RM0312 datasheet(257/275 Pages) STMICROELECTRONICS

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RM0312

ProxSense™ (PXS)

273

Other parameters to reduce consumption

The principle factor of power consumption in the ProxSense module is the conversion time.

For optimal power consumption, it is necessary to select the lowest acquisition length that

will not adversely affect sensitivity.

To further reduce power consumption, it is recommended to ground the Rx pins when they

are disabled by resetting the PXS_RXINSR register and to configure the GPIO pins

connected to Tx channels as output low level when they are not driven by the ProxSense.

If the Rx lines do not interact with each other, disabling Rx coupling by resetting the

RXCOUPLING bit in PXS_CR2, will also reduce power consumption as the Rx line drive is

stopped as soon as the corresponding CS reaches the threshold voltage (VTHR).

The sample and hold strength is confgured using the BIAS[1:0] bits in PXS_CR3 to set the

minimum value that will allow the final discharged voltage to be maintained while the

transmit lines (Tx) are transitioning back to low.

22.8

PXS interrupts

The ProxSense has two interrupt request sources:

•

End of conversion (EOC) interrupt, which is activated when all of the enabled channels

have completed their acquisitions.

•

First channel conversion completion (FCC) interrupt, which is activated as soon as one

channel completes its acquisition.

To enable interrupt requests for each interrupt source, set the required EOCITEN or

FCCITEN interrupt enable bit in PXS_CR2.

Before enabling an interrupt, it is recommended to clear the EOCF and FCCF status flags in

PXS_ISR to avoid triggering an interrupt due to a previously completed acquisition.

Before exiting the interrupt routine, the EOCF and FCCF status flags must be cleared by

writing ‘0’ in the corresponding bit in PXS_ISR.

Note:

These interrupts enable the device to exit from Wait and Active-halt modes but, not from

Halt mode.

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