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nrf52 PPI+EasyDMA using timer and SPI

Vishnu Pradeep

Hi,

I am using nrf52832 for my application. The application share same SPI module for two sensors(with sensors are selected using two chip select pins). Is it possible to implement PPI channel between a timer and this SPI module so that I can collect data from both the sensors every 1ms? I would like to collect the SPI data using EasyDMA and send these data through BLE every 50ms. how can it be achieved with the help of PPI and EasyDMA?

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  • 0

    Yes, it is possible. may be something like:

    1. Setup spi, transmission buffers, timers etc
    2. Start 1st SPI transmission (either by timer PPI or manually by software - every 1ms)
    3. When transmission end, toggle CS pins by gpiote (triggered by spi end ppi), start timer
    4. when timer end, start second spi transmission (buffer pointer automatically incremented by array list).
    5. Data may be moved somewhere else, or just long arraylist may be used.
    6. goto 2?

    I may have skipped something, but in general, that should be doable. It also can be achieved quite easily completely without using ppi, timers etc - just by software app_timer, as 1ms is not that high freq.

    About sending it by BLE every 50ms... I would just use app_timer too for that.

  • 0 in reply to Wojtek

    Thank you for shedding some light. My concern was with the toggling of CS pin. I have to do an SPI transfer by manually making one of the CS pin low. Then initialise GPIOTE toggle for two CS pins, initialise timer PPI for SPI transfer (1ms). Timer EEP ->SPI TEP,SPI EEP -> GPIOTE TEP. Can I use a software interrupt flag to store sensor readings into respective arrays ?

    Yeah. It can be done simply by software app timer and I did that. But I need to reduce CPU intervention as little as possible. That is why I am planning to use both PPI and EasyDMA advantages. I am using both the features for the first time. Can you please help me with EasyDMA also? Like how can I configure EasyDMA for this application and what are the things to be considered while using EasyDMA? Is there an example code for PPI+EasyDMA available??

    Thanks & regards, Vishnu

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  • 0 in reply to Wojtek

    Thank you for shedding some light. My concern was with the toggling of CS pin. I have to do an SPI transfer by manually making one of the CS pin low. Then initialise GPIOTE toggle for two CS pins, initialise timer PPI for SPI transfer (1ms). Timer EEP ->SPI TEP,SPI EEP -> GPIOTE TEP. Can I use a software interrupt flag to store sensor readings into respective arrays ?

    Yeah. It can be done simply by software app timer and I did that. But I need to reduce CPU intervention as little as possible. That is why I am planning to use both PPI and EasyDMA advantages. I am using both the features for the first time. Can you please help me with EasyDMA also? Like how can I configure EasyDMA for this application and what are the things to be considered while using EasyDMA? Is there an example code for PPI+EasyDMA available??

    Thanks & regards, Vishnu

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