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Development stages

Roughly speaking, there are 4 stages - PoC, building an advanced adapter, creating flash chip emulation and creating an open-source FTL for block devices with raw NAND flashes.

It should be noted that the order of these stages could change if required or just so desired.

Proof-of-concept proxy & adapter

  1. Raw NAND initialization & I/O PoC over Olimex A20 Olinuxino board

  2. ufedm kernel module PoC

    • Basic functionality on top of nandsim
    • Tests with actual NAND hardware
    • Implemeting these set of features for advanced handling of NAND chips:
      • Passthrough mode: Skip userspace intervention (useful for tests and "pure-caching" mode)
      • Cache mode - keep a RAM-backed cache of a MTD device, so reading is fast I/O

  3. TSOP48 NAND Socket soldering & testing

    • Might require tweaking NAND flash controller timings

Build an advanced adapter (USB NAND flash controller)

  1. USB-to-NAND flash controller as a Linux MTD device (usbnfc)
    • Should use other board than the Olimex, maybe something that's not Linux!
    • A transparent "raw" NAND flash controller should be required
    • Probably requires a special kernel module for this to work
  2. Testing ufedm on top of usbnfc in various conditions.

At that point, there are many possibilities to build many adapters - something like an STM32-based solution with its FMC silicon, a prebuilt solution like SEGGER NAND flash evaluator board or maybe even an FPGA board.

Different adapters should allow supporting NAND flash chips with bus width of x8 or x16, a separate VCCQ from VCC input and different packages (TSOP56, BGA packages, etc) and SPI chips as well.

NAND flash chip emulation

  1. Creating gateware & firmware for emulating a NAND flash chip with adjustable parameters such as page geometry, internal ECC algorithm and in-page data layout, bus width and VCC inputs.

Building an open-source flash translation layer

Building a block device (USB thumb drive) with raw NAND flash and eMMC or MMC cards using an embedded NAND flash controller with appropriate firmware for a microcontroller, or maybe even gateware to speed things up with FPGA.

  1. USB to SPI/Parallel flash using an embedded microcontroller
  2. USB to eMMC flash using an embedded microcontroller
    • Mainly as a comparing reference to the raw flash variant.