Cirrus-logic AN131 Manual do Utilizador descarregar pdf (Página 7)

AN131

AN131REV2 7

MAIN EQU * ;Start from reset vector

;*** Initialize and Calibrate the system ***

JSR initialize ;Initialize the System

JSR write_csrs ;Modify the Channel Setup Registers

JSR calibrate ;Calibrate ADC Offset

JSR rwgain ;Write and read gain register

;*** Continuously perform single conversions ***

mloop: JSR convert ;Obtain a conversion from the ADC

JMP mloop ;Keep Looping

;*** End MAIN ***

;*****************************************************************************

;* Subroutines

;*****************************************************************************

;* Routine - initialize

;* Input - none

;* Output - none

;* This subroutine initializes Port D as a SPI port to interface to the

;* CS5521/22/23/24/28 ADC.

;* A time delay for the ADC oscillator start-up period is provided, as well

;* as a delay for the ADC’s power-on reset.

;* Typically, a 32.768 KHz crystal has a start-up time of about 500ms. After

;* this delay, an additional 1003 XIN cycles are delayed for the ADC reset.

;* The ADC’s serial port is also reset at this time

;*****************************************************************************

initialize LDA #%01010000 ;Load ACCA with values for SPCR

STA SPCR ;Setup SPI Port

LDA #$40 ;Load ACCA with delay count value

JSR delay ;Delay 1003 XIN for power-on reset

LDA #220 ;Load ACCA with delay count value

JSR delay ;Delay for oscillator start-up 170ms

;*** Initialize ADC serial port ***

LDX #$0F ;Value of 15 for first 15 Bytes

LDA #$FF ;Load ACCA with all 1’s

sloop: JSR send_spi ;Send info to ADC

DECX ;Decrement Counter

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Cirrus-logic AN131 Manual do Utilizador Página 7