Module: UART

Defined in:
lib/uart.rb

Constant Summary collapse

VERSION = 
'1.0.0'

Class Method Summary collapse

Class Method Details

.data_bits(t, val) ⇒ Object 



67
68
69
70
71
 
# File 'lib/uart.rb', line 67

def data_bits t, val
  t.cflag &= ~Termios::CSIZE               # clear previous values
  t.cflag |= Termios.const_get("CS#{val}") # Set the data bits
  t
end

.open(filename, speed = 9600, mode = '8N1') ⇒ Object

Open a UART as a file.

For example, we have a serial connection on ‘/dev/tty.usbserial-00000000’. It’s speed is 9600, 8 data bits, 1 stop bit, and no parity:

serial = UART.open '/dev/tty.usbserial-00000000', 9600, '8N1'
serial.write 'whatever'

A speed of 9600, 8 data bits, no parity, and 1 stop bit is default, so we can reduce the code to this:

serial = UART.open '/dev/tty.usbserial-00000000'
serial.write 'whatever'

Finally, we can give a block and the file will be automatically closed for us like this:

UART.open '/dev/tty.usbserial-00000000' do |serial|
  serial.write 'whatever'
end



28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
 
# File 'lib/uart.rb', line 28

def open filename, speed = 9600, mode = '8N1'
  f = File.open filename, File::RDWR|Fcntl::O_NOCTTY|Fcntl::O_NDELAY
  f.binmode
  f.sync = true

  # enable blocking reads, otherwise read timeout won't work
  f.fcntl Fcntl::F_SETFL, f.fcntl(Fcntl::F_GETFL, 0) & ~Fcntl::O_NONBLOCK

  t = Termios.tcgetattr f
  t.iflag = 0
  t.oflag = 0
  t.lflag = 0

  if mode =~ /^(\d)(\w)(\d)$/
    t = data_bits    t, $1.to_i
    t = stop_bits    t, $3.to_i
    t = parity       t, { 'N' => :none, 'E' => :even, 'O' => :odd }[$2]
    t = speed        t, speed
    t = read_timeout t, 5
    t = reading      t
  else
    raise ArgumentError, "Invalid format for mode"
  end

  Termios.tcsetattr f, Termios::TCSANOW, t
  Termios.tcflush f, Termios::TCIOFLUSH

  if block_given?
    begin
      yield f
    ensure
      f.close
    end
  else
    f
  end
end

.parity(t, val) ⇒ Object 



85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
 
# File 'lib/uart.rb', line 85

def parity t, val
  case val
  when :none
    t.cflag &= ~Termios::PARENB
  when :even
    t.cflag |= Termios::PARENB  # Enable parity
    t.cflag &= ~Termios::PARODD # Make it not odd
  when :odd
    t.cflag |= Termios::PARENB  # Enable parity
    t.cflag |= Termios::PARODD  # Make it odd
  else
    raise
  end
  t
end

.read_timeout(t, val) ⇒ Object 



109
110
111
112
113
 
# File 'lib/uart.rb', line 109

def read_timeout t, val
  t.cc[Termios::VTIME] = val
  t.cc[Termios::VMIN] = 0
  t
end

.reading(t) ⇒ Object 



116
117
118
119
 
# File 'lib/uart.rb', line 116

def reading t
  t.cflag |= Termios::CLOCAL | Termios::CREAD
  t
end

.speed(t, speed) ⇒ Object 



102
103
104
105
106
 
# File 'lib/uart.rb', line 102

def speed t, speed
  t.ispeed = Termios.const_get("B#{speed}")
  t.ospeed = Termios.const_get("B#{speed}")
  t
end

.stop_bits(t, val) ⇒ Object 



74
75
76
77
78
79
80
81
82
 
# File 'lib/uart.rb', line 74

def stop_bits t, val
  case val
  when 1 then t.cflag &= ~Termios::CSTOPB
  when 2 then t.cflag |= Termios::CSTOPB
  else
    raise
  end
  t
end