USB to RS232 Adapters

Author:  Jonathan Davies

This page describes how to get an AlphaMicro Components RS232 to USB converter (model AMC-232USB01) working under Linux.

 http://www.cl.cam.ac.uk/Research/DTG/p/research/attachment/wiki/USBtoRS232/amc232usb01.png?format=raw

The adapter cable contains a Future Technology Devices International (FTDI) FT232BM-compatible chip. See  http://www.ftdichip.com/Products/FT232BM.htm for further details.

Unfortunately, the FTDI driver supplied with Linux 2.6.11 is not compatible with this particular cable: it does not recognise the device ID, 0xFF00, as being an FT232BM-compatible device. The attached patch addresses this issue. The patch can be applied as follows:

cd /usr/src/linux/drivers/usb/serial
patch -p1 < ftdi-sio-amc232usb01.patch

Once the patch has been installed, the ftdi-sio module should be recompiled:

cd /usr/src/linux
make && make modules_install

And finally the module can be inserted using:

modprobe ftdi-sio

When the adapter cable is inserted, dmesg reports:

usb 1-4.3: FTDI FT232BM Compatible converter now attached to ttyUSB0

Now, the device /dev/ttyUSB0 will behave like any other serial port device.