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Continuous/Self-perpetuating eDMA scatter gather

Question asked by Ryan Shuttleworth on Jan 30, 2018
Latest reply on Aug 1, 2018 by CUSTOMER CUSTOMER

Hello, I am using IAR with an RT1050 SDK, version  2.3.0 (2017-11-16).   Is there a way to make scatter gather eDMA transaction self-perpetuating, i.e. they require no software intervention to keep the transactions running indefinitely? 


I have been working with the SDK scatter gather example and they appear to always stop after the last TCD even when linking appears to be set up correctly in the last TCD.  There are some hints in the reference manual and API code that suggest this is expected behavior then other still suggest it is not.


Here is a comment in the API documentation that suggests this might not be possible:


For the last two continuous ISRs in a scatter/gather process, they both load
the last TCD (The last ISR does not load a new TCD) from the memory pool to the
eDMA engine when major loop completes. Therefore, ensure that the header and
tcdUsed updated are identical for them. tcdUsed are both 0 in this case as no
TCD to be loaded.