WEBENCH® Tools/MSP430FR2533: MSP430FR2533

Hello Hassan,

You can leave unused CapTIvate sensing pins unconnected without adverse effects in many cases, but floating pins can act as noise sources, so it is a good idea to terminate them in some way as you mention.

Let's distinguish pins in two ways:

1. CapTIvate pins shared with GPIO's, such as CAP1.0

2. CapTIvate pins not shared with GPIO's (dedicated pins), such as CAP2.0

Case 1 - Shared IO's

CapTIvate pins that are shared with GPIO's can easily be set to output low internally using the GPIO function, and you can leave the external pin as a no connect.  You can also tie the unused pins low using a pulldown resistor internally if desired.  In the CapTIvate starter projects, pin muxing is done in the CAPT_BSP.c file.  If you open this file (contained in the captivate_app directory) you can adjust the pin muxing settings as you desire.

Case 2 - Dedicated IO's

CapTIvate pins that are not shared with GPIO's (the dedicated pins that only list CAPx.y as the pin function) can not be grounded with a GPIO mechanism as there is no GPIO circuit connected to the pin.  Thus, you would terminate these pins either externally as you mention, or internally using some CapTIvate Software Library set-up functions to tie them low.  This would be the method I recommend, as you don't risk shorting anything out should you incorrectly configure something by accident.  The method for this is as follows:

For each unused dedicated CAP IO, you can make these additional calls after you call CAPT_appStart() to switch the IO to output low:

MAP_CAPT_setChannelEnable(2, 0); // Enable the pin
MAP_CAPT_clearChannelActive(2, 0); // Clear active status (not used for a conversion)
MAP_CAPT_setChannelOffState(2, 0); // Set pin to ground rather than Hi-Z state

Let me know if you have any questions!

Regards,
Walter