Serial console access

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Gordon
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Joined: 10 Aug 2011, 03:18

Serial console access

Post by Gordon » 11 May 2015, 07:26

I figured I best make this a new topic. I read the wiki for creating a serial connection and the connectors to use don't really seem very suitable to me to attach headers to them (and I don't really want/need the cable to be attached forever).

Now I found an old topic containing below picture and text:
Image
you can find the UART on a couple of testpoints on the board, I also found it in a couple of pinheader holes and the port on the back
Does anyone have any specifications on this? I can see those pinheader holes on the revision board (they're not on the older boards), but what is that "port on the back"? Is that the 10+4 card edge connector and if so, does anyone have a pin layout for it? I would prefer to use that one if possible, because then I would only have to create a single cable and be able to use it on every unit I wish to.

Gordon
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Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 12 May 2015, 09:05

Found some other topics that confirm the edge connector contains TTL/serial next to JTAG. No clues towards the layout though, which appears to be proprietary. However, there is a special JTAG for ARM connector that has 10 pins and if that layout is used on this proprietary connector (using pins 7-16) that would leave pins 1-4 on the left side of the polarization key slot to contain the TTL/serial connection. But which is which? I don't even spot an obvious candidate for ground anywhere on that connector?

johannes
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Re: Serial console access

Post by johannes » 19 May 2015, 01:52

Hi guys, correct, both the pin header and the card edge connector has the UART pins. There is a female card edge connector (from Samtec I think) that fits.

Easiest way to figure out the pinout of the card edge connector is to beep it with a multimeter against the test points described here: http://wiki.mybubba.org/wiki/index.php? ... cess_on_B3. If I remember correctly UART is on the "4"-side of the connector, JTAG on the other. You also need ground, which you also can beep to find.

Let me know if you need more details, I can try to dig something out (need to startup my archive-B3 though, so won't happen today).

Good luck!
/Johannes (Excito co-founder a long time ago, but now I'm just Johannes)

Gordon
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Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 19 May 2015, 03:29

Hi Johannes,

I had to dig up the old electronics box from the attic. Did not use that stuff for years, but the meter was still working (after inserting a new battery). Did use the beeper function to find Tx at 2, Rx at 4 and ground at 6 and 15. There's no ground on pins 1 or 3 (the "4" side). Did find what connector to use, but still struggling to acquire it (yes it is from Samtec). Also found a significantly cheaper version for the FTDI cable assembly mentioned in the wiki. FTDI designated this 3-wire cable as specifically for Raspberry Pi, but those are precisely the 3 wires needed to get a serial/TTL connection to the B3.

johannes
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Re: Serial console access

Post by johannes » 21 May 2015, 02:28

Ah, good to hear. As always, if you feel you have the time, update the wiki with your improvements!
/Johannes (Excito co-founder a long time ago, but now I'm just Johannes)

Gordon
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Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 03 Jun 2015, 11:22

Grmbl...

Electrical connection seemed fine but I wasn't receiving any data. I ended up soldering header pins on one of the revision boards, as in the picture above (that connector does not exist on the older boards) and plugged the FTDI cable onto it (1: GND, 4: RX, 5: TX). Again, nothing. So next I started fiddling with the wires. I verified that I got an echo with TX and RX shorted and it did. I got the same result with only RX and TX connected to the board. When connecting the ground wire everything turned black again.

While typing this I figured I could try one more thing and I reversed TX and RX: tadaaa. Either the orange and yellow wires are reversed on my cable, or the image in the wiki is wrong. Anyway, it's working now. Time to tidy up things so it won't fall apart while using it.

Gordon
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Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 05 Jun 2015, 04:28

Image:

Image

Gordon
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Re: Serial console access

Post by Gordon » 22 Jun 2015, 06:55

I should read more careful :evil:

Yellow is TX and needs to be connected to RX on the board, so there was nothing swapped except in my head. In any case, if someone wants to build this cable himself: here's what you need:
  1. A Samtec MEC1-108-02-*-D-* connector
  2. An FTDI TTL-232R-Rpi USB to serial/TTL cable
The Samtec connector is quite hard to come by. No local shop I queried could supply it and the handful of online vendors I found would not sell to a non-business. I got it from Farnell, which was not an all positive experience but they got me the part and that's what matters. As for the stars, there are multiple versions of this connector, using different contact material, surface or angle mount and some other options. It doesn't really matter which one you get, although you'll probably want to stay away from the 'NP' versions because these do not have the polarization bar (meaning you can plug it on reversed). The one I ordered was MEC1-108-02-L-D-RA1-SL and it cost me just under 4 euro.

The TTL-232R-Rpi is a stripped down version of the cable mentioned in the wiki. It only has three wires but these are exactly the three wires you need. The bonus is that it costs about 10 euro less which is a good save for something you didn't need in the first place. The wires on the cable are also not open ended but have 0.1" pitch single connectors that will fit regular pin headers on a circuit board.

Additionally I used a piece of an old scsi-1 cable I had lying around in my "maybe it will be of use some day box" and a 4-pin break away header from which I pulled the third pin (so I know which pin is ground). This way I can simply detach the cable from the card edge connector and still use it on Pi as well.

Getmarken
Posts: 9
Joined: 27 Jan 2014, 04:58

Re: Serial console access

Post by Getmarken » 13 Nov 2015, 12:00

I need to try to get my b3 work again since I failed distupgrade the debian os.
When I read your articels abot the topic I have 2 problems: 1 Too bad at english language and 2 Why is every wiki link not active?
Is it so that the edge connector can be used to get the needed connections??
When I connect the power to b3 no LED is on.

Hope uou can help me

Lasse

Gordon
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Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 13 Nov 2015, 14:25

Hi,

As a result of Excito's bankruptcy the domains have shifted several times over the past two years. The wiki is now at wiki.excito.com.

To answer your question:
Yes, the edge connector will give you access to the serial console. For me this is good, because I own multiple B3's and can use the same cable for all of them. If you don't trust your soldering capabilities you'll also like that you can build the cable without needing to solder anything to the board itself.

Other option is to solder directly to the board, as explained in the WIKI: Serial Console Access on B3. Third option, if you have a revision RF1 board, is to solder print headers as shown on the photo in this topic (right next to the battery).

Hope you manage to unbrick your B3.

OlivierC
Posts: 31
Joined: 21 Sep 2013, 08:01

Re: Serial console access

Post by OlivierC » 22 Mar 2016, 11:52

@Gordon
I've searched seller for the edge connector to avoid soldering directly to board:

Found this item on eBay.co.uk:
http://www.ebay.co.uk/itm/CONNECTOR-CAR ... 835701482?
CONNECTOR, CARD EDGE, 1MM, R/A, 14P, MEC1 108 02 L D RA1 SL 1763393

This should be the same you bought?

Gordon
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Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 23 Mar 2016, 05:16

That is exactly the one I got. Shouldn't really matter which variant you buy though, as long as the part number starts with MEC1-108-02. Beware of the versions that have "-NP" in the part number however. This one does not have the polarization key and can thus be reverse mounted to the board.

beatgr
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Joined: 01 Feb 2009, 15:25

Re: Serial console access

Post by beatgr » 23 Mar 2016, 22:19

Newark (USA) and Farnell (UK) stock this SAMTEC connector.
SAMTEC MEC1-108-02-L-D-RA1-SL Connector,
MEC1-RA Series, Card Edge, Receptacle, 14, 1 mm, Surface Mount

This is the SAMTEC data sheet
http://cloud.samtec.com/catalog_english/mec1_em.pdf

Newark
http://www.newark.com/samtec/mec1-108-0 ... dp/85T5528

Farnell (UK) / ekement14
http://uk.farnell.com/samtec/mec1-108-0 ... dp/1763393

Gordon
Posts: 1294
Joined: 10 Aug 2011, 03:18

Re: Serial console access

Post by Gordon » 28 Mar 2016, 17:27

Yeah... Got mine from Farnell. Problem with that firm is that they enforce a minimum order amount for consumers. I topped up my €4 order for the MEC with a battery offer they had running at the time: 100 AA and 100 AAA. I use those quite a lot and figured I would have emptied those boxes by now, but they turn out to be a very good buy and they'll probably last 'till 2020. Eat that, you silly pink rabbit of that other brand!

nikwest
Posts: 3
Joined: 05 Dec 2016, 18:24

Re: Serial console access

Post by nikwest » 06 Dec 2016, 13:42

I took a different route. I am using a esp8266 dev board with this firmware esp-link installed.

This way you have a wireless remote serial console, which costs you just a couple of bugs.

This could even be left inside and get power from the main board, if it wasn't for security.

PS: Cannot post links as new user

Edit: made the photo smaller
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