B2 rev RD serial access

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lenger
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B2 rev RD serial access

Post by lenger » 05 Nov 2010, 09:26

I was trying to access the serial interface of my B2 following this excellent post:
http://forum.excito.net/viewtopic.php?f=8&t=206

Unfortunately, I can't find J2 on my board, which is revision RD1 (or RD2 if i should trust the white sticker).

Anyway, near the blue LED, there seem to be a soldering space for a DSUB-9 connector. Is this connected? And which voltages does it use. There seem to be few non mounted components nearby, so it doesn't look very promising at first glance.

So the actual question is; how do I access the serial port on the B2 rev RD?

There seem to be a lot of test pads and unused connectors around. Can these be used for anything cool? Are there any schematics available?

BR,
Henrik

Magnus
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Re: B2 rev RD serial access

Post by Magnus » 16 Nov 2010, 03:11

Hi Henrik,
Here is the RT/TX connections for the B2 (all revisions). Use the guide from the thread you refer to.
The DSUB pads can't be used as the necessary components aren't mounted. Hope this will get you started!
/Magnus
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MouettE
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Re: B2 rev RD serial access

Post by MouettE » 12 Oct 2011, 12:14

I'm tryning to get my console to work, but I have difficulties. I bought a FTDI USB-TTL converter as advised on the wiki (TTL-232RG-VREG3V3-WE) and had it soldered on my motherboard as described in the previous post. Then plugged in my computer and started minicom. The COM parameters are 115200 8bits None 1. I can see the console output, which is already awesome (added to the fact that the b2 still works after the surgery) ; however I cannot send anything. The keys typed don't get printed, and even blindly I can't log in. I have the following connections on my board :

on RX board <-> orange TXD cable
on TX board <-> yellow RXD cable
on GND board <-> black GNS cable

I suppose that the 3.3V pad should not be connected to the 3.3V cable, because they're seem to be both VCC outputs.

I suppose the pad are connected somewhere on the board, I could check that the link is still OK if I knew pad destination.

Anyway I was just wondering if anyone got this to work, and if there were anything I did wrong or forgot.

Thanks everyone !

johannes
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Re: B2 rev RD serial access

Post by johannes » 13 Oct 2011, 11:35

Hmm, strange, this usually works without problems. If you can, try measuring the TX signal with an oscilloscope (or if not at hand, use a multimeter set to AC, it can usually detect traffic if you just do much enough traffic. For isntance press and hold 'U', this gives a square wave if I remember correctly, which should maximize the AC voltage.)

So, do this and see if your FTDI cable really is sending. If it is, do the same measurement on the B2 board to see that cabling is OK.

(You are probably right that the 3.3V should not be connected - if it is an output you don't shouldn't, it's an output on the B3 board).
/Johannes (Excito co-founder a long time ago, but now I'm just Johannes)

MouettE
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Re: B2 rev RD serial access

Post by MouettE » 24 Oct 2011, 02:52

After a contact with FTDI, they suggested a very simple test I didn't think about : contact the TX and the RX wires together on the cable, open a console and see if sent characters echo back. Which didn't work so I sent back the cable for an exchange. I shall keep you posted when I'll receive the new one.

MouettE
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Re: B2 rev RD serial access

Post by MouettE » 07 Nov 2011, 10:05

I just received my new FTDI cable. After a quick test, I soldered it to the board, and it works fine. Awesome !

paulchany
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Re: B2 rev RD serial access

Post by paulchany » 08 Jul 2014, 15:52

MouettE wrote:I just received my new FTDI cable. After a quick test, I soldered it to the board, and it works fine. Awesome !
Does it mean that that if one messed up once the uboot image on the flash memory on Bubba2 with this cable, she/he can to flash the uboot image again and again until she/he get the proper uboot image on the flash memory?
Best, Pali

johannes
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Re: B2 rev RD serial access

Post by johannes » 08 Jul 2014, 17:06

paulchany wrote: Does it mean that that if one messed up once the uboot image on the flash memory on Bubba2 with this cable, she/he can to flash the uboot image again and again until she/he get the proper uboot image on the flash memory?
Yes. That serial port is what we use for production programming. You can read about the procedure in the datasheet of the CPU, but it is a bit complex, it's a two-step operation. The hardware loader (which is what communicates on the CPU end when there is nothing else to boot from) can only store in internal RAM, which is too small for uboot. So you need to make an intermediary loader, that is first loaded to RAM and then executes from there, that loads the full uboot from serial port to flash.
/Johannes (Excito co-founder a long time ago, but now I'm just Johannes)

MouettE
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Re: B2 rev RD serial access

Post by MouettE » 09 Jul 2014, 20:32

I have written and tested a few days ago a script which executes this procedure on the Bubba 3. I have been able to run a u-boot image from the serial port and it works quite well. I will soon post the details on the dedicated u-boot thread.

However I don't have any clue about doing that on a B2. I would try if I could (and if it is technically possible), but I miss the adapted u-boot sources and the technical details of the board to implement it.

Maybe you have something to begin with in Excito archives ??

paulchany
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Re: B2 rev RD serial access

Post by paulchany » 19 Jul 2014, 09:56

MouettE wrote:I just received my new FTDI cable. After a quick test, I soldered it to the board, and it works fine. Awesome !
Can I use a regular A-B USB cable as is described at this link bellow?
http://forum.excito.net/viewtopic.php?t=1000
Best, Pali

MouettE
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Re: B2 rev RD serial access

Post by MouettE » 19 Jul 2014, 10:43

paulchany wrote: Can I use a regular A-B USB cable as is described at this link bellow?
http://forum.excito.net/viewtopic.php?t=1000
Short answer : No
You need some logic to convert TTL signal to RS-232 (and then to USB if you don't have a serial connector on your PC).

paulchany
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Re: B2 rev RD serial access

Post by paulchany » 07 Jan 2015, 16:13

MouettE wrote:
paulchany wrote: Can I use a regular A-B USB cable as is described at this link bellow?
http://forum.excito.net/viewtopic.php?t=1000
Short answer : No
You need some logic to convert TTL signal to RS-232 (and then to USB if you don't have a serial connector on your PC).
All right!
A have finally the FTDI cable.
1. I shall test it as MouettE did ( contact the TX and the RX wires together on the cable, open a console and see if sent characters echo back ). Don't know only how to open a console on my Arch linux desktop system and how to send characters?
2. The hyperlink: http://viewtopic.php?f=8&t=206 doesn't work anymore. Has one this guide to share with me?
3. From where can I download the uboot image?
Best, Pali

MouettE
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Re: B2 rev RD serial access

Post by MouettE » 07 Jan 2015, 21:40

paulchany wrote:1. I shall test it as MouettE did ( contact the TX and the RX wires together on the cable, open a console and see if sent characters echo back ). Don't know only how to open a console on my Arch linux desktop system and how to send characters?
2. The hyperlink: http://viewtopic.php?f=8&t=206 doesn't work anymore. Has one this guide to share with me?
3. From where can I download the uboot image?
1. You can use screen or minicom to open a terminal on your serial console. screen is probably simpler to setup but I think that minicom offers better compatibility. Install minicom with pacman and create the /etc/minirc.dfl file with the following content (check the port name on your kernel messages after plugging your ftdi cable) :

Code: Select all

pu port             /dev/ttyUSB0
pu mdialpre         
pu mdialsuf         
pu mdialpre2        
pu mdialsuf2        
pu mdialpre3        
pu mdialsuf3        
pu mconnect         
pu mnocon1          
pu mnocon2          
pu mnocon3          
pu mnocon4          
pu mhangup          
pu mdialcan         
pu rtscts           No
From there you can run minicom (your user must be in the uucp group to access the serial device) and try to type characters. They should be echoed back on the terminal. To exit minicom press Ctrl-A then q.
2. The correct link is : forum.mybubba.org/viewtopic.php?f=8&t=206
3. Maybe you should explain what you're trying to do now. If you're still on a b2 you should know that there is no uboot image available for download AFAIK.

paulchany
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Re: B2 rev RD serial access

Post by paulchany » 08 Jan 2015, 02:06

MouettE wrote:
paulchany wrote:3. From where can I download the uboot image?
3. Maybe you should explain what you're trying to do now. If you're still on a b2 you should know that there is no uboot image available for download AFAIK.
Yes, I'm still on my Bubba 2. I'm trying to install on Bubba 2 the newest kernel available.
Now my Bubba2 has the Linux b2 2.6.39.4-13 #1 Sat Apr 21 00:42:46 CEST 2012 ppc GNU/Linux kernel and the Wheezy operating system, without Bubba's packages.
This kernel that I have now is not compatible with hostapd package.
I think that that there is a newer kernel for Debian Wheezy operating system, right?
And because of uboot that I have now on my Bubba 2, the newest kernels can't be installed on my Bubba2, right?
I think that that if I could have the newest uboot image on my Bubba2, then I can to install newest kernels for Wheezy operating system, so I could have the setup of hostapd so I can setup my Bubba2 as a Home WiFi AP. That is my goal.
Best, Pali

MouettE
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Re: B2 rev RD serial access

Post by MouettE » 08 Jan 2015, 13:42

paulchany wrote:And because of uboot that I have now on my Bubba 2, the newest kernels can't be installed on my Bubba2, right?
The u-boot bug that prevent newer kernel from booting does not affect the Bubba 2. You can boot it with newest kernel without upgrading u-boot (in any case we don't have the original modified u-boot source for the b2 so it would be a very hard work to compile a newer and working u-boot for the b2).

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