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maximum baudrate nrf52 slower than BLE 5.0

Hi, we're starting to plan an update to BLE 5.0 (specifically the double bandwidth feature) on a product using the nRF521832 connected to an STM32. We were just testing increasing our internal communication speed, and realised the nRF52 is limiting us to "Up to 1 Mbps baudrate"

That's slower than the net OTA bandwidth of ~1.4Mbps!

Any chance we could double that? My suggestions would be:

  1. using 8x oversampling rather than 16x?
  2. utilising a faster clock (PCLK32M) when available?

Thanks!

PS: we'll be outputting the nordics clock on a GPIO to drive the clock input on the STM32, so clock drift between the two devices should not be an issue for us ;-)

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  • Hi

    I can't think of any easy and reliable way to achieve serial communication higher than 1MBaud if you only have 2 GPIO's available.

    With 3 GPIO's you could do uni-directional SPI up to 4MHz at least (bi-directional if you have 4 GPIO's).

    Do you really need to transfer data continuously at a rate higher than 1Mbps?
    Keep in mind that 1.4Mbps is the absolute maximum bandwidth, and in practical use the actual bandwidth is likely to be lower than this. By optimizing the application for a lower bandwidth you will have some bandwidth left over for retransmission, making the link more reliable and the data rate more consistent.

    Best regards
    Torbjørn Øvrebekk

  • Hi, thanks for the reply.

    I did offer two suggestions for easy and reliable ways of doubling the maximum serial communication speed...

    well, why offer double bandwidth, if you suggest not to use it? ;-)

    Yes, we will need to use the maximum possible bandwidth continuously, such as transmitting a live video feed, as in this demo: devzone.nordicsemi.com/.../ only that the camera is attached to the STM. Of course, in less than ideal cases, we won't reach the maximum, but while we can, we'd like to make use of it!

    As I wrote in earlier comments, our PCBs are done and we only have UART and I2C connected between the two chips, so no chance to switch to SPI... and even if it were, that's not the question here ;-)

    We'll survive with 1M, but would still like to know if we can achieve 2M (or at least 1.4M)

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  • Hi, thanks for the reply.

    I did offer two suggestions for easy and reliable ways of doubling the maximum serial communication speed...

    well, why offer double bandwidth, if you suggest not to use it? ;-)

    Yes, we will need to use the maximum possible bandwidth continuously, such as transmitting a live video feed, as in this demo: devzone.nordicsemi.com/.../ only that the camera is attached to the STM. Of course, in less than ideal cases, we won't reach the maximum, but while we can, we'd like to make use of it!

    As I wrote in earlier comments, our PCBs are done and we only have UART and I2C connected between the two chips, so no chance to switch to SPI... and even if it were, that's not the question here ;-)

    We'll survive with 1M, but would still like to know if we can achieve 2M (or at least 1.4M)

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