owc4

Usage

Overview

The owc module implements Dallas Semiconductor 1-Wire signaling. It attaches the ow(4) driver 1-Wire bus protocol. The owc device implements the Link Layer of the 1-Wire bus protocol stack.

Bit banging a pin on a gpiobus(4) is the only supported controller. Both standard and overdrive transfer timings are implemented. Strong pull-up functionality needed to support parasitic mode is not implemented.

To enable 1-Wire for FDT systems requires modifying the DTS for your board to add something like:

/ {
	...
	onewire {
		compatible = "w1-gpio";
		gpios = <&gpio 4 1>;
	};
	...
};

The gpios property describes the GPIO pin the 1-Wire bus is connected to. For more details about the gpios property, please consult /usr/src/sys/dts/bindings-gpio.txt.

On a device.hints(5) based system these values are required for the owc:

hint.owc.%d.at

The gpiobus you are attaching to.

hint.owc.%d.pins

This is a bitmask that defines a pin on the gpiobus that is to be used for the 1-Wire bus. For instance, to configure pin 10, use the bitmask of 0x400. Please note that this mask should have only one bit set (any other bits - i.e., pins - will be ignored).

Legal

1-Wire is a registered trademark of Maxim Integrated Products, Inc.

Caveats

The gpio driver implements timing by busy waiting, which can cause a high load on slower systems.