Project Peacock
From Hackstrich
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
- SRAM
- Output converter
- TMDS converter for DVI
- DAC for VGA
- Display Controller MCU
- 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
- The Arria II GX and Cyclone IV GX series both have these transceivers
- 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
- This concept also doesn't require a transceiver-equipped FPGA so should in theory be a bit cheaper
- 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
