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Forum Index : Microcontroller and PC projects : SPI for alternate purpose
| Author | Message | ||||
| PhenixRising Guru  Joined: 07/11/2023 Location: United KingdomPosts: 858 |
Didn't want to pollute the LED matrix thread but it never dawned on me to use the SPI TX for zapping-out a stream of pulses that doesn't tie-up Basic. Any good examples of usage out there? |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6786 |
A PIO is better. They are basically separate processors and run independently of the main CPUs, at their own clock speed. They are also accessible from MMBasic. If you use SPI you are tied to the specialised SPI commands. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4228 |
Hi Phenix, The SPI is not actually running in the background. The SPI WRITE command blocks any other MMBasic execution until the SPI transfer is done. But the command is more efficient than shifting out data in MMBasic. The PIO can work independent of the ARM (and thus MMBasic) but you need to feed it with data to shift out. And that must come from MMbasic. IF however you pack the data in a buffer, PIO can work with that buffer completely independent. So MMBasic only once fills that buffer at each change, and from there MMBasic is free to do whatever it wants. The buffer can be circular, or linear. In case of the matrix sign the SPI sends out data consuming 20% of the MMBasic CPU time. Leaving you with 80% CPU time for the rest of the program. And... you should not use other interrupts, since it will impact the display of text. If you would use the PIO, you would end up with 100% CPU time for MMBasic, and have the ability to run interrupts in you MMBasic code. But it is harder to design, and uses more code. Regards, Volhout Edited 2024-03-18 19:45 by Volhout PicomiteVGA PETSCII ROBOTS |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 858 |
Ah, but more of my focus is on the 100pin ARMmite H7...no PIO  |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6786 |
Dedicate a Pico to the job. Feed the Pico commands via a COM port as that's buffered and it can grab them as needed. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 858 |
Yeah, good point. Was already considering a Pico for a sidekick  |
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