documentation.
+These GPIO signal numbers do
+.I not
+match the pin numbers on the header on the Pi board.
+Reads sample the external signal values.
+As a result, the values read for output pins might not match
+the value written to them if externally they are driven harder
+than the SoC drives them.
+.SH SOURCE
+.B /sys/src/9/bcm/devgpio.c
+.br
+.B /sys/src/9/bcm/gpio.c
--- /sys/man/3/i2c	Sun Jan 10 00:00:00 2016
+++ /sys/man/3/i2c	Sun Jan 10 00:00:00 2016
@@ -0,0 +1,85 @@
+.TH I2C 3
+.SH NAME
+i2c \- basic I2C interface
+.SH SYNOPSIS
+.B bind -a
+.BI #J n
+.B /dev
+.PP
+.BI /dev/i2c. n .ctl
+. br
+.BI /dev/i2c. n .data
+.fi
+.SH DESCRIPTION
+.I I2c
+serves a one-level directory with two files
+that give access to the target device with address
+.I n
+(given in hexadecimal)
+on the system's I2C bus.
+.I N
+is usually determined by the I2C device manufacturer.
+I2C gives address 0 special meaning as the `general call' address.
+See an I2C specification for details.
+.PP
+The control file
+.BI i2c. n .ctl
+accepts commands to set the valid address range and
+subaddressing mode for the corresponding data file.
+The following control messages can be written to it:
+.TP
+.B a10
+Force 10-bit addressing instead of 7-bit addressing.
+Otherwise 10-bit addressing is used only if the device address
+.I n
+is bigger than 255.
+.TP
+.BI size " nbytes"
+.br
+Set the logical size of the target device to
+.IR nbytes .
+(By default when opened, it is 256 bytes, enough for most small I2C devices.)
+IO requests will be kept within this limit.
+This value is also returned by
+.B Sys->stat
+as the length of the data file.
+.TP
+.BI subaddress " \fR[\fP n \fR]\fP"
+.br
+Cause subsequent reads and writes
+on the data file to use I2C subaddressing
+with
+.I n
+byte subaddresses (default: 1 byte).
+.I N
+must be no larger than 4.
+The target device must support subaddressing.
+By default, the device is not subaddressed.
+Setting
+.I n
+to zero switches off subaddressing.
+.PP
+When read,
+the control file displays the current settings.
+.PP
+The data file
+.BI i2c. n .data
+can be read or written to
+exchange data with the slave device with address
+.I n
+(where
+.I n
+is given in hexadecimal).
+Each write request transmits the given data
+to the device.
+Each read request sends a receive
+request to the device and returns the resulting data.
+If the I2C target is subaddressed, the current file offset
+is used as the subaddress;
+otherwise the file offset is ignored, and the device typically starts at 0 for each transfer request.
+Read and write requests are trimmed to the declared
+size of the device.
+.SH SOURCE
+.B /sys/src/9/bcm/devi2c.c
+.br
+.B /sys/src/9/bcm/i2c.c