I had too much trouble, unfortunately, trying to bind the libhackrf functions directly to Racket functions with the FFI interface. The two hold ups were (1) I discovered I wasn’t actually supposed to be doing I/O inside a callout function using async-apply, and was having trouble trying to set up some kind of thunk queuing system instead; (2) for some reason the hackrf_stop_rx function would always hang when called from within Racket. On the second problem, I didn’t really have any way to debug the issue, but it looked liked pthread_join was not finishing from inside hackrf_stop_rx, perhaps something to do with the async-apply mechanics.
Feeling like I didn’t have way to move forward, because I don’t know how to debug C functions called from Rcket, I instead decided to back up and change my approach. Instead, I’m just going to use a separate small C program “kernel” to call the libhackrf functions, and communicate with that over named pipes. C programming is a lot of work, but I’ve gotten as far as writing the code in the kernel that creates the pipes and pulls a line from the input control pipe. There are four pipes: control input, control output, data input, and data output.
git clone git://git.librehacker.com/pub/git/hackrf-rkt.git