188
188
The DMA addresses are limited to 32 bits (~4GB for everything). This means we
189
can't really use DMA pages are sole buffers. Therefore,
190
1. In streaming mode a second thread will be spawned copying the data from the
191
DMA pages into the allocated buffers. On duration expiration this thread
192
will be stopped but processing will continue until all copyied data is
193
passed to the callbacks.
194
2. In synchronous mode, a single event will be extracted from the the DMA
197
- Actually, we can make another in-module buffering. But this hopefully can
189
can't really use DMA pages are sole buffers. Therefore, a second thread, with
190
a realtime scheduling policy if possible, will be spawned and will copy the
191
data from the DMA pages into the allocated buffers. On expiration of duration
192
or number of events set by autostop call, this thread will be stopped but
193
processing in streaming mode will continue until all copyied data is passed
196
To avoid stalls, the IPECamera requires data to be read continuously read out.
197
For this reason, there is no locks in the readout thread. It will simplify
198
overwrite the old frames if data is not copied out timely. To handle this case
199
after getting the data and processing it, the calling application should use
200
return_data function and check return code. This function may return error
201
indicating that the data was overwritten meanwhile. Hence, the data is
202
corrupted and shoud be droped by the application. The copy_data function
203
performs this check and user application can be sure it get coherent data
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There is a way to avoid this problem. For raw data, the rawdata callback
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can be requested. This callback blocks execution of readout thread and
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data may be treated safely by calling application. However, this may
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cause problems to electronics. Therefore, only memcpy should be performed
210
on the data normally.
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The reconstructed data, however, may be safely accessed. As described above,
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the raw data will be continuously overwritten by the reader thread. However,
214
reconstructed data, upon the get_data call, will be protected by the mutex.
201
217
Register Access Synchronization
added
removed
NOTES
