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

[David Edwin]

Sleep current for the nRF8001 is slightly lower than the nRF51. See section 12.4 Current Consumption parameters in I_idle and I_sleep in the nRF8001 datasheet I_idle is lower for the nRF8001 while i_sleep is almost the same between nRF51 and nRF8001

You can also implement an complete power cutoff for the nRF8001 and nRF51, by which the power is cutoff (you should first read the RAM by do a Read Dynamic data) and when the nRF8001 is required again, the power can be restored and the RAM is also restored using Write Dynamic Data

This enables you go to the lowest power states possible. The nRF8001 enables this out of the box using Read Dynamic Data and Write Dynamic Data.

You should examine if the nRF8001 fits your needs and then consider the nRF51 if it does not, especially if you are using it as a connectivity device as the nRF8001 interfaces are easier to use and to get started.