One inexpensive solution is to do what you suggest by using a set of PIC =
microcontrollers, and have them network the multiple serial ports =
together. To my knowledge there are no microcontrollers with more then 2 =
serial UARTs. So, this might be hard to do:
[pocket pc] ---> PIC ---------> device1
\--> PIC ----> device2
\--> PIC ---> device3
\---> PIC ---> device4
There are two better alternatives. First you could get some software =
UART code (basically use GPIOs as 3.3v serial ports, you only need 3 =
GPIOs to emulate a true Asynchronous serial port (Rx,Tx,Gnd)). Or =
consider using SPI to talk to a bank of Max3100s (UART<->SPI chips):
[pocket pc] ---> PIC ---(SPI)---> MAX3100 ---> device1
---> MAX3100 ---> device2
---> MAX3100 ---> device3
---> MAX3100 ---> device4
SPI allows multiple devices to share the same bus. You just need a GPIO =
for each slave device to select it. The Max3100 comes in a 16 pin QSOP, =
or 14 pin DIP package, and does require a crystal. The 3100 runs $7 from =
Digikey.
-Paul
R. Paul McCarty
Vitronics Inc
tel: (732) 389-0244 x30
fax: (732) 544-9431
-----Original Message-----
From: Carl Nilsson [mailto:
]
Sent: Monday, April 19, 2004 6:52 PM
To: 
Subject: RE: Multiple serial ports for Pocket PC?
I haven't checked out this yet. I presume you are telling me that TDK =
make a Bluetooth ... Serial Module (BISM ?) for $70. That's getting =
closer to the mark, but the problem there is each serial line needs one =
so I am up for, say, 4 X $70. Not out of the question. I appreciate =
the info on Bluetooth, about which I know next to nothing. I also know =
that I should look into it soon! A mixed approach might be to use a =
PIC microprocessor or two to collect all the serial lines running at =
9600 baud or less, put them out as one serial stream and then use a BISM =
or two.
Thanks, Carl
At 02:08 AM 4/20/04, you wrote:
TDK BISM $70
=20
Check out http://www.tekgear.com/category.cfm?category=3DBluetooth%20OEM =
for more OEM modules that might do the trick as well.
=20
Remember that the Bluetooth SPP Profile will only support a certain =
number of concurrent Serial Connections. I believe the limit is 4 =
concurrent connections with 7 devices that can be discovered. This =
means that there is a limit to how many devices you can poll at one =
time. If you want to poll a different device that is not in your list of =
4 active devices, you software has to drop one of the connections and =
pair up with the new device you want to poll. Keep this in mind when =
selecting Bluetooth as an alternative to wired connections.
=20
-Tony
-----Original Message-----
From: Carl Nilsson [mailto:]=20
Sent: Saturday, April 17, 2004 5:44 AM
To:
Subject: Re: Multiple serial ports for Pocket PC?
G'Day Ralf:
Thanks for your considered replies. I'm using an iPAQ h 2115 at the =
moment which does have Bluetooth. Haven't tried it yet and I'm a bit =
wary of possible interference from airport radar etc in an aircraft and =
interference to other devices in the aircraft, but it is certainly worth =
looking into. Don't know till you try things. Thanks for the TDK =
suggestion - depends on price. I would need one of these adapters for =
each device.
Carl
At 08:19 PM 4/17/04, you wrote:
Hello Carl,
thinking about your application scenario again I considered another=20
solution that might be easiest to deploy.
It uses Bluetooth - either your PDA is already equipped with it - or you =
may use a CF BT card.
For your serial data sources =3D> you may use a module that does a =
serial=20
cable replacement over BT. The most compact one that I'm aware of (and=20
that I actually use sucessfully) is a module made by TDK
=
http://www.tdksystems.com/tdk_bluetooth/bluetooth_serial_module.asp
Software on your PDA will let you set up multiple serial connections =
over=20
Bluetooth in parallel (at least with a PDA running Linux and the Bluez =
BT=20
stack). Your application on the PDA can then individually cope with the=20
data coming from each source.
Maybe that is an approach for you.
Regards
Ralf
---------------------------------------------------------------
Dr. Ralf Ackermann _ 
Multimedia Communications |/ | | |\/| Merckstrasse 25
|\ |_| | | 64283 Darmstadt, Germany
Tel.: (+49) 6151 16-6138 Fax: (+49) 6151 16-6152
---------------------------------------------------------------
http://www.kom.tu-darmstadt.de/~rac
---------------------------------------------------------------
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Carl Nilsson
137 Gordons Hill Road
Lindisfarne
Tasmania 7015
Australia=20
Carl Nilsson
137 Gordons Hill Road
Lindisfarne
Tasmania 7015
Australia=20
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