baud

# Baud

## Platform detection

`uname` returns Linux, Darwin, and MSYS_NT-6.1
in Linux, Mac and Windows 7 (both 32 and 64 bits) respectively

`:os.type()` returns:

  - `{:unix, :darwin}` in MacPro OS X El Capitan
  - `{:unix, :linux}` in Ubuntu 16.04 64x (OTP from ubuntu repos)
  - `{:unix, :linux}` in Ubuntu 16.04 32x (OTP from ubuntu repos)
  - `{:win32, :nt}` in Windows 7 32x con OTP 32x
  - `{:win32, :nt}` in Windows 7 64x con OTP 64x

## Windows setup

Install Elixir
```bash
#Web installer asks to download and install the OTP if not found
https://repo.hex.pm/elixir-websetup.exe
```

Install MSYS2
```bash
#Install msys2-{x86_64,i686}-20160205.exe from https://msys2.github.io/
#Default installation folder is C:\msys{32,64}
#Install gcc and make from the msys2 console:
pacman -S mingw-w64-{x86_64,i686}-gcc
pacman -S make
#Add C:\msys{32,64}\mingw{32,64}\bin to PATH (turn gcc visible)
#Add C:\msys{32,64}\usr\bin to PATH (turn make and other utils visible)
#Notice that 64 bit systems use x86_64 and 32 bit systems use i686
```
With the *PATH* exports above `mix` can run both form *cmd* and from *msys2 console*.
Running from *cmd* triggers the **Windows application crash report dialog** when the native port crashes.

## MAC setup
**Expect machine crashes due to serial drivers.**

Install Elixir
```bash
brew install elixir
mix deps.get
mix test
```
Join the wheel group
```bash
sudo dscl . append /Groups/wheel GroupMembership samuel
```

## Ubuntu 16 setup

Install Elixir
```bash
wget https://packages.erlang-solutions.com/erlang-solutions_1.0_all.deb
sudo dpkg -i erlang-solutions_1.0_all.deb
sudo apt-get install elixir
mix deps.get
mix test
```

Join the dialout group
```bash
sudo gpasswd -a samuel dialout
```

## Testing

- See `test/test_helper.exs` for requirements. Port names are hardcoded.
- Use dual FTDI USB-Serial adapter ICUSB2322F with 3 wire null modem between them.

## Miscellaneous

A pairs of devices are created:
  - `tty` requires DCD line raised or open blocks.
  Putting in the red null modem adapter makes baud work.
  - `cu` does not require DCD line raised
  - http://pbxbook.com/other/mac-tty.html

Port names:
- `FTDI` FT232R /dev/tty.usbserial-FTYHQD9MA | /dev/tty.usbserial-FTYHQD9MB | ...
  - Ports wont reappear if unplugged while open
- `Prolific` PL2303 /dev/tty.usbserial | /dev/tty.usbserial2 | ...
  - Ports detected only on first plug, reboot required to have them back if unplugged
  - Changes second port postfix number on replug
- `Silab` CP210x /dev/tty.SLAB_USBtoUART | ***????***

Latency and Packetization:
- Posix minimum kernel packetization is 100ms because VTIME is measured in 0.1s units.
- Win32 kernel packetizacion granularity is in millis but have not tested it yet
- The USB-Serial converters have their own packetization delays (see links below)
- https://projectgus.com/2011/10/notes-on-ftdi-latency-with-arduino/
- http://www.unixwiz.net/techtips/termios-vmin-vtime.html
- http://www.lookrs232.com/com_port_programming/api_timeout.htm

Flushing and O_SYNC:
- Not using O_SYNC flag neither explicitly flushing the handles
- http://dreamlayers.blogspot.mx/2011/10/unix-serial-port-output-buffer.html