My attempt to multi-thread an audio talk-though program using batches of data M. Smith Electrical and Computer Engineering University of Calgary, ucalgary.ca

Laboratory 5 – Done in “C and C++” Stage 1 – 30%  Develop and investigate a multi-tasking system where the threads are free-running. Thread tasks are “Sleep(time_task)”  Develop and investigate a multi-tasking system where the threads communicate through semaphores to control order of operation Stage 2 – 55%  Demonstrate and investigate turning an “audio – talk-through program” into a multi-threaded system – one point processed per interrupt Stage 3 – 15%  Demonstrate a batch processing system as a multi-threaded system Options  Use SHARC ADSP boards (40 MHz) – existing audio-libraries – have not attempted  Use Blackfin ADSP-BF533 boards (600 MHz) – existing audio-libraries – have been successful at home, but not here  Use Blackfin ADSP-BF533 boards (600 MHz) – using very simple, no frills, audio-talk though library – surprising simple with 1 to 32 points being processed. Fails with 33 points. Code logic issue, not a timing issue as I can waste cycles per block at 32 points

Implementing a multi-thread system -- Laboratory 5 – Part B concepts Collect 1 44 kHz  array1 Collect 1 44 kHz  array2 Collect 1 44 kHz  array3 Collect 1 44 kHz  array1 Collect 1 44 kHz  array2 Move array1  array4 SimulateComplex Move array2  array5 SimulateComplex Move array3  array6 SimulateComplex Move array1  array4 SimulateComplex Transmit N 44 kHz  array4 Transmit N 44 kHz  array5 Transmit N 44 kHz  array6

Final ReadThread – Single Point

Final ProcessThread – Single Point

Final WriteThread – Single Point

Read Thread – ISR driven

Thread Status History – ISR driven

Laboratory 5 – Done in “C and C++” Stage 1 – 30%  Develop and investigate a multi-tasking system where the threads are free-running. Thread tasks are “Sleep(time_task)”  Develop and investigate a multi-tasking system where the threads communicate through semaphores to control order of operation Stage 2 – 55%  Demonstrate and investigate turning an “audio – talk-through program” into a multi-threaded system – one point processed per interrupt Stage 3 – 15%  Demonstrate a batch processing system as a multi-threaded system Options  Use SHARC ADSP boards (40 MHz) – existing audio-libraries – have not attempted  Use Blackfin ADSP-BF533 boards (600 MHz) – existing audio-libraries – have been successful at home, but not here  Use Blackfin ADSP-BF533 boards (600 MHz) – using very simple, no frills, audio-talk though library – surprising simple with 1 to 32 points being processed. Fails with 33 points. Code logic issue, not a timing issue as I can waste cycles per block at 32 points

Implementing a multi-thread system -- Laboratory 5 concepts Collect N 44 kHz  array1 Collect N 44 kHz  array2 Collect N 44 kHz  array3 Collect N 44 kHz  array1 Collect N 44 kHz  array2 Move array1  array4 SimulateComplex Move array2  array5 SimulateComplex Move array3  array6 SimulateComplex Move array1  array4 SimulateComplex Transmit N 44 kHz  array4 Transmit N 44 kHz  array5 Transmit N 44 kHz  array6

Read – Handling 4 points No-audio intention – just see if it will work test

Process – Handling 4 points No-audio intention – just see if it will work test

Write – Handling 4 points No-audio intention – just see if it will work test

Nett Result Not working as expected – equal priority (5) on each task We are obviously missing samples

Changing Priorities Priorities ReadThread 3 -- obviously the most critical ProcessThread 5 WriteThread 5

Different Priorities Priorities ReadThread 3 -- obviously the most critical ProcessThread 5 WriteThread 4

No idle time available – Optimize the code Priorities ReadThread 3 ProcessThread 5 WriteThread 5 Priorities ReadThread 3 ProcessThread 5 WriteThread 4

Implementing a multi-thread system -- Laboratory 5 Collect N 44 kHz  array1 Collect N 44 kHz  array2 Collect N 44 kHz  array3 Collect N 44 kHz  array1 Collect N 44 kHz  array2 Move array1  array4 SimulateComplex Move array2  array5 SimulateComplex Move array3  array6 SimulateComplex Move array1  array4 SimulateComplex Transmit N 44 kHz  array4 Transmit N 44 kHz  array5 Transmit N 44 kHz  array6

Problem – NOT coding what we intended Collect N 44 kHz  array1 Collect N 44 kHz  array2 Collect N 44 kHz  array3 Collect N 44 kHz  array1 Collect N 44 kHz  array2 Move array1  array4 SimulateComplex Move array2  array5 SimulateComplex Move array3  array6 SimulateComplex Move array1  array4 SimulateComplex Transmit N 44 kHz  array4 Transmit N 44 kHz  array5 Transmit N 44 kHz  array6

Proper Code

Net Result TOTAL SYSTEM HANG BLOCKED SEMAPHORES

Tried a number of things Worked out which semaphore was blocking Different priorities Different TIC times Better – but obviously missing cycles – particularly write

Decided to tie WriteThread to interrupt as well as ReadThread

Final Test Result Seems to behaving as expected However – when changed MAXIMUM COUNT FOR READ / WRITE ISR Semaphores – status history changes This could indicate that missing some interrupts Could mean nothing – interrupts asynchronous to timer TICs

Could handle 800 waste “times” every 32 samples – plenty of time cycles + Inner loop =2 * BUFFERLENGTH Outer loop = Wastetime * (3 + INNER) Total = 13 + Inner loop BUFFER = 32, waste time = 800 Cycles around 800 * 64 = K Blackfin SHARC D0 (8) R0 (16) R0 A0 (6) P0 (with a bit of MIPS) (6) I0 (4) I0 (16)

Real life test -- small buffers Absolutely nothing However  4 audio connections in  6 audio connections out Got the correct connections  Set buffer = 1 – worked first time  Set buffer = 32 – worked first time

Larger buffers BUFFERSIZE – 64 – out of bsz memory error Fix.LDF file – manually (GUI window works how?) MEMORY { mem_VDK_strt { TYPE(RAM) START(0xFFA00000) END(0xFFA00003) WIDTH(8) } mem_l1_code { TYPE(RAM) START(0xFFA00004) END(0xFFA0FFFF) WIDTH(8) } mem_l1_code_cache { TYPE(RAM) START(0xFFA10000) END(0xFFA13FFF) WIDTH(8) } mem_EVT_all { TYPE(RAM) START(0xFF900000) END(0xFF900003) WIDTH(8) } mem_EVT_NMI { TYPE(RAM) START(0xFF900004) END(0xFF900007) WIDTH(8) } mem_EVT_EVX { TYPE(RAM) START(0xFF900008) END(0xFF90000B) WIDTH(8) } mem_EVT_IRPTEN { TYPE(RAM) START(0xFF90000C) END(0xFF90000F) WIDTH(8) } mem_EVT_IVHW { TYPE(RAM) START(0xFF900010) END(0xFF900013) WIDTH(8) } mem_EVT_IVTMR { TYPE(RAM) START(0xFF900014) END(0xFF900017) WIDTH(8) } mem_EVT_IVG7 { TYPE(RAM) START(0xFF900018) END(0xFF90001B) WIDTH(8) } mem_EVT_IVG8 { TYPE(RAM) START(0xFF90001C) END(0xFF90001F) WIDTH(8) } mem_EVT_IVG9 { TYPE(RAM) START(0xFF900020) END(0xFF900023) WIDTH(8) } mem_EVT_IVG10 { TYPE(RAM) START(0xFF900024) END(0xFF900027) WIDTH(8) } mem_EVT_IVG11 { TYPE(RAM) START(0xFF900028) END(0xFF90002B) WIDTH(8) } mem_EVT_IVG12 { TYPE(RAM) START(0xFF90002C) END(0xFF90002F) WIDTH(8) } mem_EVT_IVG13 { TYPE(RAM) START(0xFF900030) END(0xFF900033) WIDTH(8) } mem_EVT_IVG14 { TYPE(RAM) START(0xFF900034) END(0xFF900037) WIDTH(8) } mem_EVT_IVG15 { TYPE(RAM) START(0xFF900038) END(0xFF90003B) WIDTH(8) } mem_sysstack { TYPE(RAM) START(0xFF90003C) END(0xFF90083B) WIDTH(8) } mem_l1_data_b { TYPE(RAM) START(0xFF90083C) END(0xFF903FFF) WIDTH(8) } mem_l1_data_b_cache { TYPE(RAM) START(0xFF904000) END(0xFF907FFF) WIDTH(8) }

Memory issues – on 64 point data batches Still did not work  Did I change the memory map correctly?  No – seems okay as works with 32 – but perhaps having caching issue Went back to old memory map  Went to configure external SDRAM and use that  Modified only 1 array – left channel Left channel fails – right channel works Spending too much time in context switching  Group ReadThread and WriteThread code together  Does not even work with 32 !!!!!! Am convinced that there is a logical issue associated with the semaphore handling.

Bonus – 20% bonus If you can get all parts of Lab. 5 running and then solve this issue of why fails at 64 points (even when not wasting cycles) – 20% bonus on this lab. marks and either a mention or a “co-author-ship” on one of the Circuit Cellar articles May even be worth some money if I manage to sell the articles