NAME

gpioiic — GPIO I2C controller

SYNOPSIS

gpioiic* at gpio? offset 0 mask 0x3 flag 0x0
gpioiic* at gpio?
iic* at gpioiic?

DESCRIPTION

The gpioiic driver allows bit-banging an I2C bus as a master using two GPIO pins. By default the first pin is used as a serial data (SDA) signal and the second as a serial clock (SCL). If the flag locator is set to 0x01, the order of the SDA and SCL signals is reversed. Both GPIO pins must be able to drive an output and the SDA pin must be also able to read an input.

The pins can be specified in the kernel configuration with the offset and the mask locators. The offset and mask can also be specified when gpioiic is attached at runtime using the GPIOATTACH ioctl(2) on the gpio(4) device. Each bit in the mask locator defines one pin; the pin number is calculated as an addition of the bit position and the offset locator. For example, offset 17 and mask 0x5 defines pin numbers 17 and 19.

SEE ALSO

gpio(4), iic(4), intro(4)

HISTORY

The gpioiic driver first appeared in OpenBSD 3.9 and NetBSD 5.0.

AUTHORS

The gpioiic driver was written by Alexander Yurchenko <grange@openbsd.org> and was ported to NetBSD by Marc Balmer <marc@msys.ch>.

CAVEATS

A gpioiic device can not be detached from the gpio(4) bus at runtime due to the fact that iic(4) busses can not detach once attached.