# Temp. and Humidity Logger for the RPI4b

This is a simple temperature and humidity logger for a Raspberry Pi 4B running
FreeBSD 14. It is capable of taking temperature and humidity every 5
seconds and storing them into a database. The measurements can then be viewed
using either the integrated display, or, they can be exported to a USB drive.

# Contents
1. [Construction](#construction)
2. [OS Preparation](#os-preparation)
3. [Installation](#installation)
4. [Configuration](#configuration)
5. [Usage](#usage)

# Construction
The following is a general list of materials required:

- 1x Raspberry Pi 4 Model B [^1]
- 1x Breadboard (medium or large)
- 4x Push button
- 1x DHT11/DHT22 [^2]
- 1x DS3231 (or other RTC)
- 1x 16x2 HD44780U based LCD (such as a 1602 LCD)
- 1x N-channel MOSFET (optional, for turning off the screen)
- 1x Schottky diode (optional, for turning off the screen)
- 1x 1kΩ resistor [^3]
- 2x 10kΩ potentiometers (optional, for display brightness and contrast control)

[^1]: Other versions and models will very likely work (such as the Pi 3B), the
wiring will just need to be adjusted.

[^2]: Any temperature and humidity sensor for which a FreeBSD kernel module
exists will work. You can even use separate sensors for each!

[^3]: If your DHT11/DHT22 is mounted on a carrier board with only three
terminals, it likely already has this resistor. When in doubt, check the 
data sheet.

The following is one possible way to assemble the device. It should be noted,
however, that all of the pins are configurable. Thus, the following design
should be modified depending on the exact make and model of the parts being
used.

![Breadboard diagram of a circuit.](misc/circut_bb.svg)

If an I²C device will be used (such as the DS3231 or an I²C sensor), care must
be taken that the data lines are connected to GPIO pins 2 and 3 (physical pins 3
and 5). If they are not, the configuration files provided in this repository
will need to be updated to reflect the new I²C bus location. If multiple I²C
devices are used, multiple busses will need to be created. For more information
about I²C on FreeBSD see the following man pages: [iic(4)][1], [iicbus(4)][2],
and [fdt(4)][3].

[1]: https://man.freebsd.org/cgi/man.cgi?query=iic&apropos=0&sektion=4&manpath=FreeBSD+14.0-RELEASE+and+Ports
[2]: https://man.freebsd.org/cgi/man.cgi?query=iicbus&apropos=0&sektion=4&manpath=FreeBSD+14.0-RELEASE+and+Ports
[3]: https://man.freebsd.org/cgi/man.cgi?query=fdt&apropos=0&sektion=4&manpath=FreeBSD+14.0-RELEASE+and+Ports

Some images of a fully assembled and working unit follow (using different GPIO
pins than above):

![A finished build](misc/finished1.jpg)

![A finished build](misc/finished2.jpg)

# OS Preparation

This software was designed and tested on a system running FreeBSD 14.0. However,
it should work on systems running FreeBSD 13 as well as on systems running
future versions of FreeBSD. The FreeBSD installation process is very well
documented in [The FreeBSD Handbook][4]. For convinience, the general procedure
is also provided below. If any issues arise or you have any questions, be
consult the handbook.

[4]: https://docs.freebsd.org/en/books/handbook/

First, download the latest image for the Raspberry Pi [here][5]. It is also a
good idea to pick up the checksum file. Once done you should have two files with
names similar to `FreeBSD-14.0-RELEASE-arm64-aarch64-RPI.img.xz` and
`CHECKSUM.SHA256-FreeBSD-14.0-RELEASE-arm64-aarch64-RPI`. To verify the
downloaded files, open a terminal and execute the following commands (use sha512
if you downloaded the sha512 checksum file):

[5]: https://www.freebsd.org/where/

- GNU/Linux and FreeBSD:
  ```sh
  sha256sum -c CHECKSUM.SHA256-FreeBSD-14.0-RELEASE-arm64-aarch64-RPI
  ```
- OpenBSD:
  ```sh
  sha256 -c CHECKSUM.SHA256-FreeBSD-14.0-RELEASE-arm64-aarch64-RPI
  ```

For other operating systems, please consult the relevant documentation.

Because device numbering is not persistent across boots, the export feature of
this software does not allow a specific device to be excluded from the
list. This may in the feature be rectified by an update, but for now, it is
recommend to install the OS to a microSD card. Most Raspberry Pis come with a
small USB device that can be used to write to microSD cards, as well as the
microSD card itself. If not, you can find both online very cheaply. Once you
have connected your device find it's device file using a tool like `fdisk` or
`geom`. Then execute the following commands as root to write the image to the
microSD card:

```sh
unxz FreeBSD-14.0-RELEASE-arm64-aarch64-RPI.img.xz
cp FreeBSD-14.0-RELEASE-arm64-aarch64-RPI.img /path/to/device
sync
```

If you are not comfortable with performing this operation on the terminal,
another option is to use software such as [balenaEtcher][6].

[6]: https://etcher.balena.io/

Once this process is done (which may take a while), insert the microSD card into
the Raspberry Pi, attach a keyboard and monitor, and plug the Pi in to turn it
on.

# Installation

Once the system has booted and you see the login prompt, enter `root` as the
username and leave the password blank. You should now see a shell prompt. The first
thing to do is to configure the temperature sensor and the RTC. To do the
former, *append* the following to the end of the `/boot/loader.conf` file:

```conf
# Load the DHT11/DHT22 kernel module
gpioths_load="YES"
# The GPIO bus that manages the pins that the sensor is connected to
hint.gpioths.0.at=gpiobus0
# This number should have only the bit set for the position corresponding to the
# GPIO pin number that the sensor is connected to. For example:
# 2097152 -> 1000000000000000000000 -> pin 21 (bit 22)
# 1 -> 1 -> pin 0 (bit 1)
# 2 -> 10 -> pin 1 (bit 2)
hint.gpioths.0.pins=2097152

# Load the DS3231 kernel module
ds3231_load="YES"
# The I2C bus the controls the pins the sensor is connected to
hint.ds3231.0.at=iicbus0
# The *8 BIT* address of the sensor. The following is the default for a DS3131
# addr = 0xd0
hint.ds3231.0.addr=208
```

The FreeBSD base system comes with the text editor `vi`. For information about
how to use it, execute `man vi` or see [vi(1)][7].

[7]: https://man.freebsd.org/cgi/man.cgi?query=vi&manpath=FreeBSD+14.0-RELEASE+and+Ports

The next step is to enable I²C for the DS3131. Once again, *append* the
following to the end of the `[all]` section of the `/boot/msdos/config.txt`
file:

```conf
# Set the initial state of pins GPIO 2 and 3. Change this if you use different pins.
gpio=2,3=a0
# Load the overlay for an the DS3231 I2C real-time clock
dtoverlay=i2c-rtc,ds3231
```

For example, the `/boot/msdos/config.txt` file on my Raspberry Pi 4B looks like
this:

```conf
[all]
arm_64bit=1
dtparam=audio=on,i2c_arm=on,spi=on
dtoverlay=mmc
dtoverlay=disable-bt
device_tree_address=0x4000
kernel=u-boot.bin
gpio=2,3=a0
dtoverlay=i2c-rtc,ds3231

[pi4]
hdmi_safe=1
armstub=armstub8-gic.bin
enable_uart=1
```

Then enable the `ntpd` and `ntpdate` services to sync with the RTC on boot and
periodically:

```sh
service ntpd enable
service ntpdate enable
```

If you want, you can also change the `root` password at this point:

```sh
passwd
```

After doing this, reboot the system. Once done, execute the following commands:

```sh
sysctl dev.ds3231.0.temperature dev.gpioths.0.temperature
```

If you get a warning about an unknown oid, it means that the sensor is not
installed or configured correctly.

It should be noted that FreeBSD does not currently support wireless on the
Raspberry Pi 4 at the time of writing. Thus, you will need to use a wired
connection (or consult the [handbook][4] for information about other ways to get
packages).

Once the sensors are detected and we have internet, we can install the
dependencies for this software. Execute the following command to bootstrap the
binary package manager [pkg(7)][8] and install sqlite3 and curl.

[8]: https://man.freebsd.org/cgi/man.cgi?query=pkg&manpath=FreeBSD+14.0-RELEASE+and+Ports

```sh
pkg install sqlite3 curl
```

When prompted to install `pkg`, type `y` and then press enter.

We can now download the source of this software:

```sh
cd /tmp
curl -O "https://git.zander.im/Zander671/rpi4b-temp-humidity/archive/main.tar.gz"
tar xf main.tar.gz
cd rpi4b-temp-humidity
```

At this point, take a moment to edit the `config.mk` file to to change any
default options. These can also be changed after installation by editing
`/usr/local/etc/rpi4b-temp-humidity/config.conf`.

Once you have configured everything to your liking, execute the following
commands to build and install the software.

```sh
make all install
```

# Configuration

The final step is to configure the software via the
`/usr/local/etc/rpi4b-temp-humidity/config.conf` file. Once you have done this
to your liking, execute the following command to enable the software on boot:

```sh
# Optional, set an alternate config file path
sysrc rpi4b-temp-humidity_config_file="/path/to/your/config/file"
service rpi4b-temp-humidity enable
```

# Usage

The following command line flags are supported:

- `-h`: print a simple help message, then exit
- `-v`: enable more verbose output
- `-s`: exit immediately if an error is found in the config file
- `-f`: specify a different config file path

These can also be modified via the following [rc.conf(5)][9] variables (or via
the [sysrc(8)][10] command).

- `rpi4b-temp-humidity_config_file`: same as `-f`
- `rpi4b-temp-humidity_strict_config`: same as `-s`

[9]: https://man.freebsd.org/cgi/man.cgi?query=rc.conf&manpath=FreeBSD+14.0-RELEASE+and+Ports
[10]: https://man.freebsd.org/cgi/man.cgi?query=sysrc&manpath=FreeBSD+14.0-RELEASE+and+Ports