ADXL355 external sync

Hello,

I have same questions about EXT_SYNC=01 Mode of ADXL355.

Could you please advise me  timing specification about the external sync signal? Are there any constraint about the sync signal?

According to the datasheet of ADXL355, EXT_SYNC=01 mode can be used with only a single sync pulse. Can we send only one

sync pulse for synchronization in this case? Or should we send sync pulse continuously?

Best regards,

Akira

Parents
  • Hi,

    I guess if we have to send multiple sync pulses, we need to align them with the decimation filters which is a tedious task. Hence they recommend to use a single pulse but this will definitely lead to drifting of clocks after a certain time. 

    Also when you enabled EXT_SYNC=01 mode, did you also assign EXT_CLK = 1 and set the DRDY_OFF bit of the Power Control Register? Is the EXT_CLK always 1.024MHz irrespective of the required Output Data Rate?

    Swarna

Reply
  • Hi,

    I guess if we have to send multiple sync pulses, we need to align them with the decimation filters which is a tedious task. Hence they recommend to use a single pulse but this will definitely lead to drifting of clocks after a certain time. 

    Also when you enabled EXT_SYNC=01 mode, did you also assign EXT_CLK = 1 and set the DRDY_OFF bit of the Power Control Register? Is the EXT_CLK always 1.024MHz irrespective of the required Output Data Rate?

    Swarna

Children
  • Hence they recommend to use a single pulse but this will definitely lead to drifting of clocks after a certain time. 

    My interest is to use one high stable EXTERNAL CLK source for a number of ADXL355, no internal CLK at all. So, I don't expect any drift and additionaly use the EXTERNAL CLK as real time clock.

    In the Datasheet for ADXL354/355 the table 46 on the page 38 the next comment is placed for EXT_SYNC=01 mode:

    "External sync, no interpolation filter. After synchronization, and for EXT_SYNC within specification, DATA_RDY occurs on EXT_SYNC."

    Is it mean, that after one sync pulse one may get Data_Rdy pulses?