Project Peacock

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 LU 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 LU probably makes the most sense for this one
    • The Spartan 3A has built in TMDS support, so that chip might actually make more sense
  • 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