SparkFun Forums

[d4n1s]

Well I bought both http://www.sparkfun.com/products/275 and http://www.sparkfun.com/products/520
the processor with the JTAG Programmer/Debugger for ARM processors. I just don't know where in what order and which pins to connect to the cable... any ideas?

[itikhonov]

Here is a connector pinout: http://www.olimex.com/dev/images/arm-jtag-layout.gif
Here is a chip pinout:page 9 of http://www.nxp.com/documents/data_sheet ... _36_38.pdf

[d4n1s]

3 of the pins the trst ones and few others dont exist on the cpu

[leon_heller]

TRST is pin 20. What are the other ones you can't find?

[d4n1s]

ntrst dbgrq dbgrback vtarget. Also where do I connect the gnd pins? To the processor gnd or battery gnd? Does it matter if I connect all the gnd in a common bus on series and than on the processor or they have to be placed in different pins?

[leon_heller]

Sorry, it's nRST you need, plus TDO, TCLK, TMS and TDI.

You don't need the other JTAG signals, most targets only use the above.

1,2 are 3.3V, 4, 6, 8, 10, 12, 14, 16, 18, 20 are Gnd.

[d4n1s]

there is no pin such nTRST only TRST

there is also no TCLK

[leon_heller]

They are the same signal! The 'n' just means that it's active-low, which is also indicated by the overbar.

You don't need it, anyway.

TCK is the same as TCLK.

[d4n1s]

I have connected....

TDO TMI TMS TCK VREF NTRST RTCK all of them with the pin that has their name except NTRST that I matched it with TRST...
now there are the GND pins left Vtarget RST, OBGRQ OBGBACK left without a match.

I have 3 questions:

1) Do I just leave the Vtarget, obgrq, OBGBACK unconnected? What are they used for?

2) Can I create a single bush where all gnd pins will be connected and drooped of the battery gnd pole that supplies with power the processor or that would be a lethal mistake?

3) You said I can just use these pins u listed above, why there are more pins that their names match with the processor pins? Is there any chance that I will need to connect them on future for a specific reason?

[leon_heller]

Use nRST, not nTRST, as I keep telling you.

You only need the signals I mentioned. Don't connect anything else.

You also need pull-ups and a pull-down, details are on the ARM web site. It will probably work without them, though.

[d4n1s]

what does pull ups and pull downs mean?

also why when I design in eagle using LPC2138 libraries few pins are connected between them without me putting them?

[leon_heller]

Resistors to Vcc and Gnd.

They might be power and ground. I don't use Eagle, try the CADsoft forum. I don't trust anyone else's parts, they often have errors so I create my own.

[d4n1s]

Use nRST, not nTRST, as I keep telling you.

You only need the signals I mentioned. Don't connect anything else.

You also need pull-ups and a pull-down, details are on the ARM web site. It will probably work without them, though.

I dont understand, I connect the RST pin of the JTAG to the TRST pin of the processor?

there are also RTCK and simple TCK on the JTA, which of them I use?

[leon_heller]

I don't think that TRST is actually used; you could connect it though, to make sure.

You should also connect RESET to RST on the LPC2138.

Use TCLK, pin 9.

This should have all the information you need:

http://infocenter.arm.com/help/index.js ... 11418.html

and these are the connections:

http://www.keil.com/coresight/connectors.asp