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The "At Last!"
Radio TR Sequencer |
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By:
Bertrand Zauhar, VE2ZAZ
Published
in
the March 2007
issue of ARRL's QST Magazine
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Page last
updated: 06/10/2015

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This
page complements article
"The "At Last!" Radio TR Sequencer" published in
the March 2007
issue of ARRL's
QST
magazine. This page also
provides
updates to the original article.
Please
visit
this page
frequently, and right before assembling the
project, as new information
may get added regularly.
Once again, I
would like to express my
gratitude to Jocelyne, my wife.This project took
6+ months of spare
time to develop, so she
deserves it! Also, thanks to Jim-WB4GCS,
Hugh-VA3TO and Dave-W6TE for
beta-testing this system.
Bert,
VE2ZAZ
ORIGINAL
QST MAGAZINE ARTICLE
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For those
who have not read
the article
yet, this is the best place to start
learning about this project.
Reprinted with permission. Copyright ARRL,
2007 all rights reserved.
This material originally appeared in QST:
Official journal of the ARRL (www.arrl.org/qst).
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OBTAINING
A
PCB AND PROGRAMMMED PIC MICRO
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Note:
As of October 2015, I no longer provide the
blank PCB, as the demand cannot justify a
quantity order of PCBs from my part. Sorry for
the inconvenience.
Please
contact me via email
if you
would like more
information on
the following item described in the article:
- A
pre-programmed PIC 18F2220 micro-controller.
I
will
be happy to provide you with procurement info in
my email reply.
THE LATEST
NEWS, ERRATA AND IMPROVEMENTS
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(Added 29/08/2008)
Optoisolators
Lumex
OCP-PCT124 are no longer stocked by Digikey. You
can substitute
with Fairchild
LTV-814 (Digikey 160-1344-5-ND)
or Sharp PC814XJ0000F (Digikey
425-2439-5-ND).
(Added 31/07/2008)
A
user
reported back that the Firmware Version field
under the Settings
Transfer tab of the Windows Setup tool reports
version "01" even though
the firmware is supposed to
be version "02". I
traced back the problem to
a field I did not update in the PIC program memory
back when I compiled
version 2. Please rest assured, all users received
a version 2 chip.
This is just a display issue. It does not affect
functionality and it
does not call for an increment in the version
number. From here on
though, I will ship version 2 chips that display
"02".
(Added
02/04/2007)
I
added
a note in the Firmware
Programming
section to highlight that the 5V In-Circuit
Serial Programming
(ICSP) is not
supported on the
sequencer PIC firmware load.
(Added 01/04/2007)
The original QST article is now
available for download in PDF form. See above.
(Added
09/03/2007)
Version 1
of the Remote Monitoring tool is now
available for download.
See the software section below.
(Added
02/03/2007)
I am now
shipping version 2 of the PIC
firmware. This
version fixes a small bug in the disarming
process. It also adds remote
monitoring capability. A Windows tool will
allow to
remotely monitor all 6 output LEDs, the PTT
LED and will produce tones.
This saves a lot of wiring for those who
would like to remotely
install the sequencer PCB (tower-mounted,
for example).
I
apreciate reading
back from
experimenters who build this project. This allows
me to
improve this page by providing additional
clarification if necessary.
Thanks!
Due
to space constaints, the top-down view
of the PCB layout was not kept
in the QST article. Here it is for
reference purpose.
Click on the figure to view it in
larger size ->
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CONFIGURATION
SOFTWARE
(WINDOWS)
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This is the
Windows program that provides a user-friendly
interface to the T/R
Sequencer system to configure it. The software
provides the
following
features:
- Microsoft
Windows-based
program
with single window and tabs,
- All
parameters are set up and saved from
within one program,
- Serial
port driven; supports COM1 to COM4,
- Help
provided
via mouse
cursor hints,
- Only
required
at
configuration time.
- Non-invasive
installation; does not
modify the registry nor install DLLs.
All
files
are installed within the same
directory.
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Version 2 of this software must be
used with version 2 of
the PIC firmware (currently shipping).
This
software
was developed and tested in a Windows 98
environment. It was also
tested in Windows 2000 and Windows XP. Since
these operating systems
cover two
main branches of Windows (9x and NT), the
software is expected to run
in all Windows environments from Windows 95
through Windows XP.
REMOTE MONITORING
SOFTWARE (WINDOWS)
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This optional
Windows software provides
the ability to remotely
monitor all 6 output LEDs, the PTT LED and
produces tones through the
PC sound card. This
saves lots of wiring for those who would
like to remotely install
the sequencer PCB (tower-mounted, for
example). The RS-232 link is used
to accomplish this.
- Provides
a
visual indication of Output LEDs and
PTT LED status.
- Provides
sequence
completion tones, a switching alarm
tone and a timeout tone.
- Microsoft
Windows-based
program
with a single small window.
- Serial
port driven; supports COM1 to COM4.
- Non-invasive
installation; does not
modify the registry nor install DLLs.
All
files
are installed within the same
directory.
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For
those of you who would like to
make their own "At
Last!" Sequencer PCB,
here are the top layer,
bottom layer and top
silkscreen layers saved in .PDF format.
The document prints on
Letter-size
paper. When printing in full size (no
scaling), the size and proportions should
be accurate. |
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LEARNING
ABOUT AND
PROGRAMMING THE PIC FIRMWARE
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If
you would like to look at the firmware
load running inside the PIC
micro-controller, well here it is! The
ASM
file is a text file of the source code
I wrote. Beware! This is
Assembly language...The code is well
documented though. Have fun... ;-)
I also provide the latest HEX file
required to upload the
firmware
load into the PIC 18F2220's program
flash. This file is in 8-bit Intel
HEX format, which is the industry
standard for 8-bit micro-controllers.
Note
that 5V
In-Circuit Serial Programming (ICSP)
is not supported on this firmware
load. All pins are assigned
to sequencer functions, so the low
voltage ICSP programming
pins could not be spared for that
task. In order to accomplish the
firmware upload,
you need a PIC programmer
that can handle the PIC 18F series
chips and standard high-voltage
programming.
Version 2 of the firmware supports the
Remote Monitoring feature
through a Windows program. It also fixes
a small bug in the disarming
process. Updated
18/03/2011: I have
updated
the Version 2 files provided
here. There was one small
difference which
I had overlooked. If you tried
to program the PIC with the
previous
files, you may have had
problems, with the PIC not
starting up.
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ADDITIONAL
ASSEMBLY
/ WIRING
INSTRUCTIONS
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- The
7805
voltage regulator should be
mounted with its case "grounded". A
small
TO-220 heatsink should be inserted
between the PCB and the regulator
case. A good example of a suitable
heatsink is Digikey's HS107-ND. A
small bead
of heat-conductive paste should be
applied to both surfaces.
- In-Shack
Wiring. The
figure
to the right shows how the sequencer
must be wired in order to
configure and operate the sequencer
from within the shack.
- RS-232. The RS-232
connection is a
simple 3-wire communication. No
handshaking
or strapping is required at the
PC's end. As well, you do not need
to
set any COM port parameters within
Windows; the software sets these
when data exchange occurs.
- LED
wiring is not clear since
the
PCB does not have
any pin marking showing proper
orientation during soldering. Here
is
how the LED's should be mounted
(also see figure): All
LED's (D3, D6,
D9,
D12, D14, D18, D21) should
have
their green
diode anode
soldered to the square pad. For
Digikey's MV6461A-ND,
this is the longest lead. This
orientation will make the LED's
turn on in green at first power up
(i.e. configuration is still at
default state).
- Remote
Location
Wiring. The figure to
the right
shows
what a typical remote installation
of the "At Last!" TR Sequencer
looks like. It basically uses
(UTP) unshielded twisted pair CAT-5
network cable. The data rate used
by the sequencer is 2400 bps. This
slower rate allows to extend the
cable run without any adverse effect
on transmission quality. I have
made test with 200 feet (60m) of
CAT-5 cable and was amazed on how
little signal quality is affected
with that run. I have every reason
to
believe that we could double that
length and still get good results.
Since this installation is subject
to strong RF exposure, clip-on
ferrite cores can be used at both
ends to reduce EMI pickup. I
obvioulsy cannot provide any
guarantee that the remote setup will
work
under any conditions. The user may
have to experiment with wiring type,
EMI filtering, etc.
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In-Shack
Wiring

Remote
Location Wiring
Click
on
the
figures above to view them in larger
size.
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ADDITIONAL
OPERATING
INSTRUCTIONS
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- Remote
Monitoring
Tool
- In
order for
the sequence tones to be heard through the
sound card and PC speakers,
the sequence tones must be enabled on the
TR Sequencer using the
configuration software.
- The
timeout
tone feature of the remote monitoring tool
is managed by the tool
itself and is totally independent from the
timeout tone setting on the
TR Sequencer.
There are a few more features that are not
documented in the article,
that are worth mentioning here:
- Remote Monitoring
capability. A
Windows tool provides the ability to remotely
monitor all 6 output LEDs, the PTT LED
and will produce tones. This
will save lots of wiring for those who
would like to remotely install
the sequencer PCB (tower-mounted, for
example). The RS-232 link is used
to accomplish this.
- Configuration
Checksum.
In order to make the
re-configuration process
more
robust against noisy RS-232 lines, an
8-bit checksum is calculated when
the Windows software sends the
configuration data to the sequencer. The
PIC firmware calculates its own checksum
based on the data received and
compares it to the received checksum. If
both checksums match, the new
configuration overwrites the old one in
the sequencer, otherwise the
re-configuration does not occur and a
failure message will result in
Windows.
- Auto-Disarm under
a feedback alarm
condition. When an
output
feedback alarm occurs, the sequencer freezes
the outputs in their
current state to allow the user to
troubleshoot the setup and wiring. It will
stay in that frozen
state for a
maximum of 3 minutes, after which the
sequencer will auto-disarm to preserve any
radio equipment that could be transmitting. Of
course, the user can
manuallly disarm the sequencer whenever
appropriate within this 3
minute delay.
- Auto-Disarm when
transmission reaches 11
minutes. When a
transmission (Tx mode) is kept active for 11
minutes
non-stop, the
sequencer will auto-disarm to preserve any
radio equipment that could be transmitting.
This is provided in
addition to the Timeout tone feature and is
seen as a "last resort"
measure.
- Debouncing of the
sequencer PTT. The
sequencer PTT line is debounced in software.
This provides a protection
against fast transitions that could lead to
radio system malfunction.
- Watchdog.
The
micro-controller also has a hardware watchdog
reset feature. In the
unlikely event that the firmware should crash,
the built-in watchdog
will reset the micro-controller. This forces
all outputs to go floating
(open state). The maximum time for the
watchdog to kick in is 4
milliseconds.
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