RigExpert Tokenblauser User manual

RigExpert®
Tokenblauser
User's manual
Low-noise GPSDO,
quad clock source –
0.16 to 200 MHz

Tokenblauser – a versatile GPSDO platform.......................................................4
High stability and low noise...............................................................................6
The first use......................................................................................................7
Menu description...............................................................................................8
Serial port interface..........................................................................................12
Arduino serial plotter.........................................................................................13
TimeLab interfacing...........................................................................................13
Updating the firmware.......................................................................................16
Compiling the firmware from the source code....................................................17
SI5338 configuration presets............................................................................17
Annex 1 – Specifications...................................................................................18
Annex 2 – Glossary...........................................................................................19
Table of contents

44 User's manual
The Tokenblauser is a GPS disciplined clock source with very low noise output,
suitable for QO-100 and SHF applications, including operating FT8 and other
narrow band digital modes. Unlike many other GPSDOs with fixed 10 MHz output,
it additionally generates up to four arbitrary frequencies simultaneously. This
functionality is provided “out of the box” and does now require advanced skills
from the user. Just apply power to the device and connect a GPS antenna, then
enter or change output frequencies.
Tokenblauser –
a versatile GPSDO
platform
Example of use for operating the QO-100 satellite

Tokenblauser 5
However, we designed the Tokenblauser to be also a versatile platform for
experimenters. The device is Arduino-compatible, and the firmware is open-source.
With no or minimal changes in the code or in the hardware, an advanced user may:
• Connect the GPSDO to a computer for debug purposes or data processing
(such as plotting ADEV/MDEV graphs);
• Modify the firmware to experiment with different PLL and FLL algorithms;
• Use own GPS modules and GPS antennas;
• Use different types of OCXOs and Rubidium oscillators.
Structure diagram of the Tokenblauser GPSDO
The Tokenblauser is based on ideas of Brooks Shera, Lars Walenius and many
other enthusiasts.

66 User's manual
Just look at a simplified Allan
deviation chart, which compares the
stability of different types of
generators over time. The GPS receiver
itself has a bad short-term stability,
where the OCXO is good. In opposite, during long periods, the GPS is a winner.
The next chart is one of
standard models of an
oscillator phase noise.
Obviously, for a better GPSDO,
the corner frequencies fc1 and
fc2 need to be located as close to
the carrier frequency as possible.
If the GPSDO output is
multiplied by the PLL-based
oscillator, we usually think of 20
High stability
and low noise
By locking the frequency of a
local oscillator to the reference
GPS receiver, GPSDOs are
capable to have good stability
in both short-term and long-
term areas. The position of the
intersection point depends on the
type and the quality of oscillator
used; for OCXOs, it is usually 100
to 1000 seconds. Thus, OCXO-
based GPSDOs are able to provide
good frequency stability for
laboratory and hobby use.
dB/decade as a noise increment. However, this is not an axiom: much more noise
is added for frequencies to the left of fc1. By using a professional-grade OCXO, as
well as carefully designing the RF circuits, very good noise parameters of the
GPSDO can be achieved.

Tokenblauser 7
Connect the GPS antenna and
locate it in such a way, that at least ½
of the sky is visible. It is always better
to locate the antenna outdoors,
whenever possible.
Connect it to 9-15V power supply.
Once the power is turned on, the red
LED on the front panel starts flashing: the GPS module is now searching for the
satellites to synchronize time.
The first use
Once the satellites are discovered, the GPSDO starts the locking process. The
green LED is now flashing. Be patient, this may take several minutes.
Once the output frequency is stable for the last 100 seconds, the GPSDO
indicates a locked status. The green LED on the front panel now stops flashing.
In addition to the locked status, the OLED shows the time since the last lock
event, and the average signal level of the received GNSS satellites. Adjust the
position of your antenna for the highest signal level:
<20 dBHz = poor, 20..25 dBHz = good, >25 dBHz = excellent.
Buttons
Press ⊖ or ⊕ button shortly to browse through the menu. Hold these buttons
for approximately two seconds to change current profile number, set output
frequencies or to enter Preferences. Press the M (Menu) button to exit back to
the Status screen.

88 User's manual
Setting output frequencies
To change profile number, press ⊖ or ⊕
button to select the Profile menu item, then hold
one of these buttons for approximately two seconds
to change the profile number.
For each of four profiles, you may change
frequencies for each of A…D outputs. With ⊖ or
⊕ button, select the desired output, and then hold
one these buttons to edit its frequency.
Menu description
An editable digit starts flashing. Short press ⊖
or ⊕ to select the digit to edit, or hold one of these
buttons to increment or decrement the selected
digit. Please make sure that the desired frequency is
inside the specifications of this GPSDO.
Press Menu to exit the editor mode.
Preferences
Select Prefs from the top menu, then hold ⊖ or
⊕ to enter the Preferences menu. Experienced
users may tweak several parameters of the GPSDO
here.
Checking the OCXO center frequency
First, use the SetDACcen menu to set the DAC
to its center value (32768).
Notice the value of the dt while in Hold mode. If
the value if out of the ±100 ns range, adjust the potentiometer (if installed) on the
printed circuit board to set is as close to zero as possible.

Tokenblauser 9
OCXO tuning range settings
To set the maximum tuning range of the OCXO,
select Range and hold ⊖ or ⊕ to change. The
tuning range is set in ppt (parts per trillion). It is
necessary to set the tuning range properly for the
algorithms to work correctly.
The OCXO tuning range is defined as a relative frequency change of the OCXO
when the DAC changes its value to from its minimum to its maximum. Use
SetDACmin and SetDACmax menus to control the DAC.
Hold ⊖ or ⊕ to set the 16-bit DAC in its
minimum (0) and then maximum (65535) value.
After applying this setting, the GPSDO will enter
the Hold mode, returning to the Status screen.
Notice the value of the dt while in Hold mode.
The value shows how much the output the 1PPS output of the GPS is ahead or
behind of the pulses of the internal OCXO. Positive values mean that the frequency
of the OCXO is lower than 10 MHz, and negative values mean higher OCXO
frequencies.
To find out the exact tuning range of the OCXO installed in your GPSDO, follow
this algorithm:
1) Set the DAC to its minimum value by using the SetDACmin menu. Write
down the dt value, such as 241ns.
2) By using the SetDACmax menu, choose maximum value. Again, write
down the dt value. Example: -240 ns.

1010 User's manual
With the above example, the tuning range of the OCXO (limited by resistor
network inside the GPSDO) is
241 + 240 = 481 ppb (parts per billion) -or- 481000 ppt (parts per trillion)
Enter the value 481000 ppt in the Range menu, for the PLL algorithm to work
properly. For OCXOs with negative control voltage characteristic, the Range value
will be negative.
Positive and negative control voltage characteristics
PLL settings
By using the Prefilter time constant, the Loop filter time constant and the
Damping factor menus, parameters of the phase locked loop may be tweaked, as
illustrated by the picture below.
Example loop filter settings: 100 sec – faster locking, less stable output (10–9).
500 sec – slower locking, more stable output (10–10).
Prefilter and PI-loop filter

Tokenblauser 11
Hold and Run modes
By activating the Hold menu, the phase locked loop algorithm is deactivated
and the DAC holds voltage to control the OCXO.
The Run menu gets the phase locked loop back to normal operation.
GPS settings
The Init GPS menu is responsible for re-initializing the GPS module every time
the GPSDO is turned on (default: YES). For various experiments, you may choose
NO.
The Communication mode defines the behaviour of the virtual COM port. The
Command line is a normal operation mode of the GPSDO. The GPS mode creates
a transparent connection between the GPS module and the virtual COM port. Use
this mode to be able to control your GPS module directly by specialized software,
such as u-center or Lady Heather.
Other settings
Display – select either Bright (default) or Dark mode.
Run boot loader – enter the boot loader mode for firmware update (see
below).
Factory reset – revert to default settings.
SI5338 menu – display the device grade and maximum output frequency.
FW ver. – show current firmware version.

1212 User's manual
The virtual serial port interface
provides various functions, such as
control or monitoring of the GPSDO.
Open a virtual serial port (for example,
COM22) with terminal software, such
as Putty or Arduino IDE.
Type “?” or “help” to get a list of
available commands, as well as current settings of the device. The serial interface
is self-documenting. Most commands are available through the front-panel menu of
the GPSDO.
Serial port
interface
hold  stop PLL
run  run PLL
dac<N>  set DAC output to value N=0...65535 in hold mode
savedac  save current DAC value
readdac  read saved DAC
trans  enter GPS transparent mode, +++ to exit
pre<N>  set prefilter time constant to N seconds, or 0 to
disable prefilter
loop<N>  set loop time constant to N seconds
damping<N>  set loop damping to N (0.5 to 10)
range<N>  set OCXO tuning range (in ppt) to N
saw<N>  set sawtooth correction to 1 (on) or 0 (off)
initgps<N>  init GPS at startup: 1 (on) or 0 (off), initgps to
reinit
offset<N>  set frequency offset (in ppt)
ss  take a screenshot, ss<char> to use <char> instead of bricks
verb<N>  set verbose level to 0 (min) or 1 (max)
legend or <CR>  print legend
restart  restart the device
boot  jump to bootloader
When the 1PPS signal is available from the GPS module, a row of numbers is
output every second:
rawps qErrps corrps preps 1ppsps dac_val
6142 5995 147 2279 347 23915
4723 3698 1025 2237 878 23915
2951 1392 1559 2215 534 23915
raw-ps – raw output of the time interval counter (TIC); qErr-ps – quantization
error value read from the GPS module; corr-ps – corrected TIC value; pre-ps –
prefilter output; 1pps-ps – phase difference between 1PPS pulses; dac_val –
current DAC value.

Tokenblauser 13
To be able to tweak PLL parameters on the fly, first enter the verb0
command.
Arduino serial plotter
By using the Serial plotter function of the Arduino IDE, you may visualize the
behavior of the phase locked loop.
Open Tools – Serial plotter (or press Ctrl-Shift-L), then type legend in the input
window and click Send (or just click Send without typing anything).
TimeLab interfacing
With the famous Timelab software from Miles Design LLC., plotting Allan
deviation of the internal TIC is made easy. The real-time mode is activated by
clicking the Acquire – Acquire from counter in Talk-Only mode.
To plot the phase data, select Phase difference, then enter Numeric Field
#3 (corrected TIC value) and set the phase multiplier to 1e-12.

1414 User's manual
A sample of Allan deviation plot for the phase data
TimeLab interfacing
With the famous Timelab software from Miles Design LLC., plotting Allan
deviation of the internal TIC is made easy. The real-time mode is activated by
clicking the Acquire – Acquire from counter in Talk-Only mode.
To plot the phase data, select Phase difference, then enter Numeric Field
#3 (corrected TIC value) and set the phase multiplier to 1e-12.
Click Start Measurement.

Tokenblauser 15
A sample plot of the Frequency Difference
To plot the frequency data, select Frequency difference, then enter Numeric
Field # 6 (DAC value) and set the frequency multiplier. The multiplier as calculated
as:
(OCXO tuning range in ppt)/65536*10-12
For instance, for the tuning range of 847000 ppt, enter 12.9e-12.
Click Start Measurement.

1616 User's manual
Updating the firmware
To update the firmware by using binary file, install the BOSSA programmer
from https://github.com/shumatech/BOSSA/releases . Run the program.
Important: enter 0x2000 in the Flash Offset field. Please do not touch any
check boxes; else, your GPSDO may be bricked!
Browse for the new firmware file.
Put the GPSDO into the boot loader mode: either use the Run boot loader
menu from Preferences, send the boot command via the virtual serial port, or
double-press the RESET button (if installed) at the PCB.
In the BOSSA dialog, click Refresh and choose an available Serial port number.
Click Write to start programming. Reset or re-plug the GPSDO after finishing
the programming process.

Tokenblauser 17
Compiling the firmware from source code
To be able to modify and re-compile the firmware, make sure to:
1) Install the latest version of the Arduino environment from
www.arduino.cc .
2) Open the Boards Manager from Tools – Board – Boards Manager menu.
Install the Arduino SAMD Boards (32-bits ARM Cortex-M0+).
3) Open Library Manager from Tools – Manage Libraries menu, and then
install the following libraries:
SAMD_TimerInterrupt
FlashStorage_SAMD
Adafruit_SSD1306
Adafruit_GFX_Library
TDC7200 library: https://github.com/Yveaux/TDC7200
4) Select Arduino Zero (Native USB Port) from Tools – Board - Arduino
SAMD Boards menu.
5) Select the corresponding COM port number.
SI5338 configuration presets
For making initial C code header configuration files for the SI5338 frequency
synthersizer chip, use Skyworks ClockBuilder Pro software, see https://
www.skyworksinc.com/en/application-pages/clockbuilder-pro-software .
Export the register file to Si5338-RevB-Registers-X.h , where X=1..4 (profile
number).

1818 User's manual
Power supply: 9-15V, 1A max.
USB interface: USB 2.0, type B
connector (dvice is not powered from
USB); Virtual serial port compatible
with Windows, Mac OS and Linux
GPS input: 3V active antenna with SMA connector; hardware modifiable for
5V antennas; reception of GPS, Galileo and BeiDou GNSS
Frequency stability: 10–9...10–10, depending on GPSDO settings, antenna
location and satellite signal levels
Reference clock: One 10 MHz output (BNC); 3.3V CMOS levels, hardware
modifiable for sinewave output; hardware modifiable for 5V CMOS levels
Arbitrary frequency clocks: Four outputs - A,B,C,D (BNC); independent
frequency entry, 0.16 to 200 MHz in 1 Hz steps; 3.3V CMOS levels; hardware/
software modifiable for LVPECL/LVDS/HCSL/CMOS/SSTL/HSTL levels
User interface: 0.91” monochrome OLED; three front panel buttons; four
frequency profiles for fast switching of output frequencies
Software compatibility: Arduino SAMD21 compatible; serial plotter
supported in Arduino environment; debug output which can be analyzer by
TimeLab and other software; transparent mode for direct access to the GPS
module
Dimensions: Enclosure: 105x105x35 mm; PCB: 100x100x25 mm
Experimenter’s corner: Tweak parameters of the GPSDO from the front
panel; modify the firmware and upload to the device by using Arduino
environment; use GPSDOs PCB as a module for your own device; replace built-in
GPS module with external one; replace built-in OCXO with own OCXOs
(rectangular or sinewave output) or Rubidium oscillator. Typical extended
frequency range (not guaranteed): 40 kHz to 710 MHz (SI5338 grades A,D,G,K,N),
to 350 MHz (grades B,E,H,L,P), to 200 MHz (grades C,F,J,M,Q).
Recycled/refurbished materials: OCXO
Specifications are subject to change without notice.
Annex 1
Specifications

Tokenblauser 19
1PPS – One Pulse Per Second
ADEV – Allan Deviation
Arduino – popular hardware and
software platform, including
development environment
DAC – Digital-to-Analog Converter
(for a 16-bit DAC, the min value is 0
and the max value is 65535)
FW – Firmware
GPS – Global Positioning System (other navigation systems, such as Galileo
and BeiDou, are also often called GPS)
GPS module – hardware module containing specialized processor
GPSDO – GPS Discipline Oscillator
HOLD mode – mode of ther GPSDO, when the PLL is not allowed to control
the DAC
Lars GPSDO – original Arduino-based GPSDO design by Lars Walenius
MDEV – Modified Allan Deviation
OCXO – Oven Controlled Xtal (Crystal) Oscillator (usually, voltage controlled)
OCXO Tuning Range – typically, +-1…3 ppm in reaction to a full swing of
control voltage
OCXO Tuning Range Limiting – a technique to limit the tuning range by
resistor network
PLL – Phase Locked Loop
PPB – Part Per Billion (1e-9, example: 0.01 Hz at 10 MHz)
PPM – Part Per Million (1e-6, example: 10 Hz at 10 MHz)
PPT – Part Per Trillion (1e-12, example: 0.00001 Hz at 10 MHz)
qErr – quantization error of 1PPS; the data to correct this error, sent from a
GPS module via UBX
RUN mode – the PLL is allowed to control the DAC
Sawtooth correction – software algorithm to combine TIC result with data
read from a GPS module
TIC – Time Interval Counter
TimeLab – software for precision time and frequency measurement by Miles
Design LLC.
UBX – proprietary data exchange protocol of u-blox
Annex 2
Glossary

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Doc.date: 07-Aug-2022
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