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GrumpyOldPizza / arduino-STM32L4

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a small wishlist #2

Open 8bitbunny opened 8 years ago

8bitbunny commented 8 years ago

since i don't know how the HAL works, i thought i'd say my ideas for now.

USB: selectable USB modes (raw hid, flash storage, MIDI instument)

MPU: MPU support

SPI: DMA support 16bit transfers 32bit transfers

Support: a RTOS

More examples: low power modes SPI with DMA example MPU example

GrumpyOldPizza commented 8 years ago

USB: Good thought, but that will take time.

MPU support is not planned. At the end of the day you need a mechanism to statically declare your MPU regions (assigned to IO regions, executables, stack and so on). Doing that dynamically, efficiently and within the resources available is next to impossible. I did implement a uITRON 4.0 RTOS system that could do that, but there are many details that made this unattractive.

SPI: The STM32L4 SPI peripheral has no 32bit wide support, only up to 16bit. DMA is already supported via this API here:

 // STM32L4 EXTENSTION: asynchronous composite transaction
bool transfer(SPISettings settings, const void *txBuffer, void *rxBuffer, size_t count, void(*callback)(void), bool halfDuplex = false);

RTOS: There will be RTOS support real soon (after SDIO for an SDCARD).

rajdarge commented 8 years ago

USB host?

GrumpyOldPizza commented 8 years ago

Sorry, no USB host. There was no space on the PCB to have the necessary additional components. N.b. that there were also no free GPIOs ...

8bitbunny commented 8 years ago

@GrumpyOldPizza so you said spi can transfer 16 bit data natively, how does that work with the dma? (code example?)

GrumpyOldPizza commented 8 years ago

@ramonschepers The Arduino spec only implements 8 bit data. If you are using SPI mode 3, it does not make a difference of you have a 8 bit or a 16 bit data stream (other than byte swapping). For a ILI9341 for example (which wants to have 16 bit color data), that works good enough.

Code example:

SPI.transfer(settings, &tx_data[0], NULL, 256, NULL); while (!SPI.done()) { continue; }

So this send data via SPI, 256 bytes, but does not receive data. The callback is NULL, and it's polling. So really, really bad. Ideally you have a callback that gets called when the transfer is completed. In that callback you can either kick off the next transfer, or update the CS signal.

kriswiner commented 7 years ago

I think it is a good idea to have wish list and I expect users will use this space to ask both dumb and profound questions, both will help us improve the core and the user experience.