Xilinx / Xilinx/Embedded-Design-Tutorials

cdma_app.c does not work correctly

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Description

I've been following the Zynq-7000 SoC Embedded Design Tutorial (2023.2) using a Digilent Zybo Z7-20. The cdma-app showed FAIL even though the DMA transfer occurred (I used the Memory inspector to read 0x2000_0000 (the source) and 0x3000_0000 (the destination). I root caused the problem to the buffer compare where it appears that 256 bytes were being compared (Length=64*sizeof(u32)) even though only 64 bytes were transferred in the DMA transfer.

The fix was pretty easy once I figured out so I thought I'd share. The problem was in the SrcPtr and DestPtr declarations. I changed the declarations as shown:
// Changed from original code to fix pointer references
u8
SrcPtr = SourceAddr;
u8
DestPtr= DestAddr;
// end changes

Both the source and destination buffers were defined as u8 in the version of the app that I downloaded so now SrcPtr and DestPtr can access the u8 "array".
Roy

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in cdma_app.c, focusing on the SrcPtr and DestPtr declarations, the DMA transfer length, and the buffer comparison. Confirm how the source and destination buffers are declared and how the comparison length is calculated. Done means the application reports a successful comparison after transferring 64 bytes, using the issue's described pointer declarations.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
embedded-iot
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
55/100

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