Project Peacock

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Project Peacock will be (in theory) a chipset for doing graphics display output from a microcontroller.

  • Concept 1 - DVI/VGA - Hard MCU for I/O, CPLD for high speed graphics output
    • Display Controller MCU
      • Communicate with host via I2C/SPI/RS232
      • Will need a lot of I/O pins
        • RAM address bus - 22 pins
        • RAM data bus - 16 pins
        • RAM arbitration/handshaking - 6 pins
        • SPI/I2C/RS232 - 4 pins
        • Rough total - 48 I/O pins required
      • PIC32MX575F512H seems a good fit, and keeps commonality with another project (BIRD)
    • Display Driver CPLD
      • Essentially just the digital part of a RAMDAC, constantly reads data from the RAM and spits it out to the output converter
      • Since it's dealing with RAM anyway, it can handle the RAM details for the MCU (accept raw data from the MCU and write it to memory)
      • Using a CPLD means the Display Controller MCU doesn't need to be super-fast
    • RAM
      • SRAM
        • Far too expensive (~$200) for the amount needed
      • PSRAM (Pseudo SRAM)/CellularRAM
        • SRAM interface but DRAM backend, simple to interface with and cheap (~$6)
        • Only available in VFBGA package meaning a four-layer board would be required, and hard to solder
      • SDRAM
        • Inexpensive (~$5) and readily available
        • Easy non-BGA SMT packages
        • Harder to interface with, would need to have the CPLD handle RAM refreshing and other housekeeping
    • Output converter
      • TMDS converter for DVI
      • DAC for VGA
  • Concept 2 - DisplayPort/DVI/VGA - Soft MCU (in the FPGA) for I/O, FPGA for high speed graphics output/SDRAM interfacing
    • Everything in one chip makes board layout easier, is smaller, and could actually be less expensive given how small some softcores are
    • Could do DisplayPort output if proper transceivers are used, which would be much more future-proof than other solutions
      • The Arria II GX and Cyclone IV GX series both have these transceivers
        • Arria II GX starts at >$400!
        • Cyclone IV GX 15k LE model starts around $26
          • Available in a weird dual-row QFN (EP4CGX15BN11C8N) or in an FBGA (EP4CGX15BF14C8N)
          • Datasheet says the QFN version is only for boards < 0.8mm thick for some reason
    • Could use DisplayPort->DVI/VGA interface chips to support VGA or DVI output
      • DisplayPort->VGA seems to be available
      • For DisplayPort->DVI the only option is the Parade PS161 chip, which is only available in qty 100k (!)
    • Looks like the chip will need to output DVI/HDMI and/or DisplayPort then, and one of those can be converted to VGA if needed
  • Concept 3 - DVI/HDMI/VGA - Soft MCU (in the FPGA) for I/O, FPGA for high speed graphics output/SDRAM interfacing
    • Everything in one chip makes board layout easier, is smaller, and could actually be less expensive given how small some softcores are
    • DisplayPort is very complicated, so working on this concept first probably makes sense
      • This concept also doesn't require a transceiver-equipped FPGA so should in theory be a bit cheaper
        • But it does need a TMDS converter on the output
    • Cyclone III around 10-15k LE probably makes the most sense for this one
      • The Spartan 6 has built in TMDS support, so that chip might actually make more sense
        • 9k LEs for ~$18, 14k for ~$25
    • Not sure how HDMI licensing/royalties work, if at all possible it would be very good to support it
      • Looks like it doesn't apply to chips, only sold-to-consumers end products
      • HDMI 1.3a spec is free to download, 1.4 spec is only available to HDMI Adopters