Hardware Description
9
SLLU250 – November 2016
Copyright © 2016, Texas Instruments Incorporated
BOOSTXL-RS232 BoosterPack™ Hardware
Figure 8. Header J9
3.5.3
Utilizing INVALID Signal
The J9 3 × 2 header also allows for the option to monitor the INVALID pin of the TRS3122E by linking it to
a GPIO pin on a LaunchPad. By placing a jumper across pins 5 and 6 on J9, see
, the INVALID
pin will be connected to GP14. The GPIO port on a LaunchPad can then be set to an input and used to
monitor the INVALID pin. See
to learn more about the INVALID pin.
NOTE:
If the INVALID pin is not intended to be monitored, remove the jumper.
3.5.4
Assigning Desired Supply Voltage
The BOOSTXL-RS232 BoosterPack is populated with a linear regulator to drop the typical 3.3-V V
CC
on
most LaunchPads to 1.8 V. This allows for communication with LaunchPads that are capable of
communicating at 1.8-V logic levels. To switch between a 1.8-V and 3.3-V supply, use a jumper on J12 to
short the center V
CC
pin to the desired supply voltage, see
. A short between pin 1 and 2 results in
3.3-V V
CC
and a short between 2 and 3 results in 1.8-V V
CC
. Pin 1 on J12 is denoted with a white line
along one edge of the pin, as seen in
. While V
L
and V
CC
are independent on the TRS3122E
device itself, these two pins are tied together on the BoosterPack. This way V
L
cannot accidentally be set
higher than V
CC
. This option was added to display the ultra-low voltage capabilities of the TRS3122E.
NOTE:
V
CC
and V
L
should only be set to 1.8 V if the BOOSTXL-RS232 is intended to interface with a
LaunchPad that operates at 1.8-V logic levels. Otherwise TI recommends leaving the jumper
across pins 1 and 2 of J12.
Figure 9. Supply Select
