Installing a serial interface to Bubba
Posted: 21 Mar 2007, 19:22
A few users wondered how to install an RS232 port to Bubba, enabling a direct shell access. This could come in handy if you messed up your network settings and need to restore, or probably for a lot of other good reasons I can't think of right now.
This is just a brief guide requireing some basic hardware knowledge. Let me know if anything is missing or need to be clarified.
*** NOTE ***
This requires you opening your Bubba and soldering wires to surface mount pads. You do risk destroying the hardware if not done carefully! This may void your warranty!
*** NOTE 2 ***
If you read note one and still want to proceed, be sure that you work in an ESD safe environment. This is something home users often neglect, something that very well may cause strange and inexplainable errors. A good place to do the dissasembly and soldering is actually on your kitchen sink. Make sure to touch the metal surface before opening Bubba.
Ok, action:
The Bubba internal serial port is a "TTL level" port (3.3V level), and will not work directly towards your PC without a 3V TTL - RS232 converter. You can either build something yourself (i.e. using something like the Maxim MAX3232 IC). Make sure to select one working with 3.3V, since some of them only work with 5V power supply.
The other (easier) option is to buy a ready-made converter board. A quick google search:
http://www.futurlec.com/Mini_RS232_TTL_3V.shtml
I also found one that looks nice at ebay:
http://cgi.ebay.co.uk/RS232-to-3-3-Volt ... dZViewItem
EDIT: A bit expensive though.
(This one needs 5-20V power supply, this is available on the board at the disk connector).
Note that I haven't ordered from any of those, and can't make any promises on their behalf.
Anyone know of other vendors?
So, do like this:
1) Remove the four hex screws on the rear panel.
2) Remove the rear panel, and gently slide the board (and disk) out of the case. If it's tight, loosen the four screws at the front as well. It is safe to pull at the USB connectors.
3) Now the board is exposed. The connector pads are located near the side of the board:
EDIT: (The image is for Bubba rev B board. The same things will work at the rev A board, but some details in the image may differ. For example, the resistor R79 next to the connector (J2) is only present in the rev B board. )
4) The signals:
Solder wires directly to the pads on the board, or, use a connector in between (the Harwin M50-3150522/M50-3500542 will fit, available from Farnell, art. no: 3078190 and 1022305). Be careful when soldering, if you heat up the pads too much, they may release from the board. Connect RX to the adapters TX (Tx from the PC to Rx on Bubba), and vice versa.
5) Connect the serial cable to your PC, and start a terminal program (such as windows HyperTerminal). Set your COM port to 115200 bps, 8,0,1. No hardware handshake.
6) Start your Bubba. The Linux boot log should appear in Hyperterminal. When booted, you'll get a login prompt. Just login as root (password is excito if you haven't changed it), and you're done!
Other useful links:
http://www.interfacebus.com/RS232_Pinout.html
http://www.farnell.com/
Please let me know if any information is missing, or if you have ideas on how to make this easier.
Good luck!
This is just a brief guide requireing some basic hardware knowledge. Let me know if anything is missing or need to be clarified.
*** NOTE ***
This requires you opening your Bubba and soldering wires to surface mount pads. You do risk destroying the hardware if not done carefully! This may void your warranty!
*** NOTE 2 ***
If you read note one and still want to proceed, be sure that you work in an ESD safe environment. This is something home users often neglect, something that very well may cause strange and inexplainable errors. A good place to do the dissasembly and soldering is actually on your kitchen sink. Make sure to touch the metal surface before opening Bubba.
Ok, action:
The Bubba internal serial port is a "TTL level" port (3.3V level), and will not work directly towards your PC without a 3V TTL - RS232 converter. You can either build something yourself (i.e. using something like the Maxim MAX3232 IC). Make sure to select one working with 3.3V, since some of them only work with 5V power supply.
The other (easier) option is to buy a ready-made converter board. A quick google search:
http://www.futurlec.com/Mini_RS232_TTL_3V.shtml
I also found one that looks nice at ebay:
http://cgi.ebay.co.uk/RS232-to-3-3-Volt ... dZViewItem
EDIT: A bit expensive though.
(This one needs 5-20V power supply, this is available on the board at the disk connector).
Note that I haven't ordered from any of those, and can't make any promises on their behalf.
Anyone know of other vendors?
So, do like this:
1) Remove the four hex screws on the rear panel.
2) Remove the rear panel, and gently slide the board (and disk) out of the case. If it's tight, loosen the four screws at the front as well. It is safe to pull at the USB connectors.
3) Now the board is exposed. The connector pads are located near the side of the board:
EDIT: (The image is for Bubba rev B board. The same things will work at the rev A board, but some details in the image may differ. For example, the resistor R79 next to the connector (J2) is only present in the rev B board. )
4) The signals:
Solder wires directly to the pads on the board, or, use a connector in between (the Harwin M50-3150522/M50-3500542 will fit, available from Farnell, art. no: 3078190 and 1022305). Be careful when soldering, if you heat up the pads too much, they may release from the board. Connect RX to the adapters TX (Tx from the PC to Rx on Bubba), and vice versa.
5) Connect the serial cable to your PC, and start a terminal program (such as windows HyperTerminal). Set your COM port to 115200 bps, 8,0,1. No hardware handshake.
6) Start your Bubba. The Linux boot log should appear in Hyperterminal. When booted, you'll get a login prompt. Just login as root (password is excito if you haven't changed it), and you're done!
Other useful links:
http://www.interfacebus.com/RS232_Pinout.html
http://www.farnell.com/
Please let me know if any information is missing, or if you have ideas on how to make this easier.
Good luck!