AN726

Rev. 0.1

7

4.5. Capacitive Sensing Buttons and Slider (CS1)

Four capacitive sensing buttons and one slider comprised of six segments are included on the board to provide the

user interface. Six GPIO pins are connected to the slider as shown in Table 3. The GPIO pins are connected to the

slider in descending order from the location labeled MODE to the location labeled PLAY on the board.

The test points above the slider facilitate adding grounded or shrouded connectors to measure the capacitive

sensing pins.

4.6. Analog Audio Inputs (J1 and MK1)

The stereo jack on the board (J1) allows the board to measure stereo inputs from an input source. The microphone

(MK1) enables the device to measure voice data directly. These signals are conditioned by a bias and gain circuit

provided by a quad op-amp IC (U1), resistors, and capacitors to a range appropriate for the SiM3U164 SARADC

modules.

Table 3. Capacitive Sensing GPIO Connections

Location

Pin

MODE

PB1.1

—

PB1.0

ERASE

PB0.15

—

PB0.14

REC

PB0.13

PLAY

PB0.12