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I thought about building toy pc with rp2040 but I wasn’t able to solve gpu problem. Driving display seems very hard task without some dedicated hardware. And us

I thought about building toy pc with rp2040 but I wasn’t able to solve gpu problem. Driving display seems very hard task without some dedicated hardware. And using serial output is not fun.

II2II 5y ago
There are a lot of options on this front. As far as I can tell, most displays for embedded platforms are sold as modules that you interface with via a serial or parallel bus. There are libraries out there to handle the grunt work, if you don't want to dig through data sheets yourself. If you want something that doesn't use any dedicated hardware, interfacing with analog displays (e.g. NTSC/PAL/VGA) can be done with a handful of resistors on GPIO pins. Conceptually, it is easier but actually dealing with timing is a pain. Again, libraries that deal with the grunt work are available.
ChuckMcM 5y ago
So, FWIW, I've been playing around with this. I've got an FPGA board that has an HDMI output[1]. I have a simple 1280 x 720 frame buffer running on it (read the DRAM, display it on the monitor. I'm building a carrier board to connect it to an STM32F429 Nucleo-144 board using the ST Micros flexible memory controller (FMC) peripheral. This will present the frame buffer contents to the STM32 as memory. Additionally, some "control registers" are being implemented in the FPGA that can do certain actions. At a minimum they are "clear to one color", "copy region", "scroll region", and "copy glyph". The STM32 has the DMA2 peripheral that does a lot of cool bitblt type functions but these can be nominally slowed down by not synchronizing with the FPGA's schedule for displaying things. The STM32 is running micropython. The "plan", such as it is, is to let the REPL run using the display as its terminal, and a "graphics mode" to reserve parts of the screen for graphics. The small goal is to re-create sort of the VIC-20/C64/ZX Spectrum kind of "vibe" (interpreted language easy access to the graphics) and then build from there. Clearly the basic frame buffer is like 20% of the FPGA so there is lots of room to do other stuff in there. [1] https://www.kickstarter.com/projects/1812459948/minispartan6-a-powerful-fpga-board-and-easy-to-use https://www.kickstarter.com/projects/1812459948/minispartan6...
- vbezhenar 5y ago
  Thanks, this sounds awesome and interesting topic for learning in the future.
niutech 5y ago
You can use ESP32 for a toy PC, check out FabGL.

I thought about building toy pc with rp2040 but I wasn’t able to solve gpu problem. Driving display seems very hard task without some dedicated hardware. And using serial output is not fun.

II2II 5y ago

There are a lot of options on this front. As far as I can tell, most displays for embedded platforms are sold as modules that you interface with via a serial or parallel bus. There are libraries out there to handle the grunt work, if you don't want to dig through data sheets yourself. If you want something that doesn't use any dedicated hardware, interfacing with analog displays (e.g. NTSC/PAL/VGA) can be done with a handful of resistors on GPIO pins. Conceptually, it is easier but actually dealing with timing is a pain. Again, libraries that deal with the grunt work are available.

ChuckMcM 5y ago

So, FWIW, I've been playing around with this. I've got an FPGA board that has an HDMI output[1]. I have a simple 1280 x 720 frame buffer running on it (read the DRAM, display it on the monitor. I'm building a carrier board to connect it to an STM32F429 Nucleo-144 board using the ST Micros flexible memory controller (FMC) peripheral. This will present the frame buffer contents to the STM32 as memory. Additionally, some "control registers" are being implemented in the FPGA that can do certain actions. At a minimum they are "clear to one color", "copy region", "scroll region", and "copy glyph". The STM32 has the DMA2 peripheral that does a lot of cool bitblt type functions but these can be nominally slowed down by not synchronizing with the FPGA's schedule for displaying things. The STM32 is running micropython. The "plan", such as it is, is to let the REPL run using the display as its terminal, and a "graphics mode" to reserve parts of the screen for graphics. The small goal is to re-create sort of the VIC-20/C64/ZX Spectrum kind of "vibe" (interpreted language easy access to the graphics) and then build from there. Clearly the basic frame buffer is like 20% of the FPGA so there is lots of room to do other stuff in there. [1] https://www.kickstarter.com/projects/1812459948/minispartan6-a-powerful-fpga-board-and-easy-to-use https://www.kickstarter.com/projects/1812459948/minispartan6...

vbezhenar 5y ago
Thanks, this sounds awesome and interesting topic for learning in the future.

niutech 5y ago

You can use ESP32 for a toy PC, check out FabGL.