I want to build my DYO usb keyboard, that including 64bits RISC-V assembly coding of the keyboard firmware.
I have been lurking on the Ox64 for while but I need a few more green lights:
- Is the boot rom enough to fully init the SOC? Aka, I don't need to run extra code I would need to include in my keyboard firmware on the sdcard.
- The hardware programming manual misses the USB2 controller with its DMA programming. Even with some SDK example, you would need the hardware programming manual to understand properly how all that works.
- I want to run my keyboard firmware directly from the sdcard slot, and that directly on the 64bits risc-v core, possible? (no 32bits risc-v core).
The SDCard is not listed as a supported boot target, though you could almost certainly build a small bootloader that's stored in the qSPI flash and then load the rest of your code into RAM from there.
I'm not the most familiar with it, but I believe all hardware init (setting clock source, initialing USB, GPIO, etc.) is handled by the flashable firmware of which there are open source SDKs for.
Then, it means I would need to flash my keyboard firmware, or a SDcard loader firmware.
I guess this is a "standard" flashing protocol over usb, enabled by the right button pressed at power on (plugging the USB cable). Would I need to including the flashing support code into my keyboard/SDcard loader firmware or is it handled separately by a different piece of hardware?
Any specs on the format of the firmware image, to know which core will run the real boot code?
I'm not sure you could flash over USB either without significant work. There's no UART <-> USB device on the Ox64, so you need to use an external one connected to some GPIO pins. You could maybe build a DFU mode yourself, but I'm somewhat skeptical it would work (though it might be possible, there's 3 cores in the thing). Despite there being not one, but TWO USB ports on the Ox64, neither are used for flashing. The micro USB type B connector is only used for power delivery and the USB-c is primarily intended for being a host device, ie. for plugging in a camera module.
Edit: to clarify, there's a bug in the bootrom that prevents the initialization of the USB device. Newer revisions of the Ox64 may fix this.
You can flash it, but you need to use GPIO pins and UART to do so.
The bootrom bug only prevents you from flashing via the on-board USB-c port. You can use a separate USB <-> UART device plugged into GPIO pins to boot/flash.
I don't think that's entirely true, but the 'p' is pSRAM does stand for 'pseudo' and does have refresh circuitry and is slower than true SRAM. By how much, I have no idea.
I have been lurking on the Ox64 for while but I need a few more green lights:
- Is the boot rom enough to fully init the SOC? Aka, I don't need to run extra code I would need to include in my keyboard firmware on the sdcard.
- The hardware programming manual misses the USB2 controller with its DMA programming. Even with some SDK example, you would need the hardware programming manual to understand properly how all that works.
- I want to run my keyboard firmware directly from the sdcard slot, and that directly on the 64bits risc-v core, possible? (no 32bits risc-v core).