Spencer Pollard
In Progress Data Acquisition GitHub
I began working in the lidar group in November of 2023 and worked over the winter break
separating the Fall 2023 and Spring 2024 semesters. My core project over the winter break is to
work on developing a new data acquisition program in Python moving away from LabVIEW for the REAL.
The new program should follow the flowchart below:
The data acquisition program should be sitting, waiting for a trigger event to begin data collection.
Once that signal is provided, the following things should all happen at the same time:
- Capture waveform data using the NI PCI-5122 Oscilloscope Card ✅
- Get azimuth and elevation angles from servo motor positions 🚧
- Get pulse energy ❌
- Get date and time ✅
- Get pitch and roll ❌
- Get Raman temperature and pressure ❌
(✅ means complete, ❌ means incomplete, 🚧 means partial completion)
My wholistic approach to this project will be to use Tkinter to create a GUI program to create the front end of the data acquisition software. I'm using Python because it's how I know how to do what is desired and because it's more "new user" friendly. If possible, I would like to translate the entire software to something like C which is faster than Python, but I don't believe speed is a current bottleneck.
Below represents the log where I will be recording my progress on the deliverables above to help guide future students who wish to resume my work.
Creating the GUI
My first approach to this was using Tkinter because at the time that's what I knew existed, and it wasn't until after I started when Dr. Eric Ayars informed me of the existence of PyQt5. I will show my initial DAC program followed by the most recent one. The DAC software should (for the most part) be a front end GUI application that simple shows the status of the data acquisition processes with a few controls to change whether or not the data is being broadcast on a network socket or whether or not the data should be written to disk.
Tkinter
This first approach was attempting to combine and integrate all the different things that the DAC should be able to do and display them. I am not well-versed with Tkinter nor GUI design so my objective is just to get a window that works and will display everything that we need for data acquisition. What I will be doing is adding particular controls for the desired deliverables. For example, shown below is the state of the DAC application after integrating the waveform data collection.
PyQt5
This second approach was centred around what the DAC should actually do. As mentioned above, the main DAC program runs while the LiDAR is operating and should simply display the statuses of the underlying data acquisition processes. Each box in the image below represents one of the core functions that this DAC program manages with a status light as well as a box that will display that reading. The topmost box with the trigger pulse is a testing light that will flash being triggered by the incoming signal to the PCI-5122 Oscilloscope card.
Capture waveform data using the NI PCI-5122 Oscilloscope Card
I wrote a "How To" here for how I went about interfacing NI DAQ peripherals where I show the exact code I used to interface the PCI-5122 card using Python. Basically, I'm taking the code from there and putting it inside a function that I can call from the main DAC program. That code is in capture_waveforms.py. The short answer for how I went about doing this is first look at how I can do this using NI MAX and begin translating that process to Python. Basically, for data acquisition you need a task (which NI MAX can do) and then you specify what that task should do (e.g. measure a voltage on a specific pin, count pulses, etc). In this case, we're measuring a voltage on an analog input pin. As of writing this, the current program for this requires a specific number of samples and a sample rate. I believe the correct approach to this would be waiting for data to exist before starting collection and then stopping once there's no more data. But for testing, this works just fine.
Communicating with Animatics Servo Motors over Serial CommunicationI wrote a "How To" here for how I went about interfacing NI DAQ peripherals where I show the exact code I used to interface the PCI-5122 card using Python. Basically, I'm taking the code from there and putting it inside a function that I can call from the main DAC program. That code is in capture_waveforms.py. The short answer for how I went about doing this is first look at how I can do this using NI MAX and begin translating that process to Python. Basically, for data acquisition you need a task (which NI MAX can do) and then you specify what that task should do (e.g. measure a voltage on a specific pin, count pulses, etc). In this case, we're measuring a voltage on an analog input pin. As of writing this, the current program for this requires a specific number of samples and a sample rate. I believe the correct approach to this would be waiting for data to exist before starting collection and then stopping once there's no more data. But for testing, this works just fine.
This was the longest and most complicated thing I have worked on relating to this project so far. The Animatics servo motors use their own proprietary language (similar to BASIC) to program them over RS-232 serial ports. So, I attempted to write a Python script that will allow me to build the instructions for the motor and send them. This script is the class that is in the animatics_motor_interface.py file. It creates a temporary directory and stores a log file there, and it creates a "program" object that has the ability to write to this logging file as well as keep track of the file's data (so it doesn't always reference a file for what data to write to the motor). This program object then has methods that allow the user to write specific commands to the motor (as also specified here). There are a ton of commands that these motors have so I'm more or less implementing the ones I need as I go. I don't know if the commands themself need to be in HEX, but I've encoded all the strings into ASCII before converting everything into HEX and then sending it over the serial line. This workaround makes it so the user doesn't have to deal with the SMI Interface to do anything with these motors, but the user will need to know how the program flow works [maybe make a How To for this?].
Getting Azimuth and Elevation Angles From Servo Motor Positions
To do this, I am attempting to interface the Animatics Model SM3420D servo motors using an NI PCIe-6323 Multifunction I/O card with an NI SCC-68 Terminal Block. I built a couple of cables to properly connect the 7W2 Combo D-Sub Connector and P2 DB-15 D-Sub Connector with my computer and the PS42V6AG-110 48VDC power supply. I connected the positive and negative terminals of the CBLDC1 cable to the appropriate pins on the 7W2 Combo D-Sub connector and the remaining RS-232 data transmission related pins to a RS-232 connector. This allowed me to power the motor and communicate with it using the Animatics SmartMotor Interface (this was before I wrote my own Python interface). Once I could power and connect the motor, I needed to check the signal from the interal encoders to make sure the proper pulse trains are made and are measurable.
The leftmost image shows the screw terminals that I'm using from the SCC-68. The red wire is "Encoder A" from the motor screwed into terminal 37, the green wire is "Encoder B" from the motor screwed into terminal 38, and the white wire is ground screwed into terminal 67.
The centre image is just the rough setup I have showing that I have the motor plugged into both the SCC-68 and into the RS-232 port on my computer. The rightmost image is showing me the two different pulse trains from each encoder from the motor. These pulse trains should be 90 degrees out of phase.
From the pulse trains, we should be able to determine how far the motor moved from its initial zero point which means we should be able to determine the angle it's rotated at. [IN PROGRESS]
To do this, I am attempting to interface the Animatics Model SM3420D servo motors using an NI PCIe-6323 Multifunction I/O card with an NI SCC-68 Terminal Block. I built a couple of cables to properly connect the 7W2 Combo D-Sub Connector and P2 DB-15 D-Sub Connector with my computer and the PS42V6AG-110 48VDC power supply. I connected the positive and negative terminals of the CBLDC1 cable to the appropriate pins on the 7W2 Combo D-Sub connector and the remaining RS-232 data transmission related pins to a RS-232 connector. This allowed me to power the motor and communicate with it using the Animatics SmartMotor Interface (this was before I wrote my own Python interface). Once I could power and connect the motor, I needed to check the signal from the interal encoders to make sure the proper pulse trains are made and are measurable.
The leftmost image shows the screw terminals that I'm using from the SCC-68. The red wire is "Encoder A" from the motor screwed into terminal 37, the green wire is "Encoder B" from the motor screwed into terminal 38, and the white wire is ground screwed into terminal 67.
The centre image is just the rough setup I have showing that I have the motor plugged into both the SCC-68 and into the RS-232 port on my computer. The rightmost image is showing me the two different pulse trains from each encoder from the motor. These pulse trains should be 90 degrees out of phase.
From the pulse trains, we should be able to determine how far the motor moved from its initial zero point which means we should be able to determine the angle it's rotated at. [IN PROGRESS]
Get Date and Time
This is very straightforward in implementation. I'm using the datetime libary's
What Remains to Be CompletedThis is very straightforward in implementation. I'm using the datetime libary's
now() function to get the current date and time of when things happen in the DAC software and just print them to a textbox for the time being. This is held in the DAC.py file (outdated) in the function get_date_and_time() where I'm formatting it in a particular way.
I only had about 3 weeks working part time hours to get as much done as I could. The things that remain to be completed are:
- Interpretting servo motor pulse trains to determine motor's relative position
- Get pulse energy
- Get pitch and roll
- Get Raman temperature and pressure
Back to Lidar Team.