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Code for the W7-X gas-puff imaging diagnostic FPGA, data acquisition and control server, and GUI.

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W7-X gas puff imaging diagnostic

Installing the GPI control system code

Clone this repo or download the files. middle_server.py and gui.py each depend on other files in the repo. Install the required python packages with

pip3 install -r requirements.txt

Set the correct addresses in middle_server.py and gui.py:

  • middle_server.py must have RP_HOSTNAME set to the hostname or IP address of the Red Pitaya (RP)
  • gui.py must have MIDDLE_SERVER_ADDR set to "hostname_or_ip:50000" where hostname_or_ip is for the machine on which the middle server is running

Using the GPI control system code

A "middle server" is required to bridge communication between the GUI and RP, and will eventually take care of uploading data to the Archive. The middle server and the GUI can be run on different computers or the same computer.

You can run the middle server with

python3 middle_server.py

In a separate terminal, you can run the GUI with

python3 gui.py

The GUI looks like this:

  • For valve and shutter buttons in the diagram, red = closed, green = open, and black = unknown
  • Valve and shutter buttons can be clicked to toggle between open/closed
  • The "Cancel and reset valves" button can be clicked to interrupt any pump/fill/puff operation and reset the valves to the default configuration
  • You can hover the mouse over some UI elements to see help text

Hardware and software T0/T1 triggers

The user can switch between hardware and software T1 modes by modifying the SOFTWARE_T1 variable in gui.py. "Software T1" mode does all slow valve and fast valve actions automatically after the user presses the T0 button. "Hardware T1" mode requires the user to press the T0 button, then supply a hardware T1 signal approximately N seconds after T0, where N is controlled by the PRETRIGGER variable that must be set near the top of middle_server.py and gui.py files. The time between software T0 and hardware T1 must be accurate to within less than 1 second.

⚠️ Hardware T1 mode uses a signal on RP pin DIO1_P (H16). Even if you are doing software T1 triggering, this pin should be kept at a low voltage because a hardware T1 can occur due to the floating voltage.

FPGA documentation

Overview

The RP running the code in koheron-sdk/instruments/GPI_RP has two jobs:

  • Send open or close signals to several different valves
  • Monitor pressure readings from two gauges using two fast analog inputs

For information on the pins and their various functions and names, see this documentation.

Valve control

RP outputs are connected to the black box, which contains

  • "Card 1"
    • Fast circuit board 1
    • Fast circuit board 2 (backup, not currently in use)
  • "Card 2": slow valve circuit board

For more information, see the circuit schematics for the black box.

Slow valves

These valves do not require precise timing to open or close. The following RP pins control them:

J18 slow_1_manual (called V5 in GUI)
K17 slow_2_manual (V4)
L14 slow_3_manual (V3, expects and returns inverted values rel. others)
L16 slow_4_manual (not used)

Fast valves

This valve will need to open/close at precise times. The timing logic is implemented in the RP trig_delay core. The timer starts after a T1 signal is supplied, currently through the python/C++ bridge but eventually this will be a real signal going to one of the pins.

There is only one fast valve, but there are two fast actuating circuits for redundancy. We will have circuit 1 hard-coded in the RP logic and can switch to circuit 2 if it fries. Each circuit uses different pins to communicate with the RP. To actuate the valve with the timing logic, each circuit requires both an open/close pulse and a constant permission signal. Each circuit has "registers" for two separate actuations (order doesn't matter), and this entails two open/close pins and two permission pins. The valves can also be actuated manually at any time without permission using a different set of pins—we won't be using this feature regularly.

# Fast circuit card 1
G18 fast_manual        (actuate FV2 at any time without permission)
H17 fast_permission_1  (required for fast_puff_1 signal to pass through black box)
H18 fast_puff_1        (pulse to open/close)
K18 fast_permission_2  (required for fast_puff_2 signal to pass through black box)
L15 fast_puff_2        (pulse to open/close at a second time)

# Fast circuit card 2
L17 fast_manual
J16 fast_permission_1
M15 fast_puff_1
K16 fast_permission_2
M14 fast_puff_2

Note that there is also a "w7x permission" signal going to the black box. This is processed by the black box, and not the RP, but the RP can view its value (binary low/high) in the status register named W7X_permission as the signal is connected to RP pin G17.

Pressure monitoring

Every 0.1 ms, the data_collector core on the RP takes two 14-bit readings from two fast analog inputs and glues them together in a zero-padded 32-bit number before sending them to a FIFO queue core. This queue is checked every 1 ms and entries are stored in the C++ adc_data_queue as they are popped off. When queried via Python, adc_data_queue will get copied to the adc_data vector by popping all its entries, and the vector will be returned.

Modifying the FPGA code

To compile the FPGA code after any modifications requires Vivado 2017.4, which can be downloaded for free (you will need to register for an account though). It takes up about 15 GB of space.

Crucial FPGA code files

In koheron-sdk/instruments/GPI_RP:

Viewing the FPGA block diagram

In the koheron-sdk directory, do

make CONFIG=instruments/GPI_RP/config.yml block_design

Here is the block design as of this writing (March 2021):

Compiling the FPGA code

In the koheron-sdk directory, do

make CONFIG=instruments/GPI_RP/config.yml all

Uploading FPGA code to the RP

In the koheron-sdk directory, do

make CONFIG=instruments/GPI_RP/config.yml HOST=hostname_or_IP_of_RP run

or if you have the GPI_RP.zip file in your current directory, and you can ping the RP from your computer, simply do

HOST=hostname_or_IP_of_RP
NAME=GPI_RP
INSTRUMENT_ZIP=./GPI_RP.zip
curl -v -F $(NAME).zip=@$(INSTRUMENT_ZIP) http://$(HOST)/api/instruments/upload
curl http://$(HOST)/api/instruments/run/$(NAME)

Debugging the RP C++ server

The server should produce /root/errs.log and /root/reqs.log files on the RP.

View additional koheron-server log messages (including ctx.log<INFO>('some info') statements in C++) with

journalctl -u koheron-server 

For real debugging, add/uncomment this line in koheron-sdk/server/server.mk:

SERVER_CCXXFLAGS += -fsanitize=address,undefined -O0 -g

Then you can compile the server binary directly on the RP:

make -C /git/GPI_W7-X/koheron-sdk clean server
/tmp/live-instrument/serverd
gdb --pid=$(pidof serverd)

Other RP configuration details

In /usr/lib/arm-linux-gnueabihf on the RP, symlink libstdc++.so.6 has been changed to point at libstdc++.so.6.0.22 (instead of libstdc++.so.6.0.21 originally), copied from Xilinx/SDK/2017.4/gnu/aarch32/lin/gcc-arm-linux-gnueabi/arm-linux-gnueabihf/lib. This fixed an error that was being thrown by serverd.

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Code for the W7-X gas-puff imaging diagnostic FPGA, data acquisition and control server, and GUI.

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