[maemo-developers] Unable to write to the serial port /dev/ttyS0 using QextSerialPort on Maemo device

[From: Ian Stirling]

Suyash.Kumar at tieto.com wrote:
> OK, I understood, Thanks for the explanation Denis but I have one more question? 
> IWe decided this approach as we have already implemented serial communication of Nokia N95 and PC (connected via USB cable). We simply used the symbian APIs for writing the information to the COM1 port and received the same on the windows PC's COM1 port and read it from there thus establishing a successful serial communication.
> 
> That's why I was trying the same for Maemo. The serial port is not visible physically on N95 also but somehow we managed the serial communication between device and PC using this approach.
> 
> Also, if the serial communication is not possible in this way, can you suggest me some other way/ sample code to achieve the same.
> 
That wasn't really USB, it was RS232, with a wierd connector.

There are some RS232-over-USB-port capable phones - but absolutely no 
desktop hosts support this.

Serial (RS232) and Universal Serial Bus - have about as much in common 
as man and manatee.

You need to configure the n900s USB port to emulate a RS232->USB 
converter - in some way.
http://www.kernel.org/doc/Documentation/usb/gadget_serial.txt is an 
overview of how it would be setup.

Unfortunately, I'm unaware of how this would interact with the default 
process that enables the requisite USB drivers.

I know hald-addon-usb-cable monitors the lowest level of this, and sends 
an event on dbus, but I'm unsure what watches for this event, and 
configures USB gadgets.