• Home
  • Help
  • Search
  • Login
  • Register
Pages: [1]
Author Topic: Newbie question: do I need a JTAG board for the GuruPlug?  (Read 9704 times)
zzort
Newbie
*

Karma: 2
Posts: 10


View Profile
« on: April 16, 2010, 10:26:47 PM »

I'd like to get a GuruPlug Server Plus as a hobby project - mainly to see whether I can save some electricity by not running old desktop PCs as a router, DNS, web cache/proxy, NAS, firewall, etc.

I am not familiar with JTAG,  and from the website I can't tell whether I absolutely need to buy the JTAG board to get anywhere with this unit. I guess all I will need is a serial terminal and something with file storage, so I'm planning to use some combination of USB keys, Micro SD cards, USB hard drives etc. Do I need the JTAG board in order to get a terminal connection into the GuruPlug Server Plus? Or can I buy the plug without the JTAG board and still get going?
Logged

fragfutter
Sr. Member
****

Karma: 12
Posts: 280


View Profile
« Reply #1 on: April 17, 2010, 12:04:56 AM »

With the JTAG you can directly access the flash memory without a running plug. This is useful if you want to modify the u-boot (bootloader). If something goes wrong you need this to recover.

it is currently unknown if you can access the u-boot prompt without the JTAG module. This is necessary if you want to modify boot parameters (where is the kernel, which parameters, etc).

I would not buy a plug without access to the serial console.
Logged

varkey
Newbie
*

Karma: 0
Posts: 19


View Profile
« Reply #2 on: April 23, 2010, 03:54:39 AM »

I am in the same situation. I bought two Guruplugs without the JTAG module. Now after reading posts here I am confused. There is a mini usb port in Guruplug, can I use that to get serial console?

Also if its absolutely necessary to get the JTAG Module from Globalscale itself? Is it a common device which I can get from eBay or something? I searched for JTAG in eBay and found many results and are much cheaper.

I am really new to this so please forgive if the questions are stupid. Smiley
Logged

chunkyks
Newbie
*

Karma: 3
Posts: 27


View Profile
« Reply #3 on: April 23, 2010, 11:25:20 AM »

The default way to get into the plug is via ssh. The serial terminal on the JTAG is for messing with the bootloader, checking the serial console, and reflashing the device.

I have three plugs now; one of them [original globalscale] I used the JTAG serial to reflash and the SD port. I have an ionics plug that hasn't yet been booted with the jtag module attached, and I have a DockStar that doesn't offer JTAG. All three of these are in active use for all kinds of stuff.

The short answer is that "you probably don't need one". Out of the box you can ssh in and fidget with it, without needing JTAG.

Gary (-;
Logged

varkey
Newbie
*

Karma: 0
Posts: 19


View Profile
« Reply #4 on: April 23, 2010, 07:22:50 PM »

Say I want to change bootloader settings, can it be done withouth the Guruplug JTAG module?

What is the use of the miniusb port in Guruplug?
Logged

chunkyks
Newbie
*

Karma: 3
Posts: 27


View Profile
« Reply #5 on: April 23, 2010, 07:27:52 PM »

I would presume so, although I don't have a guruplug yet.

For what it's worth, the dockstar actually has a tool blparam. I don't know if it works for anything else, but it might be worth a gander.

Gary (-;
Logged

SgtPepper
Newbie
*

Karma: 2
Posts: 19


View Profile
« Reply #6 on: April 23, 2010, 07:58:41 PM »

Say I want to change bootloader settings, can it be done withouth the Guruplug JTAG module?

What is the use of the miniusb port in Guruplug?
There is no miniusb port on the GuruPlug.  There is a UART port and a JTAG port.  Both of those can be connected to the JTAG board, which has a miniusb port to connect to your PC.
Logged

varkey
Newbie
*

Karma: 0
Posts: 19


View Profile
« Reply #7 on: April 23, 2010, 08:00:51 PM »



But in the above picture, there have shown 3 connectors and out of that one is marked as MiniUSB port. I am confused. Sad
Logged

SgtPepper
Newbie
*

Karma: 2
Posts: 19


View Profile
« Reply #8 on: April 23, 2010, 08:34:59 PM »

That picture is wrong.  I too was confused at first; it says mini-USB but it isn't the right shape.  However, just in the last couple hours a bunch of documents became available on the FCC's approval site showing how it really is (including a _very_ basic manual with direction on how to connect to serial) - and it is as I described it above.
Logged

daemondust
Newbie
*

Karma: 4
Posts: 23


View Profile
« Reply #9 on: April 24, 2010, 06:10:22 AM »



But in the above picture, there have shown 3 connectors and out of that one is marked as MiniUSB port. I am confused. Sad

The port labeled "Mini USB-Port" isn't.  It's the JTAG port.  It's labeled J5 on the schematic, page 2 of the pictures, 6 of the schematic.

The one labeled "JTAG UART RS232" is J7, also page 2 of the internal pictures, 7 of the schematic.  That one is directly connected to the processor.  No protection at all, so it's 3.3v? 1.8v?  Definitely NOT RS232 voltages.
Logged

zzort
Newbie
*

Karma: 2
Posts: 10


View Profile
« Reply #10 on: May 02, 2010, 04:14:36 PM »

Seems like GlobalScale's website has created quite a bit of confusion. Perhaps they should update it with more accurate information now the design of the GuruPlugs is finalized.
Logged

Romani
Newbie
*

Karma: 0
Posts: 2



View Profile
« Reply #11 on: May 09, 2010, 09:03:27 AM »

Hello, i planning to purchase GuruPlug Plus, for using it torrent downloader, ftp, maybe jabber bot, so my question - is it worth for me to buy JTAG board ? Do factory installed OS (Debian, probably) offer all things i need without need to reflashing NAND on other?
Logged

escarroll
Newbie
*

Karma: 0
Posts: 2


View Profile
« Reply #12 on: May 10, 2010, 12:24:08 PM »

In order to connect with a serial cable or JTAG, ( 2 different Serial type interfaces ) you will need the JTAG board.  You may not need JTAG but you most definitely will need the possibility of serial console access, if you are going to be reconfiguring interfaces for IP access.  IF your not careful you could end up disabling and interface you need to talk to the server remotely and the only way to recover it is to use the serial console access.
Logged

hausschuh
Newbie
*

Karma: 0
Posts: 33


View Profile
« Reply #13 on: May 11, 2010, 04:23:50 AM »

Unfortunately I still don't get it.
I'm on a NSLU2 right now and I will upgrade to a Sheevaplug or Guruplug.

To install Debian on the NSLU2 I had to go into the upgrade mode by pressing and holding down a little hardware button. Then I was able to flash a custom debian firmware (installer) over the network and install it to an external disk. So whenever my hard disk would blow up and so does the operating system I could redo all the steps from upgrade mode to flashing over the network and the NSLU2 would be up and running again.

So I'm thinking about the debian installation to a Sheevaplug which is only possible to a SD card (according to www.cyrius.com). After you did some pre stuff you come to this step:
Quote
Now connect the USB stick to your SheevaPlug or enter the SD card and connect a mini-USB connector in order to access the serial console
and quoted from this thread:
Quote
With the JTAG you can directly access the flash memory without a running plug. This is useful if you want to modify the u-boot (bootloader). If something goes wrong you need this to recover.
and:
Quote
There is no miniusb port on the GuruPlug

So what I understand is that you need the additional JTAG for the Guruplug to go into this "serial console" (because there is no miniusb port) mode for installing debian (I know it is already preinstalled but in case you want to reinstall it for some reason) AND if you somehow blow up your operating system (maybe your SD card just dies because of too many read/write cycles) you need the JTAG again for redo all the necessary steps.
« Last Edit: May 11, 2010, 04:25:42 AM by hausschuh » Logged

tbm
Full Member
***

Karma: 7
Posts: 121



View Profile WWW
« Reply #14 on: May 11, 2010, 06:02:11 AM »

Yeah, you can put the NSLU2 into upgrade mode and flash a good image to it.

On the SheevaPlug, what you'd do instead is to connect a serial console (via mini-USB) and then you could talk to the boot loader.  And you could load a good image via the network or a USB stick.

On the GuruPlug, the serial console and JTAG are not integrated into the device (as with the SheevaPlug) but is a separate device that you can connect to the GuruPlug.  You'll need that JTAG board if you ever want to access the serial console of your GuruPlug (i.e. to see the boot process and issue commands in the boot loader) or to use JTAG (this is sort of like an upgrade mode but it also works when the boot loader has been damaged).
Logged

Pages: [1]
Print
Jump to: