UM11158
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User manual
Rev. 1.6 — 17 March 2022
17 of 24
NXP Semiconductors
UM11158
LPCXpresso55S69/55S28 Development Boards
7.3 Accelerometer
The board includes an NXP MMA8652FCR1 accelerometer, interfaced to Flexcom 4
(ports P1_21 and P1_20) with its interrupt output connected to P1_19 (this signal is also
shared with the Expansion connector P18 via a 100 ohm resistor (R5).) The
accelerometer has an I2C address of 0b0011101.
Note that the accelerometer can only be used when the board is configured for 3.3V
operation. Resistor R20 may be removed to disconnect the MMA8652 from the supply
rail, and P25 may be installed to provide a convenient way to connect/disconnect it to/from
power.
Resistors R3 and R4 are zero ohm links, provided to enable the MMA8652 to be
disconnected from P1_20 and P1_21 to avoid leakage effects when the board is
configured for 1.8V operation.
I2C software drivers are provided as part of the MCUXpresso SDK, and example code is
provided to illustrate how to read values from the accelerometer.
7.4 RGB User LED
An User controlled RGB LED is provided on the Board, located on the right hand edge.
The LEDs in this device are controlled by LPC55Sxx ports P1_4 (Blue), P1_6 (Red), P1_7
(Green) with the LEDs being illuminated when the respective LED is pulled low. Note that
these port lines are also connected to expansion connector P18.
7.5 Buttons
Four buttons are provided on the LPCXpresso55S69, as described in this section.
7.5.1 ISP (S1)
P0_5 is pulled up to VDD via a 2.2 kohm resistor; pressing this button will pull P0_5 low.
This port is read by the LPC55Sxx boot code to determine if the MCU should enter In
System Programming (ISP) mode. The main purpose of this button is to force the
LPC55Sxx into ISP mode at boot time; to do this hold down this button while pressing and
releasing the Reset button, or while connecting power to the board. While the main
purpose of ISP mode is to program the flash of the LPC55Sxx, forcing the MCU into this
mode places it into a known state in which development tools can gain debug control. If an
application in flash is crashing or disabling the SWD port unintentionally, then ISP mode
can be useful to recover control of the board. Refer to the LPC55S6x/S2x/2x User Manual
for more information on ISP mode.
The ISP button can also be used in user application code. Care should be taken if P0_5 is
configured as an output driving high, since pressing this button will short it to ground.
D3
P0_25
IOCON function 2
Card detect
P0_21
IOCON function 2
Power enable
P1_0
GPIO. Active low.
Table 3.
Micro SD card connections
SDIO interface signals
Port
Notes
