>How do I trigger the SPI read every ~1ms?
You could use a timer , but if just 1ms is ok: use the systick int , write there just the HAL command to start the gpdma transfer...thats it.
> Is it possible to interrupt the CPU only if the 3 bytes read from the SPI differ from the previous value?
No, somebody has to compare the old--new values and decide then; this is a simple job for the cpu.
So just use the dma finished int , compare there the 3 bytes and decide "set new value "or not.
Maybe needs some 16 cpu clocks or so, thats so fast, you will not notice it ...
and dont forget to set optimizer , -O2 (i use always), to get the best speed of an arm cpu.
And you can ask the sidekick Ai here, how to do in detail: klick on
and ask:
how to start gpdma transfer in systick int ?
1. Starting GPDMA Transfer in SysTick Interrupt
To start a GPDMA transfer in a SysTick interrupt, you need to ensure the DMA channel is properly configured before enabling the transfer. The general approach is:
- Program the DMA address in the relevant register before enabling the channel.
- This setup allows the DMA controller to fetch or update data buffers for the transfer when triggered, such as from an interrupt handler like SysTick.
2. Triggering GPDMA Transfer from an Interrupt Handler
The procedure to trigger a DMA transfer from an interrupt handler (such as SysTick) involves:
- Initializing and enabling the relevant DMA channel as per the initialization procedure.
- When the interrupt occurs (e.g., SysTick_Handler), reinitialize or start the DMA channel for the next transfer.
- For each transfer, ensure the DMA channel is correctly set up and enabled within the interrupt handler.
- After the transfer completes, handle the completion interrupt and repeat the process for subsequent transfers if needed.
3. Configuring and Starting GPDMA Transfer
To configure and start a GPDMA transfer in STM32:
- In STM32CubeMX, select GPDMA1 under System Core and set the mode (Standard Request or Linked-list).
- Assign channels and configure the request (e.g., USART1_RX) in the DMA Settings tab.
- In your code, include the necessary headers, declare buffers, and configure the DMA handle.
- For linked-list mode, link the queue to the channel and register error callbacks.
- Start the DMA transfer using HAL_DMAEx_List_Start_IT (linked-list) or HAL_DMA_Start_IT (standard).
- Monitor transfer completion and handle errors as needed.
- This process can be initiated from within the SysTick interrupt handler by calling the appropriate HAL function to start the transfer.
Summary
To start a GPDMA transfer in a SysTick interrupt:
- Configure the GPDMA channel and request source in CubeMX or manually in code.
- In the SysTick interrupt handler, call the appropriate HAL function to start the DMA transfer.
- Ensure the DMA channel is properly initialized before enabling the transfer in the interrupt context.
For additional support or to discuss your specific application with ST experts, you’re welcome to join conversations in STM32 forums.
