Serial Port
From OESF
Copied from the zauruszone wiki
Contents |
Zaurus serial port access
The "Sharp I/O" port at the base of the Zaurus is a serial port. It can be accessed from Linux as usual, as /dev/ttyS0.
For a complete specification of the serial interface, see Sharp's hardware document:
http://www.sharp.de/pdat/sio.zip
This link is not broken thanks to smurfix
Accessing /dev/ttyS0
The Z will take it over ttyS0 and try to run pppd on it (this does not apply to the 3.10 version of the Sharp ROM, only the 2.xx versions). In the Sharp ROMs attempts to kill it will cause it to be respawned, as this appears in /etc/inittab. It can also be avoided by rebooting the Z ("reboot" in the terminal window, or use the Shutdown app) and pressing the "/?" key as soon as you see "Wait..." during reboot, and then pressing the "E" key. Of course, you'll need to do this every time you reboot if you don't change /etc/inittab.
The offending line in /etc/inittab is:
pd:5:respawn:/etc/sync/serialctl
Using vi or something to add a pound sign (#) in front of this line disables the respawning. /etc/sync/serialctl is the script that launches pppd - you can also comment out the pppd line here and replace it with something like sleep 36000. You may have to reboot after making this change for it to be effective.
Once the serial port is available you can access the serial port using serial terminal, gps programs, pppd dialing a cell phone (I connect to the 'net with Nextel's phones, Sprint PCS with an LG 5350 and serial module also works), etc. You will need a null modem and gender bender, or a cable mod, to talk to other devices that normally connect to a PC, like modems, GPS receivers, etc.
There is alread a prepararion by Sharp for this, use runlevel 3. Further information at: http://www.sc-systems.com/info/zaurus/notes/Init3Mode.html
If you need to confirm input on the serial port (for instance, testing a serial GPS or phone hookup), issue the following from a command prompt:
# stty 4800 -F /dev/ttyS0 # cat /dev/ttyS0
(Note the baud rate may vary depending on the device you are connecting. Also the stty command will have to be issued any time you reboot.) This will show all incoming text on the line. Pressing "Function C" will terminate the output. This data may also be sent to a capture file:
# cat /dev/ttyS0 > mydata.txt
Buying a serial-to-Sharp cable
The Sharp CE-170TS cable works on the Zaurus. It has electronics in it, not just a pin mapping. The Zaurus end is a large box with a power connection that blocks the keyboard so that it cannot be opened with the cable attached. The box is glued together. Removing the outside of the box is still not enough clearance. If the power connector were desoldered from the internal circuit board then there should be enough clearance (see below.)
This cable comes with a DB-9 female so that it can be plugged into a PC, upon which the Zaurus acts like a DCE (see cable diagram above.) If you want to hook it up to another DCE (such as a modem or GPS receiver) you will need to insert a gender bender (DB9 male-to-male adapter) and a null modem (DB-9 male-to-female adapter that swaps pins to turn a DCE into a DTE or vice versa.) Both of these are available at Radio Shack.
One funny thing about the commercially available Sharp serial cable (part number CE-170TS) when running on the SL-5000D is that even when the Z is off, there is signal on the Z's serial data output line (this would be RxD, or pin 2 on the DB-9 end of Sharp's data cable). Although I have not tested this, it suggests that if you leave the Z plugged into a device, you will eventually drain its battery. It appears that only the serial data output line does this; the other handshake output lines do not do this! SL-5500 owners, is this the same for you?
Note: The Sharp Zaurus and the connector only provides TTL or CMOS voltage and current levels out the serial port. Some equipment requires bipolar (<-3v or >3v) signal levels to be valid, typically for power or a wake up function. (Example: the $99 GPS receiver available at Radio Shack, see below.) Some also require a certain amount of current sourcing or sinking. The Sharp serial connector will NOT work with such devices, since its current output is lower than typical RS-232 and signal low is zero volts rather than a negative voltage.
However, it should work with most devices, since modern RS-232 receiver chips are designed to have a signal low threshold of about 1 volt and a signal high threshold of about 2 volts. This makes the Z's "RS-232" output signal, which swings from 0 to 3.3v (or 0 to 3.3v) work just as well as if it swung from -12V to 12V.
Building a serial-to-Sharp cable
(The Sharp development team says this will be available in early 2002, but in the meantime...)
To go to a standard 9 pin serial such as you would find on a PC you would use the following pin config.
Although the Zaurus is a computer, the Sharp cable, and this diagram, treats it as a DCE rather than DTE (which a PC normally is.)
Wiring for hookup to a DTE (ie, a PC)
(Zaurus as DCE) (same as Sharp's CE-170TS)
Female
DB-9 Signal name Signal
9 pin (relative Direction
zaurus serial to PC) Z (DCE)----- PC (DTE)
-------------------------------------------------
3 3 TxD <-
4 2 RxD ->
5 7 RTS <-
6 8 CTS ->
7 6 DSR ->
8 5 GND --
14 4 DTR <-
Wiring for hookup to a DCE (ie, a modem or GPS receiver)
(Zaurus as DTE)
Male
DB-9 Signal name Signal
9 pin (relative Direction
zaurus serial to Z) Z (DTE)----- modem (DCE)
-------------------------------------------------
3 2 RxD <-
4 3 TxD ->
5 8 CTS <-
6 7 RTS ->
7 4 DTR ->
8 5 GND --
14 6 DSR <-
- NOTE: The second table was derived from the first, and may contain mistakes. Would the first person making a cable to the second table verify that this table is indeed correct, and if so, delete this note.
The tough part will probably be getting the proprietary connector. You will need part # TCX3106 made by Hosiden Corp http://www.hosiden.co.jp
Their Californian Sales office is 1-408-252-0541 Or if you are feeling particularly resourceful you could 'borrow' the connector from the docking station :-)
(posted by Martin Dorschler) (edited by someone else)
(This appears to be an order page for Japanese products for Zaurus connectivity. Translation via Babelfish.)
