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nRF51822 vs nRF8001 when having an external MCU

davman

Hi,

Been using nRF51822 before but on this new design I have an external MCU running the main duties. I've been reading up a bit on both but would like to get some thoughts on pros/cons & comparisons between the two options nRF51822 vs. nRF8001.

Thoughts & Questions:

  • How does the stacks compare between the two? I'm thinking recent SoftDevice releases (6.0) vs what I assume is ROM on the nRF8001?

  • Am I right that the flexibility of doing custom things like future central-role will only be possible with the 51822.

  • To avoid having to maintain and flash two code-bases, are there ways (examples) on how to flash the SoftDevice externally? I could maybe implement SWDIO/SWDCLK via the M3, or have a basic boot-loader on the 51822 that fetches this from the main cpu upon boot.

  • Power consumption, both the nRF and my external M3 will have similar sleep current, that said, both in combo will be more than I want.

  • I assume 51822 and 8001 compares 1:1 from a RF-only perspective?
  • What would be the most efficient way to wake/sleep the nRF during BLE-radio operations only?
  • There will be many crystals, both in cost and board-size. If going for 51822, main xtal could possibly be shared.
    • Is the 32.768 needed with nRF8001 to work-around the periodic RC oscillator recalibration?

Please feel free do add tips and comments.

David

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    Hi David,

    I had faced the same dilemma before when I was using an external microcontroller and TI's CC2541 which has some processing power besides its wireless capabilities.

    What I disliked the most about the aforementioned setup was that I needed to flash twice with two different programmers, one for my microcontroller and one for the Bluetooth chip, which also diminishes your PCB real estate because you need headers and traces for both.

    Of course if you use an SoC that takes care of both your processing and communications, you save a lot of space. However in terms of design flexibility, I always prefer to keep my modules separate. That's why now I use a low-powered microcontroller with nRF8001, which can be programmed over SPI. Unfortunately, I need 3 oscillators in this setup.

    Some microcontrollers such as "EFM32" and "PIC24F GC Series" are more advanced than SoC modules and have some great power-saving features.

    Cheers, Soren

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  • 0

    Hi David,

    I had faced the same dilemma before when I was using an external microcontroller and TI's CC2541 which has some processing power besides its wireless capabilities.

    What I disliked the most about the aforementioned setup was that I needed to flash twice with two different programmers, one for my microcontroller and one for the Bluetooth chip, which also diminishes your PCB real estate because you need headers and traces for both.

    Of course if you use an SoC that takes care of both your processing and communications, you save a lot of space. However in terms of design flexibility, I always prefer to keep my modules separate. That's why now I use a low-powered microcontroller with nRF8001, which can be programmed over SPI. Unfortunately, I need 3 oscillators in this setup.

    Some microcontrollers such as "EFM32" and "PIC24F GC Series" are more advanced than SoC modules and have some great power-saving features.

    Cheers, Soren

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