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SPI write feasible before or during a connection event?

Hermann Menning
Expert 1305 points

Other Parts Discussed in Thread: CC2541

I have a cc2541 communicating over SPI wit an accelerometer.

So far I have used HCI_EXT_ConnEventNoticeCmd to read and write over SPI after a connection event to keep current consumption low. When I activate the accelerometer (which takes one SPI write) it takes a few milliseconds to provide reliable data. Best practice to reduce current consumption would be activate the accelerometer right before the connection event or somewhere at the beginning of a connection event so that the acceleromter could settle during the connection event and would be ready to be read afterwards.

Any thought how this could be done?

Best Regards.

  • 0 in reply to Hermann Menning
    Guru 31280 points

    Let's say that X (millisecond) represents the interval between two sequential connection.

    In the end of connection open timer execution with timeout of X-DELTA (milliseconds) which

    sets some event where the Accelerometer is powered up and gets stable. 

  • 0 in reply to Igor Sherer
    Expert 1305 points

    Thank you for your response.

    I had something similar in mind but had some concerns with that approach:

    The code that is executed before the connection event only consumes 800 ticks at 32mhz. I want to conserve as much power as possbile (no cpu idle time till RF event). Thus, timer execution with timeout of X-DELTA has to be very accurate. Although i can get accurate timings for the next RF event with LL_TimeToNextRfEvent I dont think it is accurate enough when using osal_start_timerEx, is it?