cdma_app.c does not work correctly

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#52 opened on Aug 9, 2024 3 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 2/5
Estimated time: 1-3 hours
Newbie friendliness: 55/100

Issue type: Bug
Clarity: Clearly specified
Activity status: Stale
Tech stack: c
Domain: embedded-iot

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.

Description

bug

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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