Incomplete buffers from PRU

[geissdoerfer]

It has been reported that the during emulation, the PRU reports an incomplete buffer exception. This exception is raised in the PRU1 firmware before returning a buffer to the host, when it detects that less than the planned number of samples have been taken and written to the buffer. The error is sporadic and has not been observed during tests. I expect the tests to fail, if it occurs. This should be investigated. A first step is reproducing the issue, potentially by creating adverse synchronization conditions, i.e. strong drift between Linux host clock and PRU clock.

[orgua]

seems to be solved with v0.2.3 but remains under observation. previous code was likely to cause race conditions and buffer overflows