Cirrus-logic AN74 Manual do Utilizador descarregar pdf (Página 9)

AN74

AN74Rev2 9

/**************************************************************************************

* Routine - read_register

* Input - command

* Output - low_byte, mid_byte, high_byte

* This subroutine reads an internal register of the ADC

/**************************************************************************************/

void read_register(char command){

if(mode == 1) P1 = 0xF4; /*Assert CS

if necessary */

transfer_byte(command); /*Transfer Command Byte to CS5525/6/9*/

high_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/

mid_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/

low_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/

if(mode == 1)P1 = 0xF5; /*Deassert CS

if necessary */

}

/**************************************************************************************/

* Routine - acquire_conversion

* Input - command

* Output - Conversion results in memory locations HIGHBYTE, MIDBYTE and

* LOWBYTE. This algorithm performs only single conversions. If

* continuous conversions are needed the routine needs to be

* modified. Port flag is zero.

* HIGHBYTE MIDBYTE LOWBYTE

* 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0

* 16-bit results MSB LSB 1 1 1 1 0 0 OD OF

* 20-bit results MSB LSB 0 0 OD OF

* This subroutine initiates a single conversion.

/**************************************************************************************/

void acquire_conversion(char command){

/*** Read Configuration Register to Prevent Previously Set Bits from being Altered ***/

read_register(0x94); /*Read Configuration Register*/

low_byte = low_byte|0x20; /*Assert Port Flag Bit*/

write_to_register(0x84,low_byte, mid_byte, high_byte);/*Actually Send Commands*/

/*Acquire a Conversion*/

if(mode == 1)P1 = 0xF4; /*Assert CS

if necessary*/

transfer_byte(0xC0); /*Transfer Command to CS5525/6/9*/

toggle_sdo(); /*Clear SDO*/

high_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/

mid_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/

low_byte = receive_byte(); /*Receive Command Byte from CS5525/6/9*/

if(mode == 1) P1 = 0xF5; /*Deassert CS

if necessary*/

}

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Cirrus-logic AN74 Manual do Utilizador Página 9

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