How To Build “Megavolt’s Small Buffered JTAG
v1.2”
Abstract “A JTAG cable should be considered mandatory equipment for any serious
tester. It provides a means to backup the information in the receiver and restore it
whenever necessary. This document illustrates the process of building one that is safe to
use in any receiver.”
An illustrated guide by DO999
Revised August 20th , 2002
Version 1.01
DO999 @ www.dssword.com
or
DO999 @ www.sattech.net
Preface................................................................................................................................. 1
Introduction......................................................................................................................... 1
Assumptions........................................................................................................................ 1
Electrical Schematic by SatFTA......................................................................................... 4
Construction – General ....................................................................................................... 5
Construction of the JTAG module ................................................................................. 5
Step 1: Initial assembly of the PCB. ........................................................................... 5
Step 2: Mount (solder) the main components ............................................................. 6
Step 3: Connect the parts together. ............................................................................. 7
Step 4: Add the single 100 Ohm resisitors.................................................................. 8
Step 5: Creating a grounding strip .............................................................................. 9
Step 6: Connect wire for Vcc (power) and Ground to the circuit ............................... 9
Step 7: IRD JTAG Port Connection.......................................................................... 10
Step 8: Computer (PC) Connection .......................................................................... 11
Step 9: Completion of JTAG module. ...................................................................... 12
Installation......................................................................................................................... 13
Installation - PC Connection......................................................................................... 13
Mounting the DB25 .................................................................................................. 14
Installation - Connecting to the IRD............................................................................. 14
Installation - Power Connection.................................................................................... 15
Optional PAD 1 Grounding Switch.............................................................................. 15
Installation – Internal Mounting ................................................................................... 16
Conclusion ........................................................................................................................ 16
Troubleshooting ................................................................................................................ 16
Appendix A – Images ....................................................................................................... 17
Internal JTAG for a 3100 .............................................................................................. 17
Standalone JTAG that can be used on any IRD............................................................ 18
IRD JTAG Connection Images ..................................................................................... 19
Model 2700 ............................................................................................................... 19
Model 3100 / 301 ...................................................................................................... 19
Model 5100 / 501 ...................................................................................................... 21
Model 6000 ............................................................................................................... 21
Appendix B – Detailed Parts List ..................................................................................... 22
Preface
The first thing I want to point out is that this guide is nothing more than an assembly
guide. The credit for the actual circuit design goes to SatFTA. These instructions expand
on the “Megavolt’s Small Buffered JTAG v1.2” documents by adding step-by-step
pictures and some alternative construction techniques. All the real credit belongs to those
SatFTA and MegaVolt.
Second, I want to mention that the document is fairly long but hopefully that is due to the
level of detail I am putting into it. This project really is fairly simple to construct. Many
sections will not apply to you and the JTAG that you will build. You should of course
read the entire document before starting construction. This will allow you to ge t the
necessary parts and have a good understanding of the options available to you.
Introduction
Megavolt set out to create a buffered JTAG without a Printed Circuit Board (PCB), small
enough to fit inside a DB25 housing. He was quite successful and the design was
brilliantly simple. This guide expands on that by adding in the PCB such that it can be
mounted inside the IRD case or a small project box. Examples, information and pictures
of various optional parts and mounting techniques will be shown later in this guide.
Assumptions
It is assumed that the reader has a basic level of soldering skill. The construction is fairly
straightforward and with the PCB a beginner should be able to accomplish the task.
Knowledge and understanding of electrical diagrams is not required even though they are
included in the guide.
It is also assumed that you have read Megavolts documents as they provide some details
and background that I do not. Some of the information presented here is directly from
that document.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 1
Purpose
In general, the purpose of any JTAG cable (buffered or not) is to read and write the TSOP
chip within the receiver (IRD). The most common reason for using the JTAG is to extract
the BoxKey information from the IRD. Once you have the BoxKeys, you are able to test
options that do not require the use of the smartcard (CAM) such as the Atmega128 or
computer emulation software. This connection also allows you to create backup images
of the firmware within the unit. The firmware is the program code that basically makes
the unit work. It is the equivalent to the operating system that you load onto a computer.
Being able to read / write the firmware is important to recover from ECM’s or to ‘roll
back’ the firmware to a previous version that may not have ant i-testing ‘features’ in it
(like firmware version E338 on the 3100 IRD). In addition, with great software like
JKeys by Dave2 you cannot only backup the TSOP (or TSOPs since x100 series IRDs
have more than one chip) but you can also read and write the EEPROM chip through the
same cable and software. (Note: Wall version 2 also works great on the 3100)
If you have read this far you probably already know why you want to build a buffered
JTAG. Just in case, the brief rundown is that the buffered JTAG supplies data signals and
voltages that are friendly to both the IRD (receiver) and the computer. The simple resistor
style JTAG can use in excess of 5V which is greater than the 3.3V used in the TSOP the
x100 series IRD and not only can it result in poor reads / writes but it can significantly
damage the TSOP. This is not to say that it will absolutely happen, just that it could. The
use of a buffered JTAG alleviates these issues. The resistor style JTAG (which I won’t
get into here) is great on the x700 (and I’m sure other types) series IRD. Personally, I had
nothing but troubles with the simple JTAG on a 3100 and that is when I was ‘converted’
and jumped on the buffered JTAG bandwagon.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 2
Parts List
A detailed parts list, with pictures, is included in the appendix to this document. Part
numbers, approximate cost and supplier information can also be found in the appendix.
In summary, the following parts will be used:
Quantity
1
1
2
2
1
1
1
1 (Optional)
1 (Optional)
1 (Optional)
1 (Optional)
1 (Optional)
1 (Optional)
6 (Optional)
1
1 (Optional)
Description
74HCT244 Octal 3-state noninverting line receiver chip
2.2K Ohm Bussed 9 resistor network (10 pin Single Inline Package[SIP])
100 Ohm Isolated 4 resistor network (8 pin SIP)
100 Ohm resistor
Printed Circuit Board (PCB)
DB25 Connector – Male or Female depending on your PC parallel cable
6” strip of 6 or 10 conductor ribbon wire. (An old floppy cable works
well.)
DB25 housing – Used if you are not mounting the JTAG inside the IRD
SPDT or SPST switch – Used for Power On/Off
SPDT or SPST switch – used to ground Pad 1 on some IRD’s. Also a
momentary contact switch (push button) works well for this.
20-pin socket to mount the 74244 chip not required if you solder the chip
directly to the PCB
SIP socket strip with 26 pins not required if you solder the resistor
networks directly to the PCB
Plastic project box required if you are making a portable, external JTAG
Pogo / Spring pins to connect to IRD JTAG port. Not required for
directly soldered cabling.
Miscellaneous length of wire, solder, glue or other mounting material
3.3V (3.0V to 3.6V) power source. Battery or transformer. Not required
for internally mounted JTAG. [2 x AA batteries for an x100 series or 3 x
AA batteries for a x700 series IRD work well]
An internally mounted JTAG using only the mandatory items listed above will run about
$10-$15 Canadian. Obviously, the more optional parts that are used, the higher the cost.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 3
Electrical Schematic by SatFTA
Here is the overall design of what we are trying to make. If you can follow the directions,
it is not necessary to understand this drawing.
A simplified drawing mapped onto the board layout would look like this:
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 4
Construction – General
The Buffered JTAG consists of the PCB with the various resistors and 74244 chip
mounted on it. The connection to the PC DB25, the JTAG port and power will be
described as part of the Installation process.
Construction of the JTAG module
Once again I want to emphasize that these steps are essentially the same as those
published by Megavolt with the addition of a PCB. I also chose to build the JTAG using
sockets for the components because that is the way I was taught and the pictures are
easier to view with them. It is also easier to replace the parts or borrow them for other
projects. The main reason for using sockets is to prevent damage to the components from
over heating during soldering. Sockets are not required and add to the overall cost of the
project. Feel free not to use them.
Step 1: Initial assembly of the PCB.
Trim (ie cut) legs (pins) 2, 3, 5, 7 & 9 off the 2.2K Ohm resistor network or the SIP
socket as shown below. These pins are not required and will get in the way later if not
removed. Note that Pin 1 of the resistor network is typically on the left side when
viewing the side with printing on it and should be marked with a coloured band or other
indicator such as a dot or triangle.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 5
Step 2: Mount (solder) the main components
Start by placing the 74244 chip or the 20-pin socket in the middle of the PCB to allow for
other components to be located around the chip. Align the resistor networks or SIP
sockets as indicated in the picture. Note the resistor networks/SIP sockets should be
mounted right beside the 74244 chip or 20-pin socket and not as shown. The image
simply shows the alignment. See the next image for actual placement.
The image below shows the correct placement of the chips / sockets as viewed from the
top of the PCB.
On the back side of the PCB, solder all pins to the connection points on the PCB but do
not bridge solder between any of the pins at this time. There should be 20 solder
connections for the 20-pin socket, 5 solder connections for the 10-pin SIP socket (2.2K
resistor network) and 8 solder connections for each of the two 8-pin SIP sockets (100
Ohm resistor networks).
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 6
Only 5 connection are required for the 2.2K Ohm resistor network because you removed
the other unused pins.
Step 3: Connect the parts together.
Use solder on the back side of the PCB to bridge a circuit between pins 1, 4, 6, 8, 10 of
the 2.2K Ohm bussed resistor network and pins 20, 17, 15, 13, 11 of 7444 chip or socket
respectively as indicated in yellow below. ie Pin 1 of the resistor network connects to pin
20 of the 74244, pin 4 to pin 17 and so on.
Using the same technique extend the solder from pins 4, 6, 8, 10 of 2.2K Ohm resistor
network to the adjacent pins (1, 3, 5, 7) of the 100 Ohm resistor network creating a
connection across all 3 pins.
On the other side of the 74244 chip connect pins 3, 5, 7, 9 to pins 1, 3, 5, 7 of the second
100 Ohm resistor network.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 7
Step 4: Add the single 100 Ohm resisitors.
Solder a 100 Ohm resistor to pin 2 of the 74244 chip and a second 100 Ohm resistor to
pin 18 of the 74244 chip.
Note: When installing the resistor connected to pin 18, leave the wire (lead) on the
resistor fairly long as you will connect it past the 2.2K resistor network as shown below.
Once it is in place, trim the excess wire off with a pair of cutters.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 8
Step 5: Creating a grounding strip
Connect pins 1, 4, 6, 8, 10, 19 of 74244 chip together to form a common grounding point.
Use a piece of solid wire and solder it between the pins listed. Make sure the wire does
not come in contact with anything else. I left the ground wire long in the image in case I
wanted to use it later in the construction process.
Step 6: Connect wire for Vcc (power) and Ground to the circuit
In preparation for connecting power to the circuit, add a red (Vcc) and black (ground)
wire (or any colo ur) connecting Vcc to pin 20 of the 74244 chip and the ground to pin 1
or the grounding strip created in the previous step.
Optionally, the Vcc line can be connected to a power switch if you are using a battery so
that the circuit can be powered off to the save the life of the battery when not required.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 9
Step 7: IRD JTAG Port Connection
A 6-wire or 10-wire ribbon cable can be used to connect to the JTAG port on the IRD.
This may be soldered directly to the IRD or may be connected via the optional pogo pins.
Ultimately, you want this portion or the circuit to be as short as possible. For now, ensure
that you will have plenty to work with as you can easily make it shorter later on. If using
a 10-wire ribbon cable, connect every second wire to the ground line (not shown). By
grounding every second wire you are in effect isolating the signals in the ribbon cable
and reducing any ‘noise’ picked up by the wiring. This makes the signal cleaner and
reduces the potential for problem reads or writes.
Connect one wire to the grounding strip, four wires one to each of pin 2, 4, 6 & 8 of the
100 Ohm resistor network and the 6th wire to the single 100 Ohm resistor.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 10
Step 8: Computer (PC) Connection
Similarly on the other side of the chip you need to connect a cable (such as Cat 5 network
cable) to the circuit. A DB25 connection will be installed later and this will be connected
to the parallel port on your computer.
Connect one wire to pin 19 of the 74244 chip, one wire to the 100 Ohm resistor and the
remaining 4 wires to pins 2, 4, 6 & 8 of the 100 Ohm resistor network as indicated.
Note, when connecting to pin 19 of the 74244 chip, skip over the contact for the 2.2K
Ohm resistor network. You should have cut that pin off at the beginning so it will not be
a problem. You may alternatively connect this wire to any other convenient grounding
point.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 11
Step 9: Completion of JTAG module.
If you used sockets, you may now insert the 3 resistor networks and the 74244 chip. This
marks the end of the basic module construction. All that is left is to connect it up.
Trim the PCB and mount it inside the project box if one is going to be used.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 12
Installation
Installation - PC Connection
A DB25 connector (25-pin) is used to interface to the computer as mentio ned previously.
This connection will plug into the parallel port on the computer. If you already have a
cable on this port then the easiest thing to do is install the corresponding DB25 connector.
For example, I have a 25-pin male-to-female straight through cable attached to my
parallel port already so I wanted a male DB25 for it to plug in to.
There are different types of DB25 connectors. The simplest one is a solder type where
you solder the wires onto terminals in the DB25. I used a crimp connector type for mine
since I had the parts and crimper tool handy. That is what you will see in the pictures.
As indicated below, you need to connect the wires from pins 8, 6, 4 & 2 of the 100 Ohm
resistor network to corresponding pins 2, 3, 4, & 5 of the DB 25 connector. Additionally,
connect the 100 Ohm resistor to pin 13 of the DB25 and connect a ground wire to pin 25
of the DB25.
Important Note: If you need to pass the wiring through a hole in the IRD, the project box
or anything else, do so before connecting the DB25.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 13
Mounting the DB25
If you are making a stand alone JTAG that will be used on more than one IRD then you
probably want to mount the PCB inside a small plastic project box. You could mount the
DB25 directly into the wall of the box or drill a hole for a wire and put the DB25 into a
housing that you can purchase for a professional look.
Similarly, if you are mounting the JTAG inside an IRD you can mount the DB25 in a slot
cut into the casing of the IRD or drill a hole to pass the wire through the case and put a
housing over the DB25. Cutting a slot for the DB25 in the IRD case can be difficult.
Installation - Connecting to the IRD
Connecting the ribbon cable to the JTAG port on the IRD can be tricky because not all
IRD’s have the same configuration and the pinout may change between revisions.
However, the basic concept remains the same. You need to connect the ribbon cable to
the TMS, TCK, TDI, TDO, nTRST and Ground lines of the IRD.
The following chart has been included (thanks to SatFTA) but you should check for a
newer version on the internet if your specific model is not included.
Additionally, there are a number of ways to connect the ribbon cable to the JTAG port. I
built a buffered JTAG that I can use on any IRD (that has a port) by connecting the
ribbon cable to pogo pins. This is similar to the commercial ones that you can purchase.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 14
My prototype was built using the connector from a commercial JTAG, I simply cut the
ribbon cable and connected it to my circuit.
The second one I built from scratch. I marked the position of the JTAG pads on a piece of
paper and drilled holes into a piece of wood that the pogo pins could fit into. I then used a
hot glue gun to build up a block of glue around the pins, which I could shape with a knife
and the glue gun. It fits perfectly into the existing opening in the IRD.
The 3100 (and 5100) take considerably longer to read / write than the 2700 I started on so
I decided to mount a JTAG into the 3100 on a permanent basis. This one I wired directly
to the top of the motherboard and I cut a slot into the back casing for the DB25.
This section may seem a little vague, but I will leave it up to you to decide how you will
connect to the IRD. Pogo pins and direct wiring both have advantages and disadvantages.
Installation - Power Connection
The 74244 chip requires power for the circuit to function. If you are building an external
JTAG then the use of a battery or power transformer is necessary. In the two external
types that I built I used a 3.5V lithium battery. I installed a switch so that I could power
on the circuit only when required to save battery life. If you use a transformer, simply
unplug the transformer to cut power, no switch required.
On the internally mounted JTAG I found a 3.3V connection on the motherboard (positive
(+) side of a capacitor) that I used to power the circuit. I did not see the need for a power
switch since powering the circuit should not affect normal operation of the IRD. I
connected to capacitor C137 but there are a number of available connection points. A
ground point is easy to find. Connect to the side of the casing if you are in doubt
Voltages between the range of 3.0V and 3.6V should be fine for the circuit to function
normally.
Optional PAD 1 Grounding Switch
A switch can be used to created a ground connection for Pad 1 on the x700 series IRD’s.
If the switch is used (on) when A/C power is applied the IRD boots up into a service
mode permitting writes to the TSOP. This is particularly useful for internally mounted
JTAGS.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 15
Installation – Internal Mounting
If you are installing the module internally, you can use the same type of plastic standoff
that is used to mount a motherboard for a computer into a case. A local computer store
will probably provide you with a couple at minimal or no cost. Simply trim the plastic
tabs to make a flat foot for the module to sit on.
Use cable ties to secure the wires to the module and the case. You don’t want them lose
inside the IRD.
Conclusion
Now that the JTAG is built and installed, grab a copy of JKEYS (version 2.01 is current
as of the time this document was prepared). Grab your BoxKeys and a backup of your
TSOPs and EEPROM. You will be able to sleep better at night knowing you can restore
these whenever necessary.
Troubleshooting
An
excellent
troubleshooting
guide
can
be
found
at
http://www.kickinchicken.org/phpBB2/viewtopic.php?t=445 . I hope this link stays
active for a while.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 16
Appendix A – Images
Internal JTAG for a 3100
The following image shows the mounting and connection points (in general) of the JTAG
built to connect to the top of the 3100 motherboard and using a slot cut in the case for the
DB25 PC connection.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 17
Standalone JTAG that can be used on any IRD
This image shows a battery powered JTAG with pogo pins that can be used on any IRD
that has a standard JTAG port.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 18
IRD JTAG Connection Images
The following images show the Pad configuration for a number of IRDs.
Model 2700
Note: The 2 images have reversed front / back from each other.
Model 3100 / 301
The 3100 has a number of different pin configurations so match the image to your IRD.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 19
It is also possible to connect to the inside of the 3100 IRD on the top of the motherboard
at the EJTAG port. Note that the connection configuration is completely different from
the underside connections.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 20
Model 5100 / 501
Model 6000
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 21
Appendix B – Detailed Parts List
Most of the parts can be found at an electronic store or on the Internet at www.digikey.ca.
The PCB is a Radio Shack part and the Pogo pins were obtained from
www.solarbotics.com.
Detailed Parts List
Qty
Description
1
74HCT244 Chip
Image
Part No: SN74HCT244N
Alternate Parts:
74HC244
Cost: $1.99
1
2.2K Ohm Bussed 9
resistor network (10 pin
SIP)
Part No: 4610X-101-222
(2 per package)
Cost: $1.49 per package
2
100 Ohm Isolated 4
resistor network (8 pin
SIP)
Part No: 4608X-102-101
(4 per package)
Cost: $1.49 per package
2
100 Ohm resistors
Part No: 1/4W-100R-5
(5 per package)
Cost: $1.49 per package
1
Alternate Part: 1/2W
resistor as shown.
3.3V Power Source
(Optional)
Battery or Transformer
2 x AA batteries (3.0V) or 3 x AA batteries (4.5V) can also be used.
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 22
Qty
6
Description
Pogo (Spring) Pins
(Optional)
Image
Part No: PP3
Alternate Parts: Other style
pogo pins
Cost: $0.90
Total Cost: $5.40
1
DB25 25-pin connector
Part No: (Don’t know, had
some already)
Alternate Part: Crimp style
instead of solder style.
1
Cost: $3.50 (Approx)
DB25 Shell
(Optional)
Part No: (Don’t know, had
some already)
Cost: $3.50 (Approx)
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 23
Qty
2
Description
SPDT Switch (Optional)
Image
Part No: 35-001
Cost: $5.49 Each
Total Cost: $10.98
1
20-pin Socket for
74HCT244 (Optional)
Part No: DM-320STG30CF
Alternate Parts:
Open frame low-profile
Cost: $2.99
1
SIP Socket strip for
resistor networks
(Optional)
Part No: SIP64S-TG30
Cost: $4.99
1
Project Box (Optional)
Part No: K-JM12-IE-000
Alternate Parts: Any small
project box
Cost: $2.99
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 24
Qty
1
Description
Circuit Board
Image
Part No: 276-148A (2 per
package)
Alternate Parts: Any small
project board
Cost: $3.49 (Approx)
How to build “Megavolt’s Small Buffered JTAG v1.2” by DO999
Page 25