UM11080
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© NXP B.V. 2017. All rights reserved.
User Manual
Rev. 1.0 — 27 November 2017
10 of 12
NXP Semiconductors
LPC845 Capacitive Touch Kit
User Manual
7.2 Wake button
The Wake button (S2) is for general purpose use by LPC845 applications. It is connected
via a 100 ohm resistor to a 100K ohm pull-up to 3.3V, and to the LPC845 PIO0_4 pin. This
pin can wake the LPC845 from deep power-down.
7.3 User LEDs
Three users LEDs are provided on the board, one blue, one green and one red. The
anodes of the LEDs are connected together, then through solder jumper SJ1 to the 3.3V
regulator output. SJ1 can be opened to prevent leakage from the LPC845 pins through
the diodes if accurate power measurement measurements are being performed. The
LEDs are connected to the LPC845 as shown in the table below.
7.4 Speaker driver
The LPC845 DACOUT output PIO0_29 is route to an IS31AP4991 speaker driver (see
Integrated Silicon Solutions web site for datasheet). This device can drive 8 to 32 ohm
speakers; a 32 ohm speaker is supplied with the board and resistors have been selected
to provide a reasonable volume level for musical tones. If desired, a capacitor can be
added in parallel with the speaker driver feedback resistor, in order to reduce the speaker
circuit bandwidth and reject DAC output sampling artifacts. This capacitor can be added
using the through holes with circuit reference designator C24.
Table 2.
LED connections
LED
LPC845 pin
Notes
Blue (D2)
PIO1_15
Shared with LPCXpresso connector pin 44
Red (D3)
PIO0_12
Shared with ISP pin and LPCXpresso connector pin 45
Green (D1)
PIO0_0
