Ubitekk CC1 User manual
CC1‐Handheld
CoincidenceCounter
USER’SMANUAL
Rev.1.02
June1,2015
www.qubitekk.com
Contents
1. Principle of Operation 1
1.1 Overview..........................................................................................................................1
1.2 What is Included...............................................................................................................1
1.3 Powering the Unit.............................................................................................................2
1.4 Navigating the Menus ......................................................................................................3
1.5 Setting up a Measurement...............................................................................................5
1.6 Making a Measurement....................................................................................................6
2. Settings 7
2.1 Description of Counting Process......................................................................................7
2.2 Coin Window....................................................................................................................8
2.3 Dwell Time .......................................................................................................................8
2.4 Gate Chan........................................................................................................................8
2.5 Subtract Acc.?..................................................................................................................8
2.6 Trigger..............................................................................................................................9
2.7 CH1 Delay........................................................................................................................9
2.8 Firmware..........................................................................................................................9
3. Serial Interface 10
3.1 Serial Interface Setup.....................................................................................................10
3.2 Programming Commands ..............................................................................................10
3.3 Sample Code .................................................................................................................11
4. Customization 12
4.1 Overview........................................................................................................................12
4.1.1 The Rabbit RCM3400 Microprocessor.....................................................................13
4.1.2 The Altera Cyclone IV FPGA ...................................................................................13
4.1.3 Default Firmware......................................................................................................13
4.2 Uploading Custom Firmware..........................................................................................14
4.2.1 Accessing the Programming Ports...........................................................................14
4.2.2 Programming the Rabbit RCM3400.........................................................................15
4.2.3 Programming the Cyclone IV FPGA ........................................................................18
Appendix A. Electrical Schematics and Connections 20
A.1 Top Board (LCD Board).................................................................................................21
A.2 Bottom Board (Processor Board)...................................................................................22
A.3 Pinout Table...................................................................................................................25
1
Principle of Operation
1.1 Overview
The CC1 is a low-cost, handheld coincidence counter intended for use with single photon
counting experiments. The unit can detect and count TTL electrical pulses with nanosecond
resolution and a maximum count value of 2,097,152 pulses per channel. Pulses that occur
simultaneously on Channel 1 and Channel 2, within a specified “coincidence window,” are
treated as “coincident” pulses and are measured and displayed by the unit (max coincidence
count equal to 2,097,152).
An LCD display on the front of the unit allows easy viewing of all measured single and
coincidence counts. This display, in addition to the push buttons on the front of the unit,
provides a simple interface for displaying results and setting up measurements. A USB
connection on the side of the unit provides power to the system while also allowing for optional
serial control of the device by a computer.
The CC1 comes pre-programmed with all of the functionality described in this manual; however,
it is capable of much more. The unit contains both a re-programmable microprocessor (for
handling the user interface and serial communications) and a re-programmable FPGA (for
handling high-speed pulse counting). Both of these devices can be programmed by the user to
implement a wide range of features.
In the Appendix section, the user will find the necessary documentation for programming the
CC1 for custom applications. Whether it is implementing a time histogram recorder,
expanding/modifying the existing features of the CC1, or developing a custom device for use in
implementing new cryptographic protocols, the CC1 is a flexible platform that will greatly simplify
and speed your development effort.
1.2 What is Included
The CC1 Handheld Coincidence Counter ships with the following materials:
a) 2m USB cable (USB-B)
b) CC1 Coincidence Counter
c) Rabbit programming cable (2mm)
d) Retractable USB cable (USB-mini)
e) Development software and programming file
f) USB-to-AC power module
The various components (with their respective labels) are shown in Figure 1 on the following
page.
2
Figure 1. Components included with CC1 Coincidence Counter.
1.3 Powering the Unit and Connecting Inputs
The CC1 is powered through its USB port. The USB cable provided with the system should be
plugged into the side of the unit as shown in Figure 2.
Figure 2. Power over USB connection.
The other end of the USB cable can be plugged into a computer USB port or plugged into the
included USB-to-AC power connector, as shown in Figure 3.
a
b
c
def
3
Figure 3. USB-to-AC Adapter.
Once powered, the CC1 will display a startup screen for five seconds on the unit’s blacklit LCD.
The unit’s “Count Screen” will then be displayed as shown in Figure 4.
Figure 4. Count Screen on startup.
To connect signals to the CC1, three SMA connector jacks are available at the top of the unit.
To detect coincident pulses, Channels 1 and 2 must both be connected to a pulse signal. If the
counting of single and coincidence pulses should be gated (see next section for more details),
then the third channel (“GATE”) should be connected to the associated gate pulse.
1.4 Navigating the Menus
The CC1 has six buttons on its front face. The buttons, along with signal connectors and
peripheral ports, are shown in Figure 4.
4
Figure 4. CC1 Buttons and Ports.
5
To configure the CC1 for a measurement, press the“menu” button. The CC1’s Menu Screen
will be displayed as shown in Figure 5.
Figure 5. Menu Screen.
Pressing the “menu” button again will return the user back to the Count Screen.
The Menu Screen contains six settings that can be changed by the user. These settings will be
covered in the following section. The various settings can be viewed by scrolling up or down in
the menu using the “UP” and “DOWN” arrow buttons.
When a setting needs to be changed, the setting can be selected for modification by pressing
the “ENABLE” button. The setting value will blink, indicating that it is ready for modification.
Again, the UP” and “DOWN” arrow buttons can be pressed to change the setting value. Once
complete, press the “ENABLE” button again to continue scrolling through the menu.
1.5 Setting Up a Measurement
Prior to any measurement, the measurement parameters for the CC1 should be configured. The
next section of the manual will describe each parameter and discuss their impact on the
measurement. The default settings for the CC1 (upon power up) are shown in Table 1 below:
Setting Value
Coincidence Window 1 ns
Dwell Time 2 s
Gate Chan. Disabled
Subtract Acc.? No
Trigger Start/Stop
CH1 Delay 0 ns
Firmware Ver 2.001
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1.6 Making a Measurement
Once all measurement settings have been adjusted, the “menu” button should be pressed to
return to the Count Screen. With the Count Screen displayed, press the “ON/OFF” button to
start or end a count.
Once the “ON/OFF” button has been pressed, the details of the count measurement will be
displayed on the LCD as shown in Figure 6.
Figure 6. Count Screen after measurement.
Once the measurement is complete, the counts will remain on the screen until a new count is
initiated.
NOTE: If the unit is being triggered in “Continuous” mode, the counts will only remain on the
screen for a short period of time before resetting to zero and beginning the next count.
7
Settings
2.1 Description of Counting Process
Pulses detected on Channel 1, Channel 2, and the optional Gate channel will be counted as
coincident pulses based on a number of settings made prior to the measurements. In general,
the simplest measurement of coincidence is as shown in Figure 7:
Figure 7. Simple coincidence measurement described.
Two pulses will be counted by the CC1 to be coincident if:
a. The time between the rising edges of the two pulses is less than the coincidence window
If the GATE signal is enabled, then the two pulses will only be counted by the CC1 as coincident
if the following two conditions are satisfied:
a. The time between the rising edges of the two pulses is less than the coincidence window
b. The GATE signal is enabled during both rising edges
Figure 8 represents a coincidence measurement with the GATE signal enabled.
Figure 8. Coincidence measurement with a GATE signal.
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With this understanding in place, the remainder of this section will look at how aspects of this
measurement are specified in the CC1.
2.2 Coin Window
If pulses are simultaneously detected within some short time window, then they are said to be
coincident. The CC1 refers to this time window as the Coincidence Window, or “Coin Window”
for short. Technically, the Coin Window is the maximum allowed time between the rising edge of
a pulse on Channel 1 and a pulse on Channel 2 before two pulses are no longer considered to
be coincident.
The Coin Window can be set on the CC1 to be any integer value between 1 and 8
nanoseconds.
2.3 Dwell Time
The Dwell Time is the amount of time to accumulate pulses. For example, if the Dwell Time is
20 seconds, then all single pulses detected on Channel 1 during a 20 second measurement
period would be totaled and displayed. This would also be true for Channel 2 and the coincident
channel.
The Dwell Time can be set on the CC1 to values ranging between 0.1 second and infinity. When
a measurement is initiated, the CC1 will accumulate counts for an amount of time equal to the
Dwell Time. If the Dwell Time is infinity, the CC1 will accumulate counts indefinitely or until the
ON/OFF button is pressed and the count process stopped.
2.4 Gate Chan.
The Gate Chan. setting determines whether or not the GATE channel performs any function. If
the Gate Chan. value is set to “ENABLED,” single and coincidence counts will only be detected
when the GATE signal is high. If the Gate Chan. value is set to “DISABLED,” the GATE signal
will be ignored.
2.5 Subtract Acc.?
In some experiments, the CC1 may be used to measure coincidence counts to identify
correlations between signals. Coincidence counts can often indicate the presence of some
shared source of photon generation or optical phenomena. However, coincidence counts can
also be the results of random chance.
Statistically, there is some probability that a random stream of pulses on Channel 1 will
occasionally produce a pulse that is coincident with another random stream of pulses on
Channel 2. This statistical likelihood is called the “accidentals” and it can be calculated using the
following formula:
(sec)timedwell Singles#2ChannelSingles#1Channel(sec)WindoweCoincidenc2
sAccidental
9
Because accidentals can sometimes obscure the true correlations being sought in an
experiment, it can be advantageous to have these accidentals automatically calculated and
subtracted from the measured coincidence value.
The Subtract Acc.? setting allows the user to turn this calculation on or off. If the Subtract Acc.?
value is set to “YES,” then the estimated accidentals will be calculated and subtracted from all
coincidence measurements. If the Subtract Acc.? value is set to “NO,” then the full coincidence
counts (with accidentals included) will be reported.
2.6 Trigger
The Trigger setting allows the user to select how a measurement will be started and stopped. If
the Trigger setting is set to “Continuous,” then the measurements will start once the ON/OFF
button is pressed. Once a count is initiated, the unit will accumulate counts for the set Dwell
Time. Once the Dwell Time has been reached, the total counts accumulated will be shown on
the counter’s display for a short period of time. Then the unit’s counters will automatically be
reset and a new count initiated. This cycle will continue over and over until the ON/OFF button
is again pressed to halt continuous triggering.
If the Trigger setting is set to “Start/Stop” then a new count will be initiated only when the
ON/OFF button is pressed. Once a count is started, the count will continue until either the dwell
time is reached or the ON/OFF button is pressed again to stop the counting cycle.
2.7 CH1 Delay
The signal coming into the Channel 1 connector can be delayed by adjusting the “CH1 Delay”
setting. Adding a delay to a channel can be useful when searching for coincident events in
signals that may be delayed. For example, if the cable from one photon detector is one meter
long while the cable from a second photon detector is two meters long, then there will be a
transmission delay of roughly 5 ns that must be subtracted to detect coincident events.
The CH1 delay setting allows delays of 0, 2, 4, 6, 8, 10, 12, and 14 ns to be programmed into
the CC1.
2.8 Firmware Ver.
The firmware version is a four digit identifier of the CC1’s firmware release version. This setting
cannot be changed by the user.
10
Serial Interface
3.1 Serial Interface Setup
The CC1 has an emulated COM port for serial communication, and uses SCPI-compliant
commands. To use the serial interface, use the included USB-B 2m cable to connect the CC1 to
a computer USB port. The USB cable allows the CC1 to both receive power and send data over
the USB connection.
To communicate with the CC1, download a serial terminal emulator program (such as RealTerm
or PuTTY on Windows) or send serial commands through your own custom program. The serial
interface settings should be configured with the following settings:
Setting Value
Baud Rate 19200 bps
Data bits 8
Parity None
Stop Bits 1
Flow Control None
3.2 Commands
The following serial commands can be used to control/interface the CC1 unit with a computer or
microcontroller. If a command is not recognized, the CC1 will reply with “Unknown Command.”
Command Description
COUN:C1?
(:C2?)(:CO?) Returns the current value on the counter, either Channel 1 (C1), Channel 2 (C2),
or Coincidences (CO)
:CLEA Sends the clear signal to the counters
:DELA N Set the delay value (in nanoseconds) on Channel 1. N may be 0, 2, 4, 6, 8, 10, 12,
or 14ns.
:DELA? Returns the delay value on Channel 1 in nanoseconds
:DWEL N Sets the dwell time to N seconds. N must be equal to or greater than 0.1 and
cannot be more than 5 characters long (including the decimal point).
DWEL? Returns the dwell time in milliseconds
FIRM? Returns the firmware release identifier
:GATE N Sets whether or not the GATE channel is enabled: 0 = No, 1 = Yes
GATE? Returns whether or not the GATE channel is enabled: 0 = No, 1 = Yes
:SUBT N Sets whether or not to subtract accidentals from coincidence rate: 0 = No, 1 = Yes
SUBT? Returns value indicating if accidentals are being subtracted from coincidences: 0 =
No, 1 = Yes
:TRIG N Sets the trigger value: 0 = Continuous, 1 = Start/Stop
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Command Description
TRIG? Returns the value of the trigger setting: 0 = Continuous, 1 = Start/Stop
:WIND N Sets the coincidence window length to N nanoseconds. N must be between 1 and
8.
WIND? Returns the coincidence window length in nanoseconds
3.3 Sample Serial Program
The following sample program (written in Visual Basic 6.0) provides a very simple example of
how serial commands can be used through third-party programs to control the CC1:
MSComm3.PortOpen = True ‘Open COM Port
'-- Prepare Coincidence Counter for Measurements --
MSComm3.Output = ":GATE 0" & Chr$(13) ‘Disable GATE Channel
Sleep 300 'Wait 0.3 seconds for command to transfer
MSComm3.Output = ":SUBT 0" & Chr$(13) 'Turn off Subtract Accidentals option
Sleep 300 'Wait 0.3 seconds for command to transfer
MSComm3.Output = ":TRIG 1" & Chr$(13) 'Set Trigger Option to Start/Stop
Sleep 300 'Wait 0.3 seconds for command to transfer
MSComm3.Output = ":DWEL 20000" & Chr$(13) 'Set Dwell Time to 20 seconds
Sleep 300 'Wait 0.3 seconds for command to transfer
MSComm3.Output = ":DELA 2" & Chr$(13) 'Set Delay Time on Channel 1 to 2ns
Sleep 300 'Wait 0.3 seconds for command to transfer
MSComm3.Output = ":WIND 3" & Chr$(13) ‘Set Coincidence Window to 3 ns
Sleep 300 'Wait 0.3 seconds for command to transfer
'-- Take Measurement --
MSComm3.Output = ":COUN:ON" & Chr$(13)
dt = Now ' Wait for Dwell Time (plus 1 second)
Do While DateDiff("s", dt, Now) < 21
DoEvents()
Sleep 50 'Put app to sleep in small increments
Loop
'--Transfer Measurements --
MSComm3.Output = "COUN:C1?" & Chr$(13) ‘Query Channel 1 Counts
Sleep 300 'Wait 0.3 seconds for command to transfer
Textbox1.text = MSComm3.Input ‘Display counts in a textbox
MSComm3.Output = "COUN:C2?" & Chr$(13) ‘Query Channel 2 Counts
Sleep 300 'Wait 0.3 seconds for command to transfer
Textbox2.text = MSComm3.Input ‘Display counts in a textbox
MSComm3.Output = "COUN:CO?" & Chr$(13) ‘Query Coincidence Counts
Sleep 300 'Wait 0.3 seconds for command to transfer
Textbox3.text = MSComm3.Input ‘Display counts in a textbox
MSComm3.PortOpen = False ‘Close COM Port
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Customizing the CC1
4.1 Overview
The CC1 is an open-source platform that was developed to give as much flexibility to users as
possible. This means that the internal firmware that operates the device can be changed by the
user, if desired. Inside the CC1, two programmable electronic components are responsible for
most of the functionality of the CC1. They include:
A Rabbit RCM3400 Microprocessor
An Altera Cyclone IV FPGA
The location of these components inside the CC1 is shown below:
Figure 9. Internal view of CC1 electronics.
The RCM3400 microprocessor is used to implement the user interface (i.e. LCD display, menus,
serial communicatons, etc.) as well as some very simple calculations (i.e. accidentals). The
Altera FPGA is used for making high speed measurements (i.e. the coincidence counting).
These two devices can be independently programmed to realize new functionality for a wide
range of applications. For example, the CC1 device could be reprogrammed to timestamp every
photon detection event and create a histogram of the arrival times. Or two CC1s could be re-
programmed to act as a four photon coincidence counter (using the GATE channel as a
RabbitRCM3400module
AlteraCycloneIVFPGA
(onDE0‐Nanoprotoboard)
13
communication signal between the two CC1s). Or the CC1 could be used with other external
devices and serial data to implement a part - or all - of a QKD communication protocol.
Because the electrical components, connections, and user interface are already in place (and
described in Appendix A), the CC1 can serve as a flexible platform for interrogating signals from
single photon detectors and performing associated operations.
4.1.1 The Rabbit RCM3400 Microprocessor
The Rabbit RCM3400 is a microprocessor module consisting of a simple processor integrated
with other general purpose peripheral logic. The device is programmed using a language
proprietary to Rabbit Semiconductor called Dynamic C. Dynamic C is very similar to ANSI C,
with extra functions for interacting with the digital I/O, analog inputs, and PWM outputs on the
RCM3400 module.
To program in Dynamic C, an integrated development environment (Dynamic C 9.62) and
programmer utility (DC 9.62 RFU) must be installed on your computer. A single installation
program (DynamicC_9.62_WebFull.exe) - available on the flash drive that came with your unit
as well as from Qubitekk’s website (www.qubitekk.com) – will install both programs. A
programming cable for uploading new firmware to your CC1 is also required and has been
included with your unit (Rabbit Programming Cable - 2mm)
A great resource for learning Dynamic C and how to program the RCM3400 is the book entitled,
“Embedded Systems Design using the Rabbit 3000 Microprocessor” by Kamal Hyder. Although
this book was published in 2004, it still contains very relevant and useful examples of how to
program and understand the operation of the RCM3400. In addition, manuals for the RCM3400
and Dynamic are available on the flash drive that came with your unit and Qubitekk’s website.
4.1.2 The Altera Cyclone IV FPGA
The Altera Cyclone IV chip is a field programmable gate array (FPGA) that can operate at
frequencies in excess of 1GHz. The chip is particularly well suited to detecting and
timestamping LVTTL pulses (as would be emitted by a single photon counting module). The
chip can be programmed using Altera’s Quartus II Web Edition (version 13+) – which is free and
available at both Altera’s website (www.altera.com) and Qubitekk’s website.
In the CC1, the Altera FPGA is actually part of an off-the-shelf prototyping board (the Terasic
DE0-Nano). This prototyping board has additional functionality that may be used in future
versions of the CC1 product. A manual for the Terasic DE0-Nano is available on the flash drive
that came with your unit as well as Qubitekk’s website.
4.1.3 Default Firmware
The CC1 comes pre-programmed for use as a general purpose coincidence counter. However,
the Dynamic C source code and the FPGA Quartus project files (including verilog modules,
14
block diagrams, pin assignments, board support files and board schematic files) are all included
on the flash drive that came with your unit.
If your device should ever need to be returned to its original operating firmware, the source code
and the programming files to do this are available on the flash drive. In addition, newer versions
of the CC1’s firmware are posted online at Qubitekk’s website and are freely available to all.
The default firmware can be a useful place to start when exploring how to modify your CC1 unit.
Both the source code for the RCM3400 microprocessor and the Cyclone IV FPGA are available
and well commented. Be sure to check the Qubitekk website frequently for the latest versions of
the default firmware.
4.2 Uploading Custom Firmware
4.2.1 Accessing the Programming Ports
To upload new firmware to your CC1, it is necessary to first remove the cover at the bottom of
the CC1. To do so, first remove the six Phillips screws on the back of the CC1 that hold the two
halves of the CC1 instrument case together. With these screws removed, the two halves of the
enclosure can be gently pulled apart (pull each half straight away from the other for easiest
disassembly).
Figure 10. Removal of screws to disassemble CC1.
With the two halves separated, it is now possible to access and remove the bottom cover. The
disassembled CC1 should look as shown in Figure 11. Note how the two halves of the CC1 are
connected through a 2x7 pin header. When reassembling the CC1, be careful to realign these
pins properly.
15
Figure 11. Disassembled CC1
With the bottom cover removed, the programming ports for the RCM3400 and the Cyclone IV
FPGA should be visible and accessible. Using the reverse order, the unit should be
reassembled without the bottom cover. The bottom of the CC1 will look as shown in Figure 12.
Figure 12. Programming ports exposed.
4.2.2 Programming the Rabbit RCM3400
To program the Rabbit RCM3400, a *.bin programming file must first be created in the Dynamic
C 9.62 development environment. To create a *.bin file from Dynamic C source code, select
“Compile -> Compile to .bin file -> Compile to Flash” from the Dynamic C 9.62 program. The
location of this menu option is shown in Figure 13.
RCM3400ProgrammingPort
CycloneIVFPGAProgrammingPort
RemovableBottomCover
16
Figure 13. Creating a programming file for the RCM3400.
With the programming file (.bin) created, plug the USB end of the included Rabbit Programming
Cable (2mm) into your computer’s USB port. The other end of the programming cable contains
two 10-pin headers. The header labeled “PROG” should be connected to the Rabbit
Programming Port on the base of your CC1 unit as shown in Figure 14 (note orientation of red
wire):
Figure 14. Creating a programming file for the RCM3400.
With the Rabbit Programming Cable in place, connect the CC1’s USB cable to your computer -
or to the provided USB power supply - to power up the CC1. Open the DC RFU program that
was installed on your computer. The DC RFU is a programming utility that will use the
programming cable to upload any new firmware files (.bin) to the CC1’s RCM3400.
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Select “File -> Load Flash Image…” from the menu, as shown in Figure 15. Once the proper file
is selected, the uploading of the firmware should begin immediately.
Figure 15. Creating a programming file for the RCM3400.
On some systems, the port location of the Rabbit Programming Cable may not be recognized
automatically. If this happens, you will get an error that says “Could not open serial port.” If this
occurs, you will need to select the “Setup -> Communications…” item in the DC RFU program
menu. This will open up a communications screen where you can select the proper COM port
that identifies your Rabbit Programming Cable. An example of this screen (with the proper COM
port settings) is shown in Figure 16:
Figure 16. Communication settings for the Rabbit Programming Cable.
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