– – BlackAn –BlackAn –The Blackfin AnalyzerThe Blackfin Analyzer

by Jacob Zuraskyby Jacob Zurasky

and Paul Deffenbaughand Paul Deffenbaugh

Project GoalsProject Goals

Display oscilloscope view of audio on TV Display oscilloscope view of audio on TV screenscreen

Compute and display Fourier Spectrum on Compute and display Fourier Spectrum on TVTV

TasksTasks

Sample Audio DataSample Audio Data

Compute Fourier SpectrumCompute Fourier Spectrum

Update Video MemoryUpdate Video Memory

Display Video MemoryDisplay Video Memory

Displaying GraphicsDisplaying Graphics

Memory requirementsMemory requirements One Frame = [1716][525] elementsOne Frame = [1716][525] elements Two frames required to buffer video Two frames required to buffer video

outputoutput

Active area on TV is 310 x 212 pixelsActive area on TV is 310 x 212 pixels

Video MemoryVideo Memory SDRAM holds first frame at 0x0000 0000SDRAM holds first frame at 0x0000 0000

Second frame at 0x000D BF24Second frame at 0x000D BF24

DMA0 sends data through PPIDMA0 sends data through PPI

Video Codec creates the TV signalVideo Codec creates the TV signal

SDRAM ProblemsSDRAM Problems

Writing to SDRAM interrupts readingWriting to SDRAM interrupts reading

This causes video glitches This causes video glitches

Corrupts the timing of data sent to codecCorrupts the timing of data sent to codec

SDRAM SolutionSDRAM Solution

We found that 1-4 pixels can be writtenWe found that 1-4 pixels can be written

at the end of each TV line sentat the end of each TV line sent

This method allows for 525-2100 pixels This method allows for 525-2100 pixels toto

be written per frame sent to the TVbe written per frame sent to the TV

SDRAM SolutionSDRAM Solution

We changed the DMA0 interrupt to triggerWe changed the DMA0 interrupt to trigger

on the completion of inner loop (each line)on the completion of inner loop (each line)

State machine decides what pixels need to State machine decides what pixels need to be written and blanked at the correct timebe written and blanked at the correct time

State MachineState Machine

State 0 – Fill audio buffersState 0 – Fill audio buffers

Capture 310 audio samples at 48 kHzCapture 310 audio samples at 48 kHz

This is the width of the TV screenThis is the width of the TV screen

State is changed to 1 upon completionState is changed to 1 upon completion

State MachineState Machine

State 1 – Process audio dataState 1 – Process audio data

Compute the DFT if necessary for Compute the DFT if necessary for displaydisplay

Set to state 2 upon completionSet to state 2 upon completion

State MachineState Machine

State 2 – Plot data to video memoryState 2 – Plot data to video memory

At the end of each line sent, draw a new pixelAt the end of each line sent, draw a new pixel

to the video buffer not being displayedto the video buffer not being displayed

When all current plotting is complete, switch to When all current plotting is complete, switch to State 3State 3

State MachineState Machine State 3 – Swap Video BuffersState 3 – Swap Video Buffers

At the end of a complete frame (DMA outer loop), At the end of a complete frame (DMA outer loop), the DMA start address is set to the other video the DMA start address is set to the other video buffer in SDRAMbuffer in SDRAM

The switch must occur while the DMA is disabled and The switch must occur while the DMA is disabled and after completing a frameafter completing a frame

State MachineState Machine State 4 – Blank the previous video bufferState 4 – Blank the previous video buffer

The buffer not being displayed now must be cleared for The buffer not being displayed now must be cleared for new datanew data

Write black pixels over the old dataWrite black pixels over the old data

Reset back to State 0 Reset back to State 0

Sampling Audio DataSampling Audio Data

DMA1 uses SPORT0 to receive audio DMA1 uses SPORT0 to receive audio datadata

DMA2 uses SPORT0 to transmit audio DMA2 uses SPORT0 to transmit audio datadata

Sampling Audio DataSampling Audio Data

On interrupt, if State = 0, fill audio On interrupt, if State = 0, fill audio buffersbuffers

Audio_BufferL[] and Audio_BufferR[]Audio_BufferL[] and Audio_BufferR[] Collect 310 samples of audioCollect 310 samples of audio

Compute the DFTCompute the DFT

Using this definition, the DFT is Using this definition, the DFT is computedcomputed

Compute DFTCompute DFT

Sine and Cosine factors are pre-computedSine and Cosine factors are pre-computed

This greatly improved the speed of DFTThis greatly improved the speed of DFT

The lookup tables had to be implemented The lookup tables had to be implemented in SDRAMin SDRAM

Plotting Data to TVPlotting Data to TV

There are 4 display modesThere are 4 display modes Left channel oscilloscopeLeft channel oscilloscope Left/Right channel oscilloscopeLeft/Right channel oscilloscope DFTDFT Left channel oscilloscope and DFTLeft channel oscilloscope and DFT

Plotting Data to TVPlotting Data to TV

The data is scaled depending on the modeThe data is scaled depending on the mode

Data is plotted pixel by pixel at the end of Data is plotted pixel by pixel at the end of each line sent to the TVeach line sent to the TV

Video buffers are swapped once completeVideo buffers are swapped once complete

Changing Display ModesChanging Display Modes

Can only occur at the end of a frameCan only occur at the end of a frame

Both video buffers must be clearedBoth video buffers must be cleared

Then change the display mode flagThen change the display mode flag

Future ImprovementsFuture Improvements

Add a title screen from a bitmap imageAdd a title screen from a bitmap image

Fine tune the DFT results and scalingFine tune the DFT results and scaling

More display modesMore display modes

Questions?Questions?

Please email us atPlease email us at

jzurasky@fit.edu

pdeffenb@fit.edu