ads1256 Namespace Reference

Functions
	output_json ()
	parse_args (raw_args)
	rdata ()
	read_fsc_reg ()
	read_ofc_reg ()
	rreg (register)
	selfcal ()
	sync ()
	twos_complement_to_integer_24bit (twos_complement)
	wakeup ()
	wreg (register, data)
	write_adcon_reg ()
	write_drate_reg ()
	write_mux_reg ()
	write_status_reg ()

Variables
int	cs = 22
int	drdy = 17
	max_speed_hz
str	mode = 'analog'
int	output = -1
	register_address
	register_data
	spi = spidev.SpiDev()

Function Documentation

output_json()

ads1256.output_json

(

)

Prints a JSON of the register_data for development and testing.

Definition at line 147 of file ads1256.py.

def output_json():
    """Prints a JSON of the register_data for development and testing."""
    print(json.dumps(register_data, sort_keys=True, indent=4))
 
 

parse_args()

ads1256.parse_args

(

raw_args

)

Parses the args into ready to write register_data.

Definition at line 152 of file ads1256.py.

def parse_args(raw_args):
    """Parses the args into ready to write register_data."""
    # First parse the CLI.
    parser = argparse.ArgumentParser()
    parser.add_argument("--mode", type=str, default="analog",
            help="Mode: analog, calibrationFSC, calibrationOFC, digitalIn, digitalOut default analog")
    parser.add_argument("--port_p", type=str, default="0",
            help="Positive Analog Input Port: 0 thru 8 default 0")
    parser.add_argument("--port_n", type=str, default="8",
            help="Negative Analog Input Port: 0 thru 8 default 8 (AINCOM)")
    parser.add_argument("--gain", type=str, default="1",
            help="Input Amp Gain: 1, 2, 4, 8, 16, 32, 64 default 1")
    parser.add_argument("--rate", type=str, default="2.5",
            help="Data Rate in samples per second: 2.5, 5, 10, 15, 25, 30, 50, 60, 100, 500, 1000, 2000, 3750, 7500, 15000, 30000 default 2.5")
    parser.add_argument("--buffer", type=str, default="off",
            help="Input Buffer: off, on default off")
    parser.add_argument("--sdcs", type=str, default="off",
            help="SDCS sensor direct current source microamps: off, 0.5, 2, 10 default off")
    parser.add_argument("--pin", type=str, default="D0",
            help="Specify pin for modes digitalIn and digitalOut: D0, D1, D2, D3 default D0")
    parser.add_argument("--output", type=str, default="-1",
            help="Absence means input mode, or specify output for modes digitalIn and digitalOut: 0, 1 default input mode")
    parser.add_argument("-t", "--test", action="store_true",
            help="Print JSON of register_data")
    args = parser.parse_args(raw_args)
 
    # Save global configs
    global mode
    mode = args.mode
    global output
    output = args.output
 
    # Process the STATUS register, including the BUFEN analog input buffer property.
    register_data['status'] = 0x00
    if (args.buffer == 'on'):
        register_data['status'] = 0x02
    if (args.buffer == 'off'):
        register_data['status'] = 0x00
 
    # Process the ADCON register, including PGA gain and SDCS property.
    register_data['adcon'] = 0x20  # Default clock out rate setting
    if (args.gain == '1'):
        register_data['adcon'] += 0x00
    if (args.gain == '2'):
        register_data['adcon'] += 0x01
    if (args.gain == '4'):
        register_data['adcon'] += 0x02
    if (args.gain == '8'):
        register_data['adcon'] += 0x03
    if (args.gain == '16'):
        register_data['adcon'] += 0x04
    if (args.gain == '32'):
        register_data['adcon'] += 0x05
    if (args.gain == '64'):
        register_data['adcon'] += 0x06
    if (args.sdcs == 'off'):
        register_data['adcon'] += 0x00
    if (args.sdcs == '0.5'):
        register_data['adcon'] += 0x08
    if (args.sdcs == '2'):
        register_data['adcon'] += 0x10
    if (args.sdcs == '10'):
        register_data['adcon'] += 0x18
 
    # Process the DRATE register, including the rate property.
    register_data['drate'] = 0x03
    if (args.rate == '30000'):
        register_data['drate'] = 0xF0
    if (args.rate == '15000'):
        register_data['drate'] = 0xE0
    if (args.rate == '7500'):
        register_data['drate'] = 0xD0
    if (args.rate == '3750'):
        register_data['drate'] = 0xC0
    if (args.rate == '2000'):
        register_data['drate'] = 0xB0
    if (args.rate == '1000'):
        register_data['drate'] = 0xA1
    if (args.rate == '500'):
        register_data['drate'] = 0x92
    if (args.rate == '100'):
        register_data['drate'] = 0x82
    if (args.rate == '60'):
        register_data['drate'] = 0x72
    if (args.rate == '50'):
        register_data['drate'] = 0x63
    if (args.rate == '30'):
        register_data['drate'] = 0x53
    if (args.rate == '25'):
        register_data['drate'] = 0x43
    if (args.rate == '15'):
        register_data['drate'] = 0x33
    if (args.rate == '10'):
        register_data['drate'] = 0x23
    if (args.rate == '5'):
        register_data['drate'] = 0x13
    if (args.rate == '2.5'):
        register_data['drate'] = 0x03
 
    # Process the MUX register, including the port.
    # register_data['mux'] = 0x08
    register_data['mux'] = (int(args.port_p) << 4) | int(args.port_n)
 
    # Process the gpio_direction_bitmask and gpio_status_bitmask registers, including the pin property.
    register_data['gpio_direction_bitmask'] = 0x10
    register_data['gpio_status_bitmask'] = 0x01
    if (args.pin == 'D0'):
        register_data['gpio_direction_bitmask'] = 0x10
        register_data['gpio_status_bitmask'] = 0x01
    if (args.pin == 'D1'):
        register_data['gpio_direction_bitmask'] = 0x20
        register_data['gpio_status_bitmask'] = 0x02
    if (args.pin == 'D2'):
        register_data['gpio_direction_bitmask'] = 0x40
        register_data['gpio_status_bitmask'] = 0x04
    if (args.pin == 'D3'):
        register_data['gpio_direction_bitmask'] = 0x80
        register_data['gpio_status_bitmask'] = 0x08
 
    # Optionally output register state for development purposes.
    if args.test:
        output_json()
        exit()
 
 
# Functions that read or write to the device.
# Device commands are run by functions named after the datasheet provided device command names.
# The datasheet names are all caps, Python names are lowercase, other than that issue, they match.
# The complete list of commands is on datasheet page 34 table 24.
 
 

rdata()

ads1256.rdata

(

)

Run RDATA command as explained on datasheet page 34.

Definition at line 313 of file ads1256.py.

def rdata():
    """Run RDATA command as explained on datasheet page 34."""
    while True:
        if (GPIO.input(drdy) == 0):
            break
    GPIO.output(cs, 0)
    spi.writebytes([0x01])
    buf = spi.readbytes(3)
    GPIO.output(cs, 1)
    read = (buf[0] << 16) & 0xff0000
    read |= (buf[1] << 8) & 0xff00
    read |= (buf[2]) & 0xff
    return twos_complement_to_integer_24bit(read)
 
 

read_fsc_reg()

ads1256.read_fsc_reg

(

)

Read the FSC calibration value.

Definition at line 342 of file ads1256.py.

def read_fsc_reg():
    """Read the FSC calibration value."""
    # See datasheet page 33 to read the raw byte values.
    # FSC per datasheet pg 24 is an unsigned 24 bit integer.
    register_data['fsc'] = 0x000000
    register_data['fsc'] += (rreg(register_address['fsc2']) << 16)
    register_data['fsc'] += (rreg(register_address['fsc1']) << 8)
    register_data['fsc'] += rreg(register_address['fsc0'])
 
 

read_ofc_reg()

ads1256.read_ofc_reg

(

)

Read the OFC calibration value.

Definition at line 352 of file ads1256.py.

def read_ofc_reg():
    """Read the OFC calibration value."""
    # See datasheet page 33 to read the raw byte values.
    # OFC per datasheet pg 24 is a twos complement 24 bit signed integer.
    ofc_twos_complement = 0x000000
    ofc_twos_complement += (rreg(register_address['ofc2']) << 16)
    ofc_twos_complement += (rreg(register_address['ofc1']) << 8)
    ofc_twos_complement += rreg(register_address['ofc0'])
    register_data['ofc'] = twos_complement_to_integer_24bit(ofc_twos_complement)
 
 

rreg()

ads1256.rreg

(

register

)

Run RREG command as explained on datasheet page 36.

Definition at line 283 of file ads1256.py.

def rreg(register):
    """Run RREG command as explained on datasheet page 36."""
    GPIO.output(cs, 0)
    firstbyte = 0x10 + register
    secondbyte = 0x01
    spi.writebytes([firstbyte, secondbyte])
    data = spi.readbytes(1)
    GPIO.output(cs, 1)
    return data[0]
 
 

selfcal()

ads1256.selfcal

(

)

Run SELFCAL command as explained on datasheet page 36.

Definition at line 303 of file ads1256.py.

def selfcal():
    """Run SELFCAL command as explained on datasheet page 36."""
    GPIO.output(cs, 0)
    spi.writebytes([0xf0])
    GPIO.output(cs, 1)
    while True:
        if (GPIO.input(drdy) == 0):
            break
 
 

sync()

ads1256.sync

(

)

Run SYNC command as explained on datasheet page 37.

Definition at line 328 of file ads1256.py.

def sync():
    """Run SYNC command as explained on datasheet page 37."""
    GPIO.output(cs, 0)
    spi.writebytes([0xfc])
    GPIO.output(cs, 1)
 
 

twos_complement_to_integer_24bit()

ads1256.twos_complement_to_integer_24bit

(

twos_complement

)

Convert a 24 bit twos complement value to a plain Python integer.

Definition at line 386 of file ads1256.py.

def twos_complement_to_integer_24bit(twos_complement):
    """Convert a 24 bit twos complement value to a plain Python integer."""
    result = twos_complement
    if (twos_complement & (1 << 23)):
        result = twos_complement & ~(1 << 24)
        result = -(1 << 24) + result
    return result
 
 

wakeup()

ads1256.wakeup

(

)

Run WAKEUP command as explained on datasheet page 37.

Definition at line 335 of file ads1256.py.

def wakeup():
    """Run WAKEUP command as explained on datasheet page 37."""
    GPIO.output(cs, 0)
    spi.writebytes([0xff])
    GPIO.output(cs, 1)
 
 

wreg()

ads1256.wreg	(		register,
			data )

Run WREG command as explained on datasheet page 36.

Definition at line 294 of file ads1256.py.

def wreg(register, data):
    """Run WREG command as explained on datasheet page 36."""
    GPIO.output(cs, 0)
    firstbyte = 0x50 + register
    secondbyte = 0x01
    spi.writebytes([firstbyte, secondbyte, data])
    GPIO.output(cs, 1)
 
 

write_adcon_reg()

ads1256.write_adcon_reg

(

)

Write the ADCON register.  See datasheet page 31.

Definition at line 363 of file ads1256.py.

def write_adcon_reg():
    """Write the ADCON register.  See datasheet page 31."""
    wreg(register_address['adcon'], register_data['adcon'])
 
 

write_drate_reg()

ads1256.write_drate_reg

(

)

Write the DRATE register.  See datasheet page 32.

Definition at line 368 of file ads1256.py.

def write_drate_reg():
    """Write the DRATE register.  See datasheet page 32."""
    wreg(register_address['drate'], register_data['drate'])
 
 

write_mux_reg()

ads1256.write_mux_reg

(

)

Write the MUX register.  See datasheet page 31.

Definition at line 373 of file ads1256.py.

def write_mux_reg():
    """Write the MUX register.  See datasheet page 31."""
    wreg(register_address['mux'], register_data['mux'])
 
 

write_status_reg()

ads1256.write_status_reg

(

)

Write the STATUS register.  See datasheet page 30.

Definition at line 378 of file ads1256.py.

def write_status_reg():
    """Write the STATUS register.  See datasheet page 30."""
    wreg(register_address['status'], register_data['status'])
 
 
# Functions that convert
 
 

Variable Documentation

cs

int ads1256.cs = 22

Definition at line 114 of file ads1256.py.

drdy

int ads1256.drdy = 17

Definition at line 115 of file ads1256.py.

max_speed_hz

ads1256.max_speed_hz

Definition at line 406 of file ads1256.py.

mode

ads1256.mode = 'analog'

Definition at line 118 of file ads1256.py.

output

int ads1256.output = -1

Definition at line 120 of file ads1256.py.

register_address

ads1256.register_address

Initial value:

=  dict([('status', 0x00),
                        ('mux', 0x01),
                        ('adcon', 0x02),
                        ('drate', 0x03),
                        ('gpio', 0x04),
                        ('ofc0', 0x05),
                        ('ofc1', 0x06),
                        ('ofc2', 0x07),
                        ('fsc0', 0x08),
                        ('fsc1', 0x09),
                        ('fsc2', 0x0a)])

Definition at line 122 of file ads1256.py.

register_data

ads1256.register_data

Initial value:

=  dict([('adcon', 0x00),
                    ('drate', 0x00),
                    ('fsc', 0x000000),
                    ('gpio_direction_bitmask', 0x00),
                    ('gpio_status_bitmask', 0x00),
                    ("mux", 0x00),
                    ('ofc', 0x000000),
                    ('status', 0x00)])

Definition at line 134 of file ads1256.py.

spi

ads1256.spi = spidev.SpiDev()

Definition at line 404 of file ads1256.py.