Code for communicating between CASPER's ROACH2 + 5 Gs/s ADC, Velmex VXM motor controller + B59 rotary table, and Python 2.7.

• adc5g
• fit_cores
• corr
• pyserial
• ntplib
• h5py
• numpy
• scipy
• matplotlib
• tqdm
• vxi11

All can be installed (as root) with $ pip install <packagename> except:

• adc5g:

$ pip install git+git://github.com/sma-wideband/adc_tests.git

• fit_cores:

$ wget https://raw.githubusercontent.com/sma-wideband/adc_tests/master/fit_cores.py
$ mv fit_cores.py /Library/Python/2.7/site-packages

or wherever Python's sys.path is on your system.

• spec.py - A class that initializes a 2048 channel spectrometer on the ROACH board.
• motor.py - A class capable of stepping and reading back the position of the rotary table.
• time_sync.py - Contains functions that determine the system time's offset from UTC using the nearest NTP server.
• in_out.py - Contains functions that read and write arrays of measured spectra along with their associated metadata to and from hdf5 files on disk.
• scan.py - A routine that combines the above methods to measure and record spectra over a range of elevations.

To execute a data run with the default parameters:

$ python scan.py go

or in an IPython terminal:

In [1]: run scan.py go

To execute a data run with non-default parameters, call go() directly:

In [1]: run scan.py

Usage: "python scan.py go"

In [2]: go(step = 1, home = False, min = 0, max = 45, zenith = 0, samp_rate = 4400, acc_len = 1,
           n_accs = 20, port = '/dev/ttyUSB0', ip = '128.135.52.192') # default args

go() initializes Spec, Motor, and h5py.File objects in order write n_accs accumulations to files in the output directory at angles separated by step degrees, each one acc_len seconds long, from min to max degrees away from the zenith position of the motor.

Each time the motor returns to zenith, the script closes the current output file and opens a new one. All output files are automatically named with the current UTC time, which is calculated at each return to home by querying an NTP server for the system time's offset from UTC. File I/O and time syncronization operations are accomplished with functions in in_out.py and time_sync.py.

To create a standalone spectrometer instance, run:

from spec import Spec
s = Spec(samp_rate = 4400, acc_len = 1, ip = '128.135.52.192') # default args

The __init__ block prints its progress:

Connecting to "128.135.52.192"
Loading "simple_spec.bof"
Deglitching
Setting sample rate to 4400 MHz
Setting accumulation length to 1s
Setting fft shift
Arming PPS

Upon rebooting the board, the offset, gain, and phase registers for each of the four cores on the ADC will be cleared. It is recommended that you run:

s.fit_ogp(10) # frequency of test tone in MHz

which prints the best-fit values for OGP as determined by a least-squares fit to a sine function at the provided frequency:

# 10.00  zero(mV) amp(%)  dly(ps) (adj by .4, .14, .11)
#avg    -0.1680 125.1196 49038.3687
core A  -0.1939 -0.0382 -29.7747
core B  -0.4248 -0.2018 -73.7172
core C   0.2916 -0.0505 -68.5566
core D  -0.3448  0.2905 172.0485

sinad = 34.37
average of 2 measurements
#avg    -0.1680 125.1196   0.0000
core A  -0.1939 -0.0382 -29.7747
core B  -0.4248 -0.2018 -73.7172
core C   0.2916 -0.0505 -68.5566
core D  -0.3448  0.2905 172.0485

You can plot the time series data with each core denoted seperately to verify that the fit was succesful:

plt.ion()
s.plot_time(cores = True)

If the fit was succesful, you can save the OGP settings to output/ogp.npy and load them again using

s.save_ogp()
s.load_ogp()

To create an instance of the Motor class, run:

from motor import Motor
m = Motor(port = '/dev/ttyUSB0', baudrate = 38400) # default args

You can save settings to the VXM controller with m.save_settings() - this is how we can initialize the class to a baudrate of 38400, even though the controller's factory baudrate is 9600.

The home() method makes use of the B59 rotary table's magnetic limit switch to acheive 0.01 degrees of angular precision. This method, along with incr() and abst() returns a boolean value of its success, rather than the raw writeback. If raw writeback is desired, use the send() method.

For safety reasons, a KeyboardInterrupt or SystemExit during send_command() will trigger the command "D", which decelerates the motor to a stop. Default acceleration and speed are set to 1 and 20, and can be changed with m.accl and m.speed, or else specified with optional arguments in incr() and abst().

In addition to the sma_wideband code that we import verbatim:

• The initialization and snapping methods in Spec are derived from Jack Hickish's simple_spec.
• The OGP fitting methods in Spec are derived from Rurik Primiani's rww_tools.