Class: Denko::AnalogIO::ADS1100

Inherits:
Object
  • Object
show all
Includes:
InputHelper, Behaviors::Lifecycle, Behaviors::Poller, I2C::Peripheral
Defined in:
lib/denko/analog_io/ads1100.rb

Constant Summary collapse

I2C_ADDRESS = 
0x48
I2C_FREQUENCY = 
400_000
SAMPLE_RATES =

Convert sample rates in samples-per-seconds to their bit representation.

[  # Bitmask
  128,            # 0b00
  32,             # 0b01
  16,             # 0b10
  8               # 0b11 (default)
]
BIT_RANGES =

Faster sampling rates have lower resolution.

[    # Bitmask   Bits  SPS
  4_096,          # 0b00      12    128
  16_383,         # 0b01      14    32
  32_767,         # 0b10      15    16
  65_535,         # 0b11      16    8
]
WAIT_TIMES =

Wait times need to be slightly longer than the actual sample times.

SAMPLE_RATES.map { |rate| (1 / rate.to_f) + 0.0005 }
GAINS =

Bitmask Full scale voltage

[  # Bitmask   Full scale voltage
  1,       # 0b00      Vdd
  2,       # 0b01      Vdd / 2
  4,       # 0b10      Vdd / 4
  8,       # 0b11      Vdd / 8
]
CONFIG_STARTUP =

Default config register:

Bit 7   : Start conversion (write 1) | Conversion in progress (read 1)
Bit 6-5 : Reserved, must be 00
Bit 4   : Conversion mode. 0 = continuous (datasheet default). 1 = single (our default).
Bit 3-2 : Sample Rate (see array above)
Bit 1-2 : PGA setting (see array above)

0b00011100
GAIN_CLEAR =

Masks

0b11111100
SAMPLE_RATE_CLEAR = 
0b11110011

Constants included from Behaviors::Reader

Behaviors::Reader::READ_WAIT_TIME

Constants included from Behaviors::Lifecycle

Behaviors::Lifecycle::CALLBACK_METHODS

Constants included from I2C::Peripheral

I2C::Peripheral::I2C_REPEATED_START

Instance Attribute Summary collapse

Attributes included from InputHelper

#smoothing, #smoothing_size

Attributes included from Behaviors::Threaded

#interrupts_enabled, #thread

Attributes included from Behaviors::State

#state

Attributes included from I2C::Peripheral

#i2c_frequency, #i2c_repeated_start

Attributes included from Behaviors::Component

#board, #params

Instance Method Summary collapse

Methods included from InputHelper

#on_change, #smooth_input, #smoothing_set

Methods included from Behaviors::Poller

#poll, #poll_using, #stop

Methods included from Behaviors::Threaded

#enable_interrupts, included, #mruby_thread_check, #stop, #stop_thread, #threaded, #threaded_loop

Methods included from Behaviors::Reader

#read, #read_busy?, #read_nb, #read_raw, #read_using, #update

Methods included from Behaviors::Callbacks

#add_callback, #callbacks, #remove_callback, #update

Methods included from Behaviors::State

#update_state

Methods included from Behaviors::Lifecycle

included

Methods included from I2C::Peripheral

#address, #i2c_default, #i2c_read, #i2c_read_raw, #i2c_write

Methods included from Behaviors::BusPeripheralAddressed

#address

Methods included from Behaviors::BusPeripheral

#atomically

Methods included from Behaviors::Component

#initialize, #micro_delay

Instance Attribute Details

#sample_rate_mask ⇒ Object 



92
93
94
 
# File 'lib/denko/analog_io/ads1100.rb', line 92

def sample_rate_mask
  @sample_rate_mask ||= SAMPLE_RATES.index(sample_rate)
end

Instance Method Details

#_read ⇒ Object 



58
59
60
61
62
63
64
65
66
67
 
# File 'lib/denko/analog_io/ads1100.rb', line 58

def _read
  # Set bit 7 of the config register and write it to start conversion.
  i2c_write(config_register | (1<<7))

  # Sleep the right amount of time for conversion, based on sample rate bits.
  sleep WAIT_TIMES[sample_rate_mask]

  # Read the result, triggering callbacks.
  i2c_read(2)
end

#config_register ⇒ Object

Default to single conversion.



81
82
83
 
# File 'lib/denko/analog_io/ads1100.rb', line 81

def config_register
  @config_register ||= CONFIG_STARTUP
end

#full_scale_voltage ⇒ Object

Unlike some ADS parts, full-scale voltage depends on supply (Vdd). User must specify.



118
119
120
 
# File 'lib/denko/analog_io/ads1100.rb', line 118

def full_scale_voltage
  @full_scale_voltage ||= params[:full_scale_voltage]
end

#gain ⇒ Object 



113
114
115
 
# File 'lib/denko/analog_io/ads1100.rb', line 113

def gain
  @gain ||= params[:gain] || 1
end

#gain=(gain) ⇒ Object 



102
103
104
105
106
107
 
# File 'lib/denko/analog_io/ads1100.rb', line 102

def gain=(gain)
  raise ArgumentError "wrong gain: #{gain.inspect} given for ADS1100" unless GAINS.include?(gain)
  @gain_mask = GAINS.index(gain)
  config_register = (config_register & GAIN_CLEAR) | gain_mask
  @gain      = gain
end

#gain_mask ⇒ Object 



109
110
111
 
# File 'lib/denko/analog_io/ads1100.rb', line 109

def gain_mask
  @gain_mask ||= GAINS.index(gain)
end

#listen(pin, divider = nil) ⇒ Object

Raises:

  • (StandardError) 


69
70
71
 
# File 'lib/denko/analog_io/ads1100.rb', line 69

def listen(pin, divider=nil)
  raise StandardError, "ADS1100 does not implement #listen. Use #read or #poll instead"
end

#pre_callback_filter(bytes) ⇒ Object 



73
74
75
76
77
78
 
# File 'lib/denko/analog_io/ads1100.rb', line 73

def pre_callback_filter(bytes)
  # Readings are 16-bits, signed, big-endian.
  value = bytes.pack("C*").unpack("s>")[0]
  # Let InputHelper module handle smooothing.
  super(value)
end

#sample_rate ⇒ Object 



96
97
98
 
# File 'lib/denko/analog_io/ads1100.rb', line 96

def sample_rate
  @sample_rate ||= params[:sample_rate] || 8
end

#sample_rate=(rate) ⇒ Object 



85
86
87
88
89
90
 
# File 'lib/denko/analog_io/ads1100.rb', line 85

def sample_rate=(rate)
  raise Argument Error "wrong sample_rate: #{sample_rate.inspect} given for ADS1100" unless SAMPLE_RATES.include?(rate)
  @sample_rate_mask = SAMPLE_RATES.index(rate)
  config_register = (config_register & SAMPLE_RATE_CLEAR) | (sample_rate_mask << 2)
  @sample_rate = rate
end

#volts_per_bit ⇒ Object 



122
123
124
 
# File 'lib/denko/analog_io/ads1100.rb', line 122

def volts_per_bit
  full_scale_voltage / (GAINS[gain_mask] * BIT_RANGES[sample_rate_mask]).to_f
end