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set/clear port bits with atomic instructions instead of read-modify-write, saves time+space, allows port usage in ISR

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@4022 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jörg Hohensohn 2003-11-06 01:34:50 +00:00
parent 9e95757928
commit 75bab49a54
8 changed files with 88 additions and 67 deletions
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35
firmware/drivers/i2c.c
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@ -21,22 +21,23 @@
#include "kernel.h"
#include "thread.h"
#include "debug.h"
#include "system.h"
#define PB13 0x2000
#define PB7 0x0080
#define PB5 0x0020
/* cute little functions */
#define SDA_LO (PBDR &= ~PB7)
#define SDA_HI (PBDR |= PB7)
#define SDA_INPUT (PBIOR &= ~PB7)
#define SDA_OUTPUT (PBIOR |= PB7)
/* cute little functions, atomic read-modify-write */
#define SDA_LO __clear_bit_constant(7, &PBDRL)
#define SDA_HI __set_bit_constant(7, &PBDRL)
#define SDA_INPUT __clear_bit_constant(7, &PBIORL)
#define SDA_OUTPUT __set_bit_constant(7, &PBIORL)
#define SDA (PBDR & PB7)
#define SCL_INPUT (PBIOR &= ~PB13)
#define SCL_OUTPUT (PBIOR |= PB13)
#define SCL_LO (PBDR &= ~PB13)
#define SCL_HI (PBDR |= PB13)
#define SCL_INPUT __clear_bit_constant(13-8, &PBIORH)
#define SCL_OUTPUT __set_bit_constant(13-8, &PBIORH)
#define SCL_LO __clear_bit_constant(13-8, &PBDRH)
#define SCL_HI __set_bit_constant(13-8, &PBDRH)
#define SCL (PBDR & PB13)
/* arbitrary delay loop */
@ -81,11 +82,11 @@ void i2c_init(void)
PBCR2 &= ~0xcc00; /* PB5 abd PB7 */
/* PB5 is "MAS enable". make it output and high */
PBIOR |= PB5;
PBDR |= PB5;
__set_bit_constant(5, &PBIORL);
__set_bit_constant(5, &PBDRL);
/* Set the clock line to an output */
PBIOR |= PB13;
/* Set the clock line PB13 to an output */
__set_bit_constant(13-8, &PBIORH);
SDA_OUTPUT;
SDA_HI;
@ -103,9 +104,13 @@ void i2c_ack(int bit)
SCL_LO; /* Set the clock low */
if ( bit )
{
SDA_HI;
}
else
{
SDA_LO;
}
SCL_INPUT; /* Set the clock to input */
while(!SCL) /* and wait for the MAS to release it */
@ -153,9 +158,13 @@ void i2c_outb(unsigned char byte)
/* clock out each bit, MSB first */
for ( i=0x80; i; i>>=1 ) {
if ( i & byte )
{
SDA_HI;
}
else
{
SDA_LO;
}
SCL_HI;
SCL_LO;
}