Stumped on getting the XTAG2 to talk to a L1-128 processor

Technical discussions around xCORE processors (e.g. xcore-200 & xcore.ai).
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rp181
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Post by rp181 »

That would be great! This is killing me...

Also see this that I posted now:
http://4hv.org/e107_plugins/forum/forum ... php?121490
might be relevant.


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segher
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Post by segher »

rp181 wrote:Now I get a error, rather than no device found. When trying to execute, this comes up:
set_configuration_error -6
set_configuration_error -6
xrun: Problem in connection to device
That's -ENODEV ("no such device"), and it looks like this comes from libusb.
Sounds to me like you managed to crash the xtag2 (or got it into a state where
it won't talk USB, anyway). Fun!
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rp181
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Post by rp181 »

Yep, that looks like the problem. I unplugged and re plugged it in, and it is back to the xrun error.

Too bad, I thought I had made progress :(
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Post by snoopy »

I had a look when I got home but still can't figure out where its going wrong.

Maybe try break down the analysis a bit more? I think you already have judging by the pics you posted on 4hv.org. What have you done so far in terms of analysing the JTAG signals? Have you done any comparisons from whats leaving the XTAG to whats arriving at the board?

S
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Bianco
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Post by Bianco »

There's also an option for xrun/xgdb to lower the JTAG speed.
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Post by snoopy »

Bianco wrote:There's also an option for xrun/xgdb to lower the JTAG speed.
But hes only using one core with no buffers :s The XTAG should be able to run at full speed with that config :/
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rp181
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Post by rp181 »

There's also an option for xrun/xgdb to lower the JTAG speed.
Are you talking about the JTAG divider in run configurations? I have tried changing that, but it seems to remain at 12.5mhz. I will give it another shot, if anything, I will reduce noise I am seeing on the probes.
Maybe try break down the analysis a bit more? I think you already have judging by the pics you posted on 4hv.org. What have you done so far in terms of analysing the JTAG signals? Have you done any comparisons from whats leaving the XTAG to whats arriving at the board?
I am going to give it another step by step after putting the buffers back on when I get home, but here is what I have been doing
1. With power off, the board is connected to the XTAG.
2. I turn on the 3v3 supply, which reaches 3v3 after roughly 30ms. The board brings up the 1v supply after ~30ms from when the 3v3 supply is stable. It draws 20-30ma at this point.
3. I hold TRST to gnd (which is also tied to the MODE pins), and touch the RST pin to the gnd, as to boot into JTAG mode. I disconnect both RST and TRST from GND, and let the on board pullups take them high (47k ohm to 3v3)
4.I plug in the XTAG, and open up Run configurations. To test, I am pressing "refresh" (which promptly comes up with no devices)
5. When I press refresh, the XTAG pulls TRST low, then pulls TDSRC high. It does it again, then two more times after a considerable delay.
Zoomed in on 1 set of 2:

6.On my board, TDSNK remains silent (it looks like that noise is an artifact). On the XTAG, TDSNK responds with a pulse.
7. TCK is as shown (ignore the artifacts in the other signals)

It is at 12.5mhz

What is TMS supposed to do? Does Debug do anything? I had disconnected it when taking the buffers off. I will have to see if that does anything on the XK-1. I also do not have the serial line or XLinks connected.
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Post by snoopy »

rp181 wrote:What is TMS supposed to do? Does Debug do anything? I had disconnected it when taking the buffers off. I will have to see if that does anything on the XK-1. I also do not have the serial line or XLinks connected.
TMS is a state test for the JTAG state machine and is definitely needed.

DEBUG is used for multiple core systems to prevent core skidding where multiple cores would stop out of sync. So the DEBUG can be used so that all cores stop at the same point. If the system has many cores then DEBUG can be used but single core applications don't need it wired. Otherwise wire it with a pull up so that if the JTAG asks for cores to stop, it pulls it down hard and all cores should stop. Its supposed to be bi-directional but I don't see it working without buffers in each direction....never seen any applications with it :/
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rp181
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Post by rp181 »

Sorry I didn't get that done, I got home late.

Yes, I have TMS. I just don't see any activity on it, so what is supposed to happen on the line?
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Post by snoopy »

TMS won't show anything until the JTAG chain is set up. It should remain low until the boundary scan is complete and the JTAG is ready to go.

As far as I know (its been a while since I had a look at JTAG traffic), the TMS will remain low until the JTAG state is ready to change. Once it is ready, TMS will be high and on the next TCK it will change state, TMS will then go low again and remain low until JTAG state machine is ready to move to the next state again.

Do you get any data on TDI and TDO? If these don't work, the JTAG boundary scan will fail.

EDIT: Also check TCK. Without a good clock nothing will happen on any of the JTAG lines

S
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