Block descriptions and configurations
EVALSPEAr320HMI
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
1 2 3
1 2 3
1 2 3
1 2 3
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