Olimex Support Forum

OLinuXino Android / Linux boards and System On Modules => iMX233 => Topic started by: baltazar on November 08, 2012, 03:29:11 pm

Title: First Olinuxino connection
Post by: baltazar on November 08, 2012, 03:29:11 pm

it is my first attempt to connect to Olinuxino micro. I have the SD card from Olimex with prebuilt linux inserted. I don't have the USB-ttl cable yet. can I access from my linux host to the board using USB-USB or I need to use USB-ttl?

Title: Re: First Olinuxino connection
Post by: flavigny on November 08, 2012, 06:03:45 pm
of course, it is easyer to buy Usb-ttl cable (8 $ from olimex, or 3 $ from china)

However, I continue for fun. Yes, you can! it is possible to login by usb plug.

My sandbox is 'yocto', created by Otavio and downloaded from here: http://tech.groups.yahoo.com/group/olinuxino/message/1530 which contains module for Prolific Pl2303

Some precisions about using usb-usb cable.

when you will plug the cable in the OlinuxMicro board, it will be usable ONLY if module exists for your model (identified by Pnp Vendor Id & Model Id).
I tried two cables usb-usb sold as "data transfer" (Direct-LinQ). "Out of the box" they are not usable a tty link. (Vendor:prodcut Id is 067B:0000 wich is not asscoated to any module on Unbuntu 12.04 nor my OlinuxIno.

So here is "my" solution:
First (1) I build a cable with TWO usb-ttl as:  http://cgi.ebay.fr/ws/eBayISAPI.dll?ViewItem&item=180953299346&ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Connect the two ground
Cross Txd and Rxd
Drop + 5V.
We will call it "null-usb" (legacy of vintage null-modem).

When plugged, if no more usb-serial is connected, it will be /dev/ttyUSB0 .

Last (2): On the sdcard, I modify (last for me) line 'getty' in /etc/inittab to allow login on /dev/ttyUSB0, specifying speed:
1:2345:respawn:/sbin/getty 9600 /dev/ttyUSB0

Note that, ALAIK, (developed in another post) this driver is not operational in ArchLinux distro indicated by Olimex.

Title: Re: First Olinuxino connection
Post by: baltazar on November 08, 2012, 07:03:20 pm

thanks for your reply! My main idea was to login using the USB-ttl and send raw data using the USB through a webcam.
I know that olinuxino-micro maybe is not powerful enough for doing this but I would like to try.
I will certainly buy the USB-ttl cable since I need both connections in order to use the camera.
I didn't get why a normal USB-USB cable should not work...
can you maybe give some more detail about this?

Thanks a lot!
Title: Re: First Olinuxino connection
Post by: flavigny on November 08, 2012, 07:16:59 pm
"normal usb-usb" does'nt exist. It is not like a null modem!

In true life there is TWO kinds of Usb-A to Usb-A cables:
- passive one, as described in the next answer
- active "data-transfert" cable such as: http://www.usb-port.com/bf100c.html

Remember: there is no-issue "crossing" wires (as Rx and Tx): data flows uss two wires (D+ & D-) shared by the two directions.
Usb-Usb data transfert contains a controler with two sides showing usb peripheral.

When plugged, my above Usb-Usb LinQ appears in lsusb as 067B:0000 and doesn't relies to /dv/ttyUSBx .

In other words: usb-usb will be usable as tty access ONLY if you have drivers installing it as serial port (for your distro OlinuxIno, AND for your workstation). (modinfo pl2303 lists a lot of matos for 067B, but not 067B:0000 )

Of course, such a driver is possible, but I have never seen it.

Note also that an usb hub allows multiple connexions to ONE HOST, but not to peripherals (reserve debug cable for debug!)

Title: Re: First Olinuxino connection
Post by: nidalpres on November 11, 2012, 12:36:11 am
To connect olimex-MICRO board to PC as USB device you need A-A type USB cable, or male-male type A UAB cable (i.e. like this http://www.amazon.ca/gp/product/B002ZKNRMQ/ref=s9_simh_gw_p23_d0_i2?pf_rd_m=A3DWYIK6Y9EEQB&pf_rd_s=center-2&pf_rd_r=1455PYV0XA4J78J2SW98&pf_rd_t=101&pf_rd_p=1375923922&pf_rd_i=915398)

You will also need to set your board to behave like USB device and you do that by recompiling kernel and setting up boot scripts and what not, but that is different story I guess.