MCU selection

[drewsum]

• PIC32MZ EF:
  • Pros:
  • Drew extremely familiar with this
  • Lots of code overlap with existing projects
  • Lots of pin count and memory options
  • KiCad symbols ready to go
  • Hand solderable packages
  • The compiler and IDE are awesome, no need to bit shift to control registers
  • Easy debug
  • Extremely flexible interrupts
  • Cons:
  • Memory for graphics is limited
  • No built in LCD controller (would need to leverage other peripherals not meant for this)
  • Unsure how USB would work (I just normally use a UART to USB bridge)
  • No built in SD card controller
  • MPLAB Harmony code framework is garbage (could generate peripheral drivers and copy to bare metal project)
• PIC32MZ DA:
  • Pros:
  • Meant for graphics applications
  • More internal SRAM available than 32MZ EF
  • Built in LCD controller
  • Built in on-die 32MB DDR2
  • Certain options support 128MB external DDR2
  • Very similar to PIC32MZ EF
  • Built in SD card controller
  • The compiler and IDE are awesome, no need to bit shift to control registers
  • Apparently there is a GUI for configuring the graphics capabilities
  • Available in hand solderable packages, also BGA
  • Dedicated GPU
  • Easy debug
  • Extremely flexible interrupts
  • Its cool af
  • Cons:
  • New part to both of us
  • Some code overlap with 32MZ EF, might be able to branch off easily though, but this would require lots of new code
  • Would need new KiCad symbols
  • Would need lots of support circuit design thought/analysis/critical thinking, not just copy and paste
  • Unsure how useful the graphics configuration applications actually are, they could be hot steaming garbage and we'd be on our own
• STM32:
  • Pros:
  • It's a thing that exists and apparently the support is good
  • I have seen that they have some kind of graphics support
  • Cons:
  • I have no idea how to use these
• ESP32 S3:

[drewsum]

I had chatted with Michael a bunch about this, and the PIC32MZ DA seems like a good fit. This will require a lot of investment in code and hardware development, but since it's meant for video, it seems like a good idea.

There are a few different flavors of PIC32MZ DA, but the more modern SKUs from circa 2019 have a datasheet here: https://ww1.microchip.com/downloads/aemDocuments/documents/MCU32/ProductDocuments/DataSheets/PIC32MZ-Graphics-%28DAK-DAL-DAR-DAS%29-Family-Datasheet-DS60001565D.pdf

They offer them in BGA and LQFP packages in high pin counts. I looked into the BGA package in KiCad briefly and it looks like the ball pitch is barely too tight to make work with JLCPCB design rules. I think it would be easier to use the LQFP package, but would take up much more space.

Looking at the SKUs for this package, these are available:

I think the PIC32MZ2064DAR176 is most realistic. The high internal SRAM is nice, as is the internal 32MB DDR2, which we'd use as a frame buffer for the LCD. We could also try to get fancy with microchip's GUI generation tools.

This is enough of a departure from my current projects to make this interesting and require engineering and firmware rigor, but is close enough where a lot of code could be ported over easily.

PIC32MZ2064DAR176 appears to be available in ok-ish quantities according to octopart. If we design a PCB around this, the good news is that there are other options that are drop in replacements, just with different memory sizes. So I think that the part selection is actually quite flexible.