========================================================================
                 Installing OpenBSD on a Raspberry PI 3
========================================================================

I always wanted to try out OpenBSD on bare metal. Fortunately I had an
unused Raspberry PI 3. This site is hosted on that setup. Well, it's
more bare plastic. :-)

Great help have been [3] and [4] (see "Sources" below), I suggest that
you read that, too. The following is just my notes...

Disclaimer: Some things do not work, e.g. HDMI port and wifi.

[UPDATE 2022-02-11]
wifi works since OpenBSD 6.7 [5], but I am not using it right now.
[/UPDATE]


 Pin Mapping [1]
-----------------

Before we start: Here's the GPIO Pin Mapping of the Raspberry PI 2 + 3:

+----------------------+
|                 1  2 |
|pwr              3  4 |
|                 5  6 |
|                 7  8 |
|                 9 10 |
|                11 12 |
|                 ...  |
|                39 40 |
|                      |
|                      |
|                      |
| eth      usb     usb |
+----------------------+

 1: 3.3V PWR                     2: 5V PWR
 3: GPIO 2 / I2C1 SDA            4: 5V PWR
 5: GPIO 3 / I2C1 SCL            6: GND
 7: GPIO 4                       8: UART0 TX
 9: GND                         10: UART0 RX
11: GPIO 17                     12: GPIO 18
13: GPIO 27                     14: GND
15: GPIO 22                     16: GPIO 23
17: 3.3V PWR                    18: GPIO 24
19: GPIO 10 / SPI0 MOSI         20: GND
21: GPIO 9 / SPI0 MISO          22: GPIO 25
23: GPIO 11 / SPI0 SCLK         24: GPIO 8 / SPI0 CS0
25: GND                         26: GPIO 7 / SPI0 CS1
27: Reserved                    28: Reserved
29: GPIO 5                      30: GND
31: GPIO 6                      32: GPIO 12
33: GPIO 13                     34: GND
35: GPIO 19 / SPI1 MISO         36: GPIO 16 / SPI1 CS0
37: GPIO 26                     38: GPIO 20 / SPI1 MOSI
39: GND                         40: GPIO 21 / SPI1 SCLK


 Using a USB-TTL-Serial-Converter
----------------------------------

I am using a converter by "DSD TECH" which is using a CP2102 from
"Silicon Labs" as its main chip.

My connection is as follows:
- Pin  6: red
- Pin  8: yellow
- Pin 10: orange

Be careful as the cable connected to the converter could be flipped or
use other colors. Just make sure that you connect RX to TX, TX to RX and
GND to GND. :-)


 Establish serial connection
-----------------------------

  +------ quot [3]
  |
  | the HDMI driver isn't used by the kernel [...] you need to set up
  | `cu` with a 3V serial cable, at least for initial setup.
  |
  +------ end quot


Instead of `cu` (BSD) I am using `minicom` (on GNU/Linux) to connect to
my Raspberry PI:

  +------ quot [2]
  |
  | $ minicom -b 115200 -D /dev/ttyUSB0  # your device may differ!
  |
  | Switch Flow Control Off in minicom
  | In minicom, press Ctrl + A then press Z. Now press O to configure
  | minicom.
  |
  | In the menu that appears, press the down arrow to move to Serial
  | port setup and the press then Enter key.
  |
  | Press F to switch flow control off and then press the Enter key.
  |
  | Scroll down to Exit and press Enter.
  |
  | The Raspberry PI can now be powered up. Messages from the Raspberry
  | PI will be displayed in minicom.
  |
  +------ end quot


 Installation
--------------

  +------ quot [3]
  |
  | - there's no driver for SD/MMC but that's the only thing the
  |   hardware can level-0 boot from, so you need both the uSD card and
  |   a USB disk, at least while getting started;
  | - there is no support for the built-in WiFi (a Broadcom
  |   BCM43438 SDIO 802.11), so you have to use wired Ethernet or a USB
  |   WiFi dongle [...]
  |
  +------ end quot

Installation steps are as follows, where `/dev/disk2` is the microSD
card:

  +------ quot [4]
  |
  | # dd if=miniroot63.fs of=/dev/disk2 bs=1m
  |
  | # mount /dev/disk2/boot /somewhere
  |
  | # echo "program_usb_boot_mode=1" >> /somewhere/BOOT/config.txt
  |
  +------ end quot

Put the microSD card and a USB stick into the Raspberry PI. Start
`minicom` as mentioned above. Boot the Raspberry PI by empowering it.
Follow installation instructions. After installation you should be able
to use the Raspberry PI without the microSD card and with only the USB
stick connected.


 Sources
---------

[1] https://docs.microsoft.com/en-us/windows/iot-core/learn-about-hardware/pinmappings/pinmappingsrpi -- 2020-04-27
[2] https://startingelectronics.org/articles/raspberry-PI/serial-port-connecting-linux/ -- 2020-04-27
[3] https://undeadly.org/cgi?action=article&sid=20170409123528 -- 2020-04-27
[4] https://www.tumfatig.net/20180706/running-openbsd-on-raspberry-pi-3/ -- 2020-04-27
[5] https://www.openbsd.org/plus67.html -- 2022-02-11


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 Changelog
-----------

2020-05-10   creation
2022-02-11   edited to add: wifi works