Trying to read the data from an ASK RF transmitter
Assuming the signal is at logic levels, what you really want is a logic analyzer. These would provide you with bit value and timing information that would be easy to analyze. Given that this is only one pin, the options are greater. 

There are many inexpensive logic analyzers that you can connect to a PC, and in this case maybe even a Bus Pirate would work. 

However, given that this is very likely a slow signal, you have the option to build your own.  There might already be open source code that does what you want, but all you really need is to sample a port pin (or use a timing capture peripheral) and send the edge changes and their timing to a computer where you can reconstruct the signal and decode at your leisure. 

You could even use some software to convert your sound card into a slow oscilloscope/data capture device and then decide the signal by hand.