cannot see RS232 serial data on Raspberry Pi [migrated]

cannot see RS232 serial data on Raspberry Pi [migrated]

I have a Model B Raspberry Pi and an Serial Pi RS232 Interface. I am
running Raspbian Wheezy on my RPi.
I configured the RPi using a Serial Guide, with particular attention to
the section titled "Reconfigure the RPi console port to to be used as a
standard serial port".
I used a null modem to connect a Windows PC to the RPi. The PC ran
TeraTerm and the RPi ran minicom. I configured both as follows:
Baud Rate = 115200, Data Bits = 8, Parity = NONE, Stop Bits = 1, Flow
Control = NONE
This worked perfectly in both directions.
I need to log the data, I assumed something like this would work:
cat /dev/ttyAMA0 > /var/log/ttyAMA0.log
But it doesn't log anything. I tried just this, and nothing is output to
the screen:
cat /dev/ttyAMA0
Does anyone have any ideas or suggestions?