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cc2640 examples Cortex M3 load

IainRist
Intellectual 711 points

Other Parts Discussed in Thread: CC2541, CC2640

I am interested in using the cc2640 for a future iteration of a product that currently uses a cc2541 as a network processor and another MCU as the host. I would like to combine the application and stack onto one chip, using the cc2640.

I have not been able to find any numbers, other than the 48 MIPS, for the compute resources of the cc2640. As I understand it, the BLE stack uses some of those MIPS. I want to know how many MIPS the stack uses.

I understand that different applications will use the stack in different ways, affecting the MIPS. Does anyone have numbers for the number of MIPS used by the various example applications, so I can get a feel for the number of MIPS free for use by my application?

  • 0
    TI__Mastermind 34660 points
    Hello. I'm not sure I understand your question. When processing, the stack will use the full processing power of the m3. When your application is processing, it will have full processing power. Are you trying to find out how often the application can process? This is dependent on BLE activity as the stack needs to process for each connection / advertising event.
  • 0 in reply to Tim C
    Intellectual 711 points

    Tim, your understanding of my question is correct. I am after average loads.

    I understand the M3 load due to the stack will be highly dependent on application and the related BLE usage.

    I am after average load figures for the stack component of the example projects so I can get a feel for the stack contribution to overall load.

  • 0 in reply to IainRist
    TI__Mastermind 34660 points
    I think your best bet is to use the spreadsheet included in the power measurement app note to get an idea of how often the stack will process for a given case:
    www.ti.com/.../swra478.pdf
  • 0 in reply to Tim C
    Intellectual 380 points
    Hi everyone

    This topic is also pretty interesting for me, not in terms of low power but in terms of saving an additional MCU: the CC2640 has an integrated Cortex M3 as well was an M0 which is used "to run the BLE Radio Firmware".
    The question is: how much is the M3 involved in the BLE Stack and how much is the M0 involved? Is the M0 really just used for the 3 lower levels of the Stack (e.g. up to HCI) or is there more? Where exactly is the "cut" between the M0 and the M3 regarding the BT Stack? If its at the HCI level, the M3 will have a much bigger load to handle as when the cut is at the GATT level regarding the Stack.

    Thank you very much in advance
    Regards,
    Matthias
  • 0 in reply to Matthias Mueller
    TI__Mastermind 29650 points
    Matthias,

    An answer to your question is found here:
    e2e.ti.com/.../1659394

    Looking at the power plots as mentioned might fool you as the Cortex M3 is available for much of this time. The BLE stack's percentage of the load will also vary greatly with desired connection intervals etc.

    That said, most BLE products are designed to stay in low power modes for most of their time, waking up only when needed.
    Say you are using e.g. 100ms connection interval you will have over 99% available run time left on the Cortex M3 for the application.

    Regards,
    Svend