Connecting the Serial Adapter

[grrrrrlj]

Hi All,
I've read all the forum topics about fixing a bricked XO, but unfortunately they were all geared to people who know what they're doing. Can anyone point me to a tutorial on how to connect the recommended serial adapter to the xo's motherboard that's written for dummies?

[ncarrol]

Do you want to use a second XO, linux machine with Python, PC hyperterminal, or Mac (?) to communicate with the bricked XO ?

[ncarrol]

Here is an example of using a second XO. Does this help ?

I fixed several "bricked" XO's caused by the loose RTC battery using a Sparkfun (sparkfun.com) USB to serial breakout board BOB-00718 ($15) and a three wire null modem cable to the XO (TX to RX; RX to TX; ground to ground; do not connect 3.3 volt -- supplied by USB port). The cable connector was a copper foil (tape) pattern on a piece of plastic and was wedged under the pins of the connector of the XO. An alternative is copper wires imbedded in epoxy glue and filed flat with a hobby file. Also needed is a USB A to USB mini 5 pin cable ($4).

A second, working XO was used as the terminal via the USB port (any). The terminal software was minicom obtained by "YUM install minicom" (as su ) and configured using minicom -s per:

http://wiki.laptop.org/go/Fix_Clock

An additional configuration step was to change the flow control to software YES and hardware NO.

The pinouts of the XO serial port are given in:

http://wiki.laptop.org/go/Serial_adapters.

The lower pin (white dot at back of connector) is pin 1 (3.3 volts -- unused). Pin 4 at the top is ground. Pin 2 is TX and pin 3 is RX. As a safety factor, remove the main battery of the "bricked" XO before connecting or disconnecting its cable.

Start the XO used as the terminal and run the Terminal Activity and then: su and then with: minicom USB0 . Start the "bricked" XO and a list of options will appear on the terminal with the last two lines of "Page fault" and "ok" .

Enter the commands and date / time values given in the Fix Clock article. Example line (ss mm hh dd hh mm yyyy set-time):

ok select /rtc
ok decimal
ok 01 30 13 31 01 2010 set-time
ok

A 01 in the month field (all others 00 or 0000) is sufficent to allow booting. The actual values can be used or the date command used later on the fixed XO. Ignore the date / time error fault message if you use only the month.

Power down the fixed XO with the power switch, shutdown the XO terminal, and remove the cable from the fixed XO. Power the fixed XO on and it will try to find a boot device and then boot.

As a side bar, the driver ttyUSB0 in /dev is recreated each time the XO terminal is started. IF the device is not present and working (in my case, connected 3.3 volt pin on serial port, in error) the driver will not appear. Also, the device should appear as fdti_sio in the list of devices displayed by the command: lsmod .

Finally, The RTC battery is a rechargeable battery and is recharged ONLY when the XO is powered on. So, if the battery may be discharged, leave the XO powered on for several hours, even though it does not boot. Its voltage is 2.5 to 2.7 volts during most of its discharge cycle. CAUTION: the battery holder is glued with a weak glue. If you must remove the battery (not recommended), firmly hold down the holder and use a twisting motion (not prying) of a screwdriver between the holder and the battery to remove the battery.

[ncarrol]

And here is something using hyperterminal on a PC:

http://en.forum.laptop.org/viewtopic.php?f=2&t=430&start=60#p559804

[ncarrol]

OOPS !!

The correct format is ss mm hh dd mthmth yyyy. The example line is correct.

[kscott22]

I really appreciate this thread -- I needed it. Unfortunately, I'm super inexperienced and so I'm still a bit confused.

I'm trying to connect an XO to a Windows laptop. I got the Sparkfun serial adapter and have HyperTerminal installed on my PC. I've got the XO's motherboard exposed.

I'm just wondering exactly what I need to connect the serial port to the XO and to my laptop -- and where I can get this equipment. Is there any way someone could post a photo or link to a photo of everything once it's connected (specificially the XO connection to the serial adapter).

I'm trying to help a student fix her XO and am clearly out of my comfort zone -- I really appreciate all your help!

[ncarrol]

Please post which Sparkfun adapter that you have. Then, a better answer can be supplied.

The serial adapter must be a version that provides signals at 3 volts (not 5 volt or 12 volt) to and from the XO. The adapter is needed to reduce the voltage of the signals from the serial port on the PC (which may be 5 volt or 12 volt).

Only three wires are needed from the adapter to the XO: the transmit signal (TX), the receive signal (RX) and ground. The RX from the adapter is connected to the TX of the XO, the TX of the adapter is connected to the RX of the XO, and ground to ground (this is actually a simple "null modem cable"). Connect the 3.3 volts from the XO to the adapter ONLY if that is required to power the adapter. A standard (straight through) or null modem serial cable (as per adapter documentation) connects the adapter to the PC. A serial cable is an "electronics store" item. Hyperterminal should be set up with the correct parameters. These (such as speed, parity, etc) should be the same as given in the above wiki link about serial adapters for the linux minicom terminal software (the USB port emulates a serial port) plus setting the data flow control to software control.

The link (serial adapters) above does provide the pictures for the XO serial port and the signal designation of the pins. The connection of the cable to the XO connector can be done in a number of crude ways. I simply imbedded the ends of the cable in epoxy glue (wires separated at the distance to align with pins of the XO connector) and then filed the dried end to a flat shape of a thickness of about 1/32 inch and the width of the connector. This thickness was was adjusted so that it just fit under the pins of the XO connector to provide a slight pressure contact between the wires and pins. Take care that the wires do not touch each other and align with pins in the XO connector. Also, the connector must be insulated from the circuit board components near the connector (remaining dried glue or a piece of tape).

Note that a USB to serial adapter could be used on a PC. The driver can be downloaded from Sparkfun and a Windows Wizard (starts when you plug USB cable / adapter into the PC) will step you through setting up the USB port /adapter to emulate a serial port). I have not actually tried this yet -- the second XO was simpler for me. A post above gives a link to an example of using a PC / Hyperterminal.

[kscott22]

Thank you so much for your help! I think I understand, but just to clarify....

Here's the adapter I have:

I couldn't get the focus clear enough, but it is a "3.3V FTDI Basic." I believe this is is the correct adapter, right?

Here's a view of the other side:


Based on your post, I think I should connect a USB cord to the yellow end and connect it to my PC, like so:


Then I believe I need to find the RX, TX and ground wires you mentioned and plug them into the black end:


If I'm understanding your post correctly, I can get all three of these wires if I buy a serial cable from an electronics store, like RadioShack, right? Once I plug them into separate holes in the black end (does it matter which holes?), I connect them to the XO, correct?

Again, thank you for all your help! You have no idea how much I appreciate it!!! (I definitely have some forum paying it forward to do.)

[ncarrol]

What you have appears to be a Sparkfun USB to serial board. The device is Basic Breakout Board -3.3 V with part number DEV08772 (NOT to be confused with Basic Breakout Board -5 V DEV09115). This link is:

http://www.sparkfun.com/commerce/product_info.php?products_id=8772

Schematics and driver downloads are there.

Your picture shows that you have the cable to connect the board to a USB port on a computer.

The black connector is a six pin connector. You need three of the six lines. Pin 6 is ground. Pin 3 TXO. Pin 2 is RXI. I believe the other signal pins can be ignored if you use software data flow control. Do not use 3.3 volt pin --- power is supplied by USB .

Three simple single wires are need to connect from the black connector to the XO connector.
Ground to Ground. RXI (sparkfun board) to TX (XO connector). TXO (sparkfun board) to RX (XO connector). I used a three wire ribbon cable (with my BOB-00718), which makes the fabrication of the connector at the XO easier (as described in earlier post) . ( I tried to find ready made "ftdi cable" mentioned for your black connector, but could not find it on the site.) Using wires as pins into the connector may be sufficient.

The Windows Wizard must be run (see above post) to use this on a PC. The driver may have to be downloaded and unzipped (if Wizard can not find it). I have not actually done this yet (currently using XO with minicom application). Will try to do this with my breakout board BOB-00718 (has solder holes rather than connector) within the week.

[ncarrol]

Works ok on PC using Hyperterminal.
Driver download on Sparkfun site links to FTDI site (chip manufacturer).
Download VCP driver for FT232R for my machine (Windows 2000).
Unzip file.
Plug breakout board (via USB cable) into PC.
New Hardware Wizard starts.
Asks where to find driver. Browse to directory where unzipped files are located.
Step through Wizard. (My install had "TAPI" error, which I cancelled out of -- related to missing choices in "Region" box)

Power off PC and make connections from breakout board to "bricked XO" (the internal RTC battery must be charged).

Power on PC.

Enter Hyperterminal and open new connection (under FILE).
Shows properties with USB as COM3. Click on Configure and select 115000 (speed), 8 (bits), N (parity), 1 (stop bit), XON / XOFF (Control).
Initiate Call.

Power on XO. A page of XO firmware options will appear on the Hyperterminal with the last being "Page Fault". Enter the date / time per previous posts and power down XO and disconnect cable per previous posts.

Power on XO and it will try to find a boot device and boot.

[ncarrol]

Found some in expensive connectors with spacing of 0.1 inch on Sparkfun.com site. They might be helpful in making the cable between the adapter board and the XO.

6 pin Male Header PRT-09015
6 pin Female Header PRT-09429

The male header should fit the black connector on the sparkfun breakout board.
The female header might possibly be used for the XO by cutting it down to 4 pins. I think the pin spacing on the XO connector is also 0.1 inch.

Simply solder the three wires to the headers. You can always order the correct Molex connectors for the XO from Digilab.com , which are given in the links in the first post.

[kscott22]

ncarrol,

Thank you SO much. You've been a great help. Work has kept me super busy this week, but I'll try the XO-PC connection in the coming days. I'll let you know how it works out. Thanks again for all your time and advice -- you're a life saver!

[kscott22]

Okay, I'm trying it out now. Sorry to ask for even more help, but I've got one last (I hope) question:

Do I need the 6-pin headers or can I just attach the wires?

I used three simple wires and inserted them into the appropriate holes on the sparkfun adapter. Now, I'm trying to connect them to the J1 of the XO. It has four metal prongs with space between each. Without a header, how should I insert the wires?

From left to right, should I have the RXI wire connect to the first metal prong, the TXO wire connect to the second and the ground wire connect to the last prong? Or am I completely off?

Thanks again.

[ncarrol]

Having the correct connectors always makes things easier and more reliable and safe, but makeshift connectors can serve the temporary purpose -- if you are very careful about making the correct connections.

Wires of the correct size (about the size of prongs on XO connector) can be inserted into the black connector on your Sparkfun DEV08772 USB to serial adapter. I can only refer you to the schematic for pin assignment (which is given above), but I cannot tell you which end is pin 1 (I do not have one). There should be some markings on the board to identify some of the signals. Frequently, connector pins go from left to right while looking into the end of the connector.

At the the XO end, some type of connector must be supplied, or fabricated, to reliable align and hold the three wires against the three (of four) pins (prongs). The above posts gives two ways that I have used. One is to imbed the three wires in epoxy glue and then shape (file) the dried epoxy to fit under the pins in the XO connector and align the wires (which now have a flat ,exposed surface from filing) with the pins. The other is to use a copper foil (tape) pattern on thin plastic and solder the wires to the copper foil. In either case, this makeshift flat connector is sized to just fit under the pins in the connector on the XO with a slight pressure. This pressure maintains the electrical connection between the wires (foil) and the pins (prongs).

On the XO, the bottom (or left) pin (1 of 4) is pin 1 (3.3 volt) and is NOT used. Pin 2 is TX. Pin3 is RX. Pin 4 (top or right) is ground. Sparkfun TXO goes to XO RX; Sparkfun RXI goes to XO TX; Sparkfun ground to XO ground (top or right).

[asifali418]

Edit postReport this postReply with quoteRe: Power light on, but XO won't power up
by asifali418 » Tue Mar 23, 2010 11:55 pm

hello sir i buy brand new aapter for my xo.but its not working
here is the link wich adopter i used.
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... K:MEWNX:IT
and i use desktop with window xp pro i download the driver.i used the hyperterminal.but no luck i but 115200 none 8 1 and ox on off.but no luck can u guys tell me what i doing wrong.pls help me