UM1045 datasheet(16/36 Pages) STMICROELECTRONICS

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Block descriptions and configurations

EVALSPEAr320HMI

16/36

Doc ID 18410 Rev 3

4.9

Audio output

Using PWM modulation, the SPEAr320 HMI board, revision 2.0 has mono audio output on

SPEAr320 PWM channel 1. If PL_GPIO37/PWN1 is occupied by an alternate function

(UART0_RTS), PWM channel 2 (PWM2) can be used. To use PWM2, install jumper JP202

(default = uninstalled).

The PWM signal is filtered and amplified by operational amplifier U701; output is available

either though the on-board buzzer (U700), or at the mono 3.5 mm audio jack connector

(CN703). Potentiometer R713 controls the output volume.

If audio output is not used, the amplifier can be bypassed by installing JP702.

See also: Mono 3.5 mm audio jack connector (CN703) on page 23

4.10

LEDs (LD700 through LD703)

There are 4 general purpose LEDs on the top of the board. An LED turns on when its

related GPIO pin is driven high.

4.11

Reset button (B700)

The manual reset button on top of the board resets the microprocessor on the CPU board.

To disconnect the reset button from the CPU board input reset signal, unsolder resistor

R702.

4.12

Setting ADC conversion limits

●

Lower limit: pin CN700-19, jumper JP700

●

Upper limit: CN700-1, jumper JP701

See also: General purpose ADC connector CN700 on page 21

Table 10.

General purpose LEDs

GPIO pin

LED

GPIO pin

LED

PL_GPIO47

LD700

PL_GPIO49

LD702

PL_GPIO48

LD701

PL_GPIO50

LD703

Jumper

Description

Configuration

JP701

Connects the expansion board +2V5_ADC ADC supply voltage to the CPU board pin

ADC_VREFP (Default)

Connects the external ADC expansion supply voltage to the CPU board pin

ADC_VREFP

JP700

Connects the expansion board ADC supply voltage domain GND to the CPU board pin

ADC_VREFN (Default)

Connects the external ADC expansion GND (lower limit) supply voltage to the CPU board

pin ADC_VREFN

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