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QUAD SPI External Memory Performance nRF52840

Hi There - I'm very new to electronic design and need help making a key design decision. Specifically I want to know that the performance will not be a problem when writing to external memory from a nRF52840 over Quad Spi. I don't want to end up making a school boy error whereby the memory bus or memory chip cannot accomodate the rate at which I want to write data - or maybe there is another practical reason I am unaware of.

Quite simply I want to poll a magnetic position encoder and an accellerometer at circa 200Hz over the regular spi bus and then write their values to the flash memory on the Quad spi bus for analysis later. This is essentially the data logger part of the application. Probably worth mentioning that we are doing some other data analysis on the data as the sensors are polled so some overhead there for the M4 processor - but an existing application uses an M0 processor at 16Mhz and does this analysis fine so we reckon that the M4 at 64Mhz should easily cope.

Really before proceeding I am looking for an indication that I am going to be able to write a timestamp and two sensor values to the external memory at 200Hz - possibly even higher - and it will just work as expected. 

Feedback gratefully received,

Alan

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  • Hi,

    I do not see any reason why this shouldn't work. You will have 5ms here between each new polling, this is plenty of time. I guess you could even buffer up some data before writing to QSPI also if you wanted.

    Best regards,
    Kenneth

  • Hi Kenneth - please keep me right here - if I understand correctly you are saying that 5ms is enough time for the flash memory to complete its write of the data?
    - Can I also ask you, is this the fastest way for a nRF52840 to write to external memory? If not what would be the fastest? And correct me if I am wrong - there doesn't seem to be any sdio and thus eMMC support on these mcu's? Another question - I assume eMMC over sdio would be faster if it was available but an not sure if I am correct - can you tell me? 

    Thanks in advance
    Alan

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  • Hi Kenneth - please keep me right here - if I understand correctly you are saying that 5ms is enough time for the flash memory to complete its write of the data?
    - Can I also ask you, is this the fastest way for a nRF52840 to write to external memory? If not what would be the fastest? And correct me if I am wrong - there doesn't seem to be any sdio and thus eMMC support on these mcu's? Another question - I assume eMMC over sdio would be faster if it was available but an not sure if I am correct - can you tell me? 

    Thanks in advance
    Alan

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