devs/foxbox
1
0
Fork 0
forked from len0rd/rockbox
Code Pull requests Activity

Added proper clock-stretching to the pcf50606 I2C driver

Browse source 
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@8018 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Linus Nielsen Feltzing 2005-11-21 02:13:14 +00:00
parent 5124844e32
commit dcb8df5180
1 changed files with 4 additions and 34 deletions
Download patch file Download diff file Expand all files Collapse all files

36
firmware/drivers/pcf50606.c
View file

@ -38,7 +38,7 @@
#define SCL_INPUT and_l(~0x00001000, &GPIO_ENABLE) #define SCL_INPUT and_l(~0x00001000, &GPIO_ENABLE)
#define SCL_OUTPUT or_l( 0x00001000, &GPIO_ENABLE) #define SCL_OUTPUT or_l( 0x00001000, &GPIO_ENABLE)
#define SCL_LO and_l(~0x00001000, &GPIO_OUT) #define SCL_LO and_l(~0x00001000, &GPIO_OUT)
#define SCL_HI or_l( 0x00001000, &GPIO_OUT) #define SCL_HI SCL_INPUT;while(!SCL){};or_l(0x1000, &GPIO_OUT);SCL_OUTPUT
#define SCL ( 0x00001000 & GPIO_READ) #define SCL ( 0x00001000 & GPIO_READ)
/* delay loop to achieve 400kHz at 120MHz CPU frequency */ /* delay loop to achieve 400kHz at 120MHz CPU frequency */
@ -68,28 +68,13 @@ static void pcf50606_i2c_stop(void)
static void pcf50606_i2c_ack(bool ack) static void pcf50606_i2c_ack(bool ack)
{ {
/* Here's the deal. The slave is slow, and sometimes needs to wait
before it can receive the acknowledge. Therefore it forces the clock
low until it is ready. We need to poll the clock line until it goes
high before we release the ack.
In their infinite wisdom, iriver didn't pull up the SCL line, so
we have to drive the SCL high repeatedly to simulate a pullup. */
SCL_LO; /* Set the clock low */ SCL_LO; /* Set the clock low */
if(ack) if(ack)
SDA_LO; SDA_LO;
else else
SDA_HI; SDA_HI;
SCL_INPUT; /* Set the clock to input */ SCL_HI;
while(!SCL) /* and wait for the slave to release it */
{
SCL_OUTPUT; /* Set the clock to output */
SCL_HI;
SCL_INPUT; /* Set the clock to input */
DELAY;
}
DELAY; DELAY;
SCL_OUTPUT; SCL_OUTPUT;
@ -100,23 +85,8 @@ static int pcf50606_i2c_getack(void)
{ {
int ret = 1; int ret = 1;
/* Here's the deal. The slave is slow, and sometimes needs to wait
before it can send the acknowledge. Therefore it forces the clock
low until it is ready. We need to poll the clock line until it goes
high before we read the ack.
In their infinite wisdom, iriver didn't pull up the SCL line, so
we have to drive the SCL high repeatedly to simulate a pullup. */
SDA_INPUT; /* And set to input */ SDA_INPUT; /* And set to input */
SCL_INPUT; /* Set the clock to input */ SCL_HI;
while(!SCL) /* and wait for the slave to release it */
{
SCL_OUTPUT; /* Set the clock to output */
SCL_HI;
SCL_INPUT; /* Set the clock to input */
DELAY;
}
if (SDA) if (SDA)
/* ack failed */ /* ack failed */