Building a JTAG Interface

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Revision as of 16:13, 6 July 2006 by Dtaylor (Talk) (Attach the IDE connector Cable)

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There is a possibility that you could brick your NAS with these instructions. Please make sure that you read the entire page carefully. Adding a JTAG header to the Kuro requires soldering onto the Kurobox main board and can cause catastrophic failure to the hardware, Of course, there is also the distinct possibility that you need a JTAG cable because you have already bricked your Kuro. In that case, I wouldn't worry too much about damaging your Kuro.

Building a JTAG interface cable can be accomplished in part of an evening by following these instructions. I have built 10 of these and assembled 12 kits with all parts and an etched predrilled circuit board which we are making available to the community in an effort to spur more development (sounds like a contest entry). There is a thread in the Forums for discussion and announcememnts regarding the availability of these kits. If you are interested in assembling and distributing kits or have any assembly questions, please post a note in the forum thread. If not, then I must assume you are here to assemble you kit, so lets get started.

Parts Required

In order to build one of these you will need the following parts:

Tag Description Quantity Mouser Part Number Comment
R1 100 ohm 1/8 watt resistor 5 270-100-RC First 4 of 5 tripes are Brown Black Black Brown
R2 2.2 K 1/8 watt resistor 4 270-2.2K-RC First 4 of 5 tripes are Red Red Black Brown
C1 0.1uF tantalum capacitor 1 80-T350A104K035 -
IC1 Quad Buffer 1 511-M74HC125 -
Conn1 16 pin wire mount IDC socket 1 517-89116-0001 -
Conn2 25 pin D connector 1 538-DBKL25PUTI -
- D-SUB Housing 1 152-9025-E -
- 16 pin Header 1 517-2316-6121TG -
PCB Printed Circuit Board 1 circuit board Order from www.expressPCB, 21 boards total for $59. Single boards may also be available from one of the wiki maintainers.

All of the parts save the circuit board can be obtained from Mouser Electronics. They are also available at many electrical parts suppliers. The circuit board can be purchased in quantities of 21 from Kits and/or single circuit boards may also be made available by one of the maintainers here.

Tools Required

15 watt (maximum) soldering iron

Diagonal cutters for trimming component leads

Thin rosin core 60/40 solder.

Wire strippers.

Three hands (a small vice will also work)

Solder the D25 Connector

Solder the D25 connector to the circuit board. pay close attention to the orientation of the circuit board and the D25 connector. Note in the photo in the following step the side of the D25 connector with 13 pins is facing up and pin 2 (on the right in the photo) is aligned with the first pad on the circuit board. Also note that the circuit board is double sided and you must make sure that you have the same side facing up as shown in the photo below. Aside from soldering the D25 plug on both sides of the board, all soldering is done on the bottom of the board.

Install the 100 OHM Resistors

Using the Component Layout, populate the board with the 100 Ohm resistors. You can determine the locations of the 100 Ohm resistors in the photo below. Start by folding one of the leads of each resistor over so it makes a U shape (the resistor should stand on its end on the circuit board). Insert one resistor at a time and solder it in place before moving on to the next resistor. If you do not insert and solder one at a time you will find that there is very little space for the soldering iron and solder to fit in between the leads of the resistors. When you have soldered all 5 resistors in place move on to the next step. Note that soldering has been completed in the below photo, you just can't see the solder as it is on the opposite side of the board.

Note the location of the 100 ohm resistors and alignment of the D25 connector

Install the 2.2K Resistors

Populate the board with the 2.2K resistors. You can determine the locations of the 2.2K resistors using the Component Layout and the photo below. Again, start by folding one of the leads of each resistor over so it makes a U shape and insert and solder them in place one at a time. When you have soldered all 4 resistors in place move on to the next step.

Note the location of the 2.2K resistors.

Install the Integrated Circuit

Solder the 74hc125 Quad Buffer in place. The square pad on the circuit board marks pin one of the integrated circuit. If you are looking at the chip from the top (pins down) with the notch on the left side, pin one is at the lower left. Some chips also have pin one marked with a small dot. Solder two opposite corner pins to hold the chip in place and then go back and solder the remaining pins in place.

Note the the notch in the end of the 74HC125 marking pin 1. Some chips may have a small dot instead of the notch.

Install the 0.1uF Capacitor

Insert the 0.1uF capacitor in the location shown in the photo below and solder it in place. The Capacitor is polarized (it has a positive and negative lead). The lead marked with a plus should be inserted into the hole that is closest to pin 14 of IC1.

In this photo you can see the 0.1 uF capacitor. note that the positive pin is marked with a +.

Assemble the IDE Connector

Next, assemble the IDE connector to 6 strands of wire. An old hard drive or floppy drive cable works well as a source for the wire. connect the wire to pins 1, 3, 6, 7, 9, and 16 on the IDE connector. Refer to the photo below. If you use a cable that doesn't have a red wire (marking pin 1) make sure to mark pin one on the connector so you don't connect it to your Kuro backwards. A red permanent marker works well for this.

Attaching the wires to the IDE connector and the IDE connector with the cap in place. If your wire doesn't have a red conductor don't forget to mark pin one with a permanent marker

Attach the IDE connector Cable

Attach the other ends of the wire from the IDE connector to the circuit board using the Component Layout and the photo below to locate the correct pads for the IDE connector wires. The pads are marked J1, J3, J6, J7, J9, and J16 on the Component Layout. It is a bit spaghetti like so take your time with this step. Making the wrong connection will definately cause problems and possibly bricking.

Inspect the Assembled Circuit

Inspect the entire circuit board for short circuits and cold solder joints. You can reheat any (or all) of the solder joints and make sure all of the connections are good and clean.

A quick once over of the solder side to check for solder bridges and cold joints can save all sorts of headaches

Button up the Cable

Place the circuit board and connector in the connector hood and close the hood making sure to screw down the strain relief over the ribbon cable. It may be necessary to trim the corners of the board off to enable it to fit inside the hood. A pair of diagonal cutters works well for this.

Here is the completed interface cable. All that is left is to close the hood.

Install the Header in the Kuro

Solder the double pin header into position on the Kuro mother board. The manufacturer of the Kuro filled the jumper holes for the Serial port with solder. Removing the solder from the jumper holes on the Kuro board is simple.

Press the tip of a 15 watt soldering iron with a good sharp tip (if the tip isn’t sharp use a file to sharpen it and tin the tip) into the hole from the back of the circuit board.


When the solder is flowing nicely, get your mouth about 1" from the front of the board and blow hard into the wet solder while at the same time removing the solder iron. You will blow the solder out of the hole leaving a hole that you can easily put a wire through.

You will also need to bridge R67 with a small piece of wire in order for the interface cable to draw operating voltage from the Kuro.