Legal stuff

I've shamelessly stolen this content from beecon.de. The information about the authors name is from Albert's mod. I've tried to contact beecon.de but I didn't get any response.

Introduction

The SLC version of the Siemens SIMpad was being delievered with a built-in DECT module to allow wireless internet access via the european cordless telephone standard (DECT).

With bluetooth and WLAN, faster and more popular wireless data transmission technology is available. The SIMpad has a PCMCIA slot which can be used with standard WLAN cards. Unfortunately, this prevents the usage of the PCMCIA slot for other purposes like e.g. a memory card or microdrive. Furthermore, a WLAN pcmcia card draws a significant amount of current.

These instructions show how to replace the internal DECT modem with a bluetooth interface leaving the PCMCIA slot free for other purposes and needing far less energy than a WLAN card.

Currently only linux supports this setup.

News

9/20/04: The bluetooth interface is working with openembedded and connecting to the internet via a bluetooth access point (e.g. the MicroBAP) is possible. The bluetooth modules power supply is automatically controlled and e.g. a network connection can be re-established after suspend. We hope to get all the necessary kernel and application patches included in the oe branch soon and be able to provide a ready-to-run linux image. 9/13/04: It has been verified, that the bitrate limitation to 230kbit/s is not caused by the 1k series resistors in the serial data and control lines. It's still unclear why bytes are being lost at higher bit rates.

Hardware setup

Figure 1: The hardware setup higher resolution

The hardware consists of only two new parts to be inserted into the SIMpad. See this page for a snapshot of the inards of a SIMpad. The DECT connector is placed in the lower left corner. By removing the flat cable, the DECT modem can easily be disconnected.

Figure 1 shows the setup of the new bluetooth interface. It consists of two parts only: The bluetooth module itself and a MAX 8881 3.3V voltage regulator. This regulator reduces the 5V being used for the DECT module to 3.3V as required for the bluetooth module. Furthermore, with its shutdown feature, the mechanism that was used to switch the DECT modules power on and off can be used for the bluetooth module as well. This is very handy, if the bluetooth module is in unknown state. The software might then reset it just by switching its power off and on again.

The module itself uses 3.3V on all signals lines. So does the SIMpad. In order to avalid problems with the 5V of the DECT module, the SIMpad has series resistors in all serial interface lines going to the DECT connector. The bitrate is limited to 230400 bit/s. Higher bitrates are very unreliable.

Figure 2: Prototype hardware higher resolution

Figure 2 depicts the prototype hardware solution.

Linux software setup

Since the bluetooth module is connected to the second serial port of the SIMpads SA-1110 CPU, using bluetooth requires a working software driver for /dev/ttySA1. The 2.4.18 kernels of opensimpad 0.8.0 do not work. Instead a 2.4.25 from openembedded.org should be used.

The first step in using the module is to apply power to it. This is done via the proc interface to cs3. This is a general purpose port used for various settings inside the SIMpad. Use cat /proc/cs3 to read its state. Use echo "0xd51a" >/proc/cs3 to switch bluetooth power on and echo "0xd41a" >/proc/cs3 to power it off.

Then load the bluetooth driver hci_uart.o. This is not installed in the default setup and you might have to install it manually. You can then attach the bluetooth module with hciattach /dev/ttySA1 csr 230400. If everything is fine, the CSR chip id should be displayed. You can now use all the linux bluetooth software to establish network connections (using pand), use bluetooth keyboards (using hidd) etc etc. The opie bluetooth manager for the zaurus works on the SIMpad as well and will give you access to some of the basic bluetooth configuration.

Caveats

The cs3 control port is used by other parts of the system as well. Some of these parts obviously don't care about the current state and e.g. booting opie will disable power for the bluetooth module and the module has to be reinitialized.

The SIMpads init scripts and the like are not yet prepared to cope with bluetooth and e.g. bnep network connections. Hopefully this will be fixed soon.

To do

• check the stuff about openembedded.org kernel and if the familar kernel fit as well.
• get rid of the news section