The dataq_binary module

Autogenerated API documentation for dataq_binary

DataQ Binary protocol driver

To get started using the one of the supported DataQ data cards, use one of the sub-classes of DataQBinary e.g. DI1110, set scan list and start:

# Instantiate dataq object
dataq = DI1110('/dev/ttyUSB0')

# Get all available information from the data cards
print(repr(dataq.info()))

# Set sample rate frequence
dataq.sample_rate(1000)

# Set scan list (meaure on channel 1 first, then 0 and finnaly 2)
dataq.scan_list([1, 0, 2])

dataq.clear_buffer()
dataq.start()
sleep(0.1)
from pprint import pprint
try:
    while True:
        pprint(dataq.read())
        sleep(0.5)
except KeyboardInterrupt:
    dataq.stop()
else:
    dataq.stop()
dataq.clear_buffer()

If the data card is being used on the limit of emptying the data buffer before it overflow, it might be useful to put the calls to read in a try except:

while True:
    try:
        dataq.read()
    except dataq_binary.BufferOverflow:
        # Re-start i.e. stop and start

or, to simple start and stop the card for a short amount of time, if slow measurements, which would otherwise fill buffer are required:

while True:
    dataq.start()
    sleep(0.1)
    dataq.read()
    dataq.stop()
    # We really only need to measure every 10s
    sleep(10)

On some Linux system, at the end of 2017, some models, e.g. the DI-1110 wasn’t automatically mounted. In that case, it can be manually mounted with a command like this one:

sudo modprobe usbserial vendor=0x0683 product=0x1110

On should be possible, on Debian based Linux systems to add an automatic mount rule along the lines of this thread: https://askubuntu.com/questions/525016/cant-open-port-dev-ttyusb0

So, add a new udev rule /etc/udev/rules.d/99-dataq_di1110.rules

with this content:

# /etc/udev/rules.d/99-dataq_di1110.rules
# contains DataQ DI-1110 udev rule to patch default
# rules
SYSFS{idProduct}=="1110",
SYSFS{idVendor}=="0683",
RUN+="/sbin/modprobe -q usbserial product=0x1110 vendor=0x0683"

and aftwerwards run: sudo udevadm control –reload-rules

exception PyExpLabSys.drivers.dataq_binary.BufferOverflow

Bases: Exception

Custom exception to indicate a buffer overflow

class PyExpLabSys.drivers.dataq_binary.DataQBinary(device, serial_kwargs=None)

Bases: object

Base class for DataQBinary driver

end_char = '\r'

Serial communication end character

read_wait_time = 0.001

Wait time between serial write and read

infos = {'device name': 1, 'firmware revision': 2, 'sample rate divisor': 9, 'serial number': 6, 'vendor': 0}

Information items that can be retrieved along with their code number

led_colors = {'black': 0, 'blue': 1, 'cyan': 3, 'green': 2, 'magenta': 5, 'red': 4, 'white': 7, 'yellow': 6}

Supported LED colors along with the code number

buffer_overflow_size = 4095

Buffer overflow size, may be overwritte in sub classes

packet_sizes = {16: 0, 32: 1, 64: 2, 128: 3, 256: 4, 512: 5, 1024: 6, 2048: 7}

Packet sizes and code numbers

__init__(device, serial_kwargs=None)

Initialize local variables

Parameters:

• device (str) – The device e.g: ‘/dev/ttyUSB0’ of ‘COM1’
• serial_kwargs (dict) – dict of keyword arguments for serial.Serial

clear_buffer()

Clear the buffer

info(info_name='all')

Return information about the device

Parameters:info_name (str) – Name of the requested information item(s). If info_name is one the specific info names, (the keys in DataQBinary.infos), a string will be returned with the value. If info_name is ‘all’, all values will be returned in a dict Returns:Information items Return type:str or dict

start()

Start data acquisition

stop()

Stop data acquisition

This also implies clearing the buffer of any remaining data

scan_list(scan_list)

Set the scan list

The scan list is the list of inputs to acquire from on the data card. The scan list can hold up to 11 items, since there are a total on 11 inputs and each element can only be there once. The analogue input channel are numbered 0-7, 8 is the counter channel, 9 is the rate channel and 10 is the general purpose input channel. 0.7 are specified only by their number, 8, 9 and 10 are configured specially, which is not described here yet.

Parameters:scan_list (list) – Etc. [3, 5, 0] for analogue input chanel 3, 5 and 0. NOTE: The numbers are integers, not strings.

sample_rate(rate)

Set the sample rate

The value values are calculated as being in the range of

sample rate divisor / 375 to sample rate divisor / 65535

So e.g. for the DI-1110 product, with a sample rate divisor of 60,000,000, the valid inputs are in range from 915.5413 to 160000.

Parameters:rate (float) – The sample rate given in number of elements in the scan list sampled per second (i.e. in Hz). Valid values depend on the model and is given by the “sample rate divisor” information item (see the info method). See information about how to calculate the valid input range above.

packet_size(size)

Set the packet size

The packet size is he amount of data acquired before it is placed in the read buffer. The available packet sizes are the keys in packet_sizes class variable.

Parameters:size (int) – The requested packet size

led_color(color)

Set the LED color

Parameters:color (str) – The available colors are the keys in the led_colors class variable

read()

Read all values waiting

This method reads all available damples from the data card and returns for every channel the mean of those samples.

The returned data is on the form of a list with one item for each item in the scan list and in the same order. Each of the items is in them selves a dict, which holds the mean value of the samples, the number of samples in the mean, the channel number (0-based) and information about how full the data buffer was, at the time when it was read out. An example could be:

[{'buffer_status': '3040/4095 bytes',
  'channel': 1,
  'samples': 506,
  'value': -1.6224543756175889},
 {'buffer_status': '3040/4095 bytes',
  'channel': 0,
  'samples': 507,
  'value': -0.0044494267751479287},
 {'buffer_status': '3040/4095 bytes',
  'channel': 2,
  'samples': 507,
  'value': 1.6192735299556213}]

where the scan list was set to [1, 0, 2].

Returns:

A list of values for each of the items in the scan-list and

in the same order. For details of returns values see above.

Return type:list Raises:BufferOverflow – If the buffer was full at the time of reading. The behavior in this case is ill-defined, so it is better to re-start the measurement if that happens.

class PyExpLabSys.drivers.dataq_binary.DI1110(device, serial_kwargs=None)

Bases: PyExpLabSys.drivers.dataq_binary.DataQBinary

FIXME

PyExpLabSys.drivers.dataq_binary.module_test()

Run primitive module tests