ref: c116550e6a41572796e4db65e4f6acbcb3d9d6f8
dir: /os/sa1110/i2cgpio.c/
/* * I2C master emulation using GPIO pins. * 7 bit addressing only. */ #include "u.h" #include "../port/lib.h" #include "mem.h" #include "dat.h" #include "fns.h" #include "../port/error.h" #include "io.h" #include "i2c.h" /* GPIO bitmasks */ static struct { Lock; ulong sda; ulong scl; } i2c; /* set pin level high by disabling output drive and allowing pull-up to work */ static void i2c_set(int pin) { GPIOREG->gpdr &= ~pin; /* configure pin as input */ } /* set pin level low with output drive */ static void i2c_clear(int pin) { GPIOREG->gpcr = pin; /* set pin output low */ GPIOREG->gpdr |= pin; /* configure pin as output */ } static int i2c_getack(void) { /* scl is low, sda is not defined */ i2c_set(i2c.sda); /* set data high */ timer_delay(US2TMR(3)); i2c_set(i2c.scl); /* raise clock */ timer_delay(US2TMR(5)); /* check for ack from slave! */ if (GPIOREG->gplr & i2c.sda) print("I2C: Warning did not get ack!\n"); i2c_clear(i2c.sda); /* lower data */ i2c_clear(i2c.scl); /* lower clock */ timer_delay(US2TMR(3)); /* scl is low, sda is low */ return 1; } static void i2c_putack(void) { /* scl is low, sda is not defined */ timer_delay(US2TMR(3)); /* lower data */ i2c_clear(i2c.sda); i2c_set(i2c.scl); /* pulse clock */ timer_delay(US2TMR(5)); i2c_clear(i2c.scl); /* lower clock */ timer_delay(US2TMR(3)); /* scl is low, sda is low */ } static void i2c_putbyte(uchar b) { uchar m; /* start condition has been sent */ /* scl is low, sda is low */ for(m=0x80; m; m >>= 1) { /* set data bit */ if(b&m) i2c_set(i2c.sda); else i2c_clear(i2c.sda); /* pulse clock */ timer_delay(US2TMR(3)); i2c_set(i2c.scl); timer_delay(US2TMR(5)); i2c_clear(i2c.scl); timer_delay(US2TMR(3)); } i2c_clear(i2c.sda); /* scl is low, sda is low */ } static uchar i2c_getbyte(void) { /* start condition, address and ack been done */ /* scl is low, sda is high */ uchar data = 0x00; int i; i2c_set(i2c.sda); for (i=7; i >= 0; i--) { timer_delay(US2TMR(3)); /* raise clock */ i2c_set(i2c.scl); timer_delay(US2TMR(5)); /* sample data */ if(GPIOREG->gplr & i2c.sda) data |= 1<<i; /* lower clock */ i2c_clear(i2c.scl); timer_delay(US2TMR(3)); } i2c_clear(i2c.sda); return data; } /* generate I2C start condition */ static int i2c_start(void) { /* check that both scl and sda are high */ if ((GPIOREG->gplr & (i2c.sda | i2c.scl)) != (i2c.sda | i2c.scl)) print("I2C: Bus not clear when attempting start condition\n"); i2c_clear(i2c.sda); /* lower sda */ timer_delay(US2TMR(5)); i2c_clear(i2c.scl); /* lower scl */ timer_delay(US2TMR(3)); return 1; } /* generate I2C stop condition */ static int i2c_stop(void) { /* clock is low, data is low */ timer_delay(US2TMR(3)); i2c_set(i2c.scl); timer_delay(US2TMR(5)); i2c_set(i2c.sda); timer_delay(MS2TMR(1)); /* ensure separation between commands */ return 1; } /* * external I2C interface */ /* write a byte over the i2c bus */ int i2c_write_byte(uchar addr, uchar data) { int rc = 0; ilock(&i2c); if(i2c_start() < 0) /* start condition */ rc = -1; i2c_putbyte(addr & 0xfe); /* address byte (LSB = 0 -> write) */ if (i2c_getack() < 0) /* get ack */ rc = -2; i2c_putbyte(data); /* data byte */ if (i2c_getack() < 0) /* get ack */ rc = -3; if (i2c_stop() < 0) rc = -4; /* stop condition */ iunlock(&i2c); return rc; } /* read a byte over the i2c bus */ int i2c_read_byte(uchar addr, uchar *data) { int rc = 0; ilock(&i2c); if(i2c_start() < 0) /* start condition */ rc = -1; i2c_putbyte(addr | 0x01); /* address byte (LSB = 1 -> read) */ if(i2c_getack() < 0) /* get ack */ rc = -2; *data = i2c_getbyte(); /* data byte */ i2c_putack(); /* put ack */ if (i2c_stop() < 0) /* stop condition */ rc = -4; iunlock(&i2c); return rc; } void i2c_reset(void) { /* initialise bitmasks */ i2c.sda = (1 << gpio_i2c_sda); i2c.scl = (1 << gpio_i2c_scl); /* ensure that both clock and data are high */ i2c_set(i2c.sda); i2c_set(i2c.scl); timer_delay(MS2TMR(5)); } /* * external pin set/clear interface */ uchar i2c_iactl[2] = { 0xff, 0xff }; /* defaults overridden in arch?????.c */ int i2c_setpin(int b) { int i = b>>3; ilock(&i2c); i2c_iactl[i] |= (1 << (b&7)); iunlock(&i2c); return i2c_write_byte(0x40 | (i << 1), i2c_iactl[i]); } int i2c_clrpin(int b) { int i = b>>3; ilock(&i2c); i2c_iactl[i] &= ~(1 << (b&7)); iunlock(&i2c); return i2c_write_byte(0x40 | (i << 1), i2c_iactl[i]); } int i2c_getpin(int b) { return (i2c_iactl[(b>>3)&1] & (1<<(b&7))) != 0; }