SD Card Controller written from scratch in SystemVerilog

SD Card CMD0 in action (first step in init process)

LEDs on the FPGA show the response from SD card

• 0xFF is empty response
• 0x01 is idle card response (means card responded and ready for initialization)

Repo Structure

• SystemVerilog source files (src)
• Reference and scratch files in Python, Markdown (ref)
• Test benches (test/tb)
• Top module for a Gowin 9K FPGA (fpga/gowin)

Architecture

• A low level half-duplex byte-oriented master SPI controller
• An SDIO controller that drives an SDIO device in SPI mode, uses SPI controller
• For future: A full SD card initialization SystemVerilog module or task

Testing

Currently only simple test benches, uses

• Low level half-duplex byte-oriented, command-oriented SPI slave controller
• A simple dummy SD card using slave controller to use inside test benches