BH1750 Ambient Light Sensor kernel driver for FreeBSD

About

There is a FreeBSD kernel driver for a bh1750 sensor. It force the sensor to measure abmient light every 5 seconds and update a corresponding sysctl branch.

Installation

You need a FreeBSD kernel source codes.

% make depend
% make
% sudo make install

You may need to edit fdt-overlay sources for Your needs, make and install them:

% cd fdt-overlay
% make
% sudo make install

Append an overlay to "/boot/loader.conf" and reboot:

fdt_overlays="sun8i-h3-sid,sun8i-h3-ths,sun8i-h3-bh1750-i2c0"

Now You can load the module and check its work:

% kldload bh1750
% sysctl dev.bh1750.0

Description

The driver allows you to set device measurement parameters via sysctl variables (and fdt-overlay parameters) and obtain result and calculated parameters from the driver. You can set and get the following parameters of the device:

• measurement mode to H-resolution or H-resolution2, which changes the measurment sensitivity by 2 times;
• MTReg value, which leads to recalculation of the actual sensitivity and, accordingly, a result ready time;
• percentage of reduced quality of the chip from the ideal one, which will lead to a proportional increase of a result ready time. The manufacturer allows a decrease in quality of chips up to 50%. You may need it if You suspect that Your specimen is unable to complete the measurement on time;
• polling time up to 255 seconds (through fdt-overlay parameter only by now. I still think if it may needed to dynamically change it);
• get raw data from the chip as so called "counts";
• get calculated illuminance value in mlx.

% sysctl dev.bh1750.0
dev.bh1750.0.ready-time: 441960
dev.bh1750.0.hres-mode: 2
dev.bh1750.0.quality-lack: 0
dev.bh1750.0.mtreg: 254
dev.bh1750.0.illuminance: 5772
dev.bh1750.0.sensitivity: 113
dev.bh1750.0.polling-time: 2
dev.bh1750.0.counts: 51
dev.bh1750.0.connected: 1
dev.bh1750.0.%parent: iicbus0
dev.bh1750.0.%pnpinfo: name=bh1750@23 compat=bh1750
dev.bh1750.0.%location: addr=0x46
dev.bh1750.0.%driver: bh1750
dev.bh1750.0.%desc: BH1750 Ambient Light Sensor module
dev.bh1750.%parent: 

Status

The driver has been tested on "Raspberry Pi 2", "Orange Pi PC" and "Orange Pi Zero" (sun8i-h2-plus-i2c0.dtbo is also needed).

Added cdev support for devices.

Added support of poll(2) and kevent(2) to user processes.

Re-confirmation required:

• During testing, two sensors with addresses 0x23 and 0x5С were used simultaneously.