Quadrotor from scratch
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3.6 KiB

#include "i2c.h"
#include "interrupt.h"
#define I2CBASE 0xE001C000
#define I2CONSET 0x00
#define I2STAT 0x04
#define I2DAT 0x08
#define I2ADR 0x0c
#define I2SCLH 0x10
#define I2SCLL 0x14
#define I2CONCLR 0x18
#define IREG(x) (((volatile unsigned char *)I2CBASE)[x])
#define IWREG(x) (((volatile unsigned int *)I2CBASE)[(x)/sizeof(unsigned int)])
#define AAFLAG (1<<2)
#define SIFLAG (1<<3)
#define STOFLAG (1<<4)
#define STAFLAG (1<<5)
#define SI (IREG(I2CONSET) & SIFLAG)
void __attribute__((interrupt("IRQ"))) i2c_interrupt_handler(void);
struct i2c_transaction *i2c_transaction;
int i2c_bytes;
void init_i2c(void)
{
IREG(I2CONSET) = 0x40; /* Enable I2C ready for Master Tx */
/* Set up for just under 400kHz */
#ifdef I2C_FAST
IWREG(I2SCLL) = (25 * 100);
IWREG(I2SCLH) = (12 * 100);
#else
IWREG(I2SCLL) = 73; /* ~100kHz */
IWREG(I2SCLH) = 73;
#endif
interrupt_register(I2C0, i2c_interrupt_handler);
}
int i2c_conreg(void)
{
return IREG(I2CONSET);
}
int i2c_statreg(void)
{
return IREG(I2STAT);
}
bool i2c_busy(void)
{
return i2c_transaction != NULL;
}
bool i2c_start_transaction(struct i2c_transaction *t)
{
if (i2c_transaction)
return FALSE;
i2c_transaction = t;
*(t->result) = I2C_IN_PROGRESS;
/* Paranoia in case we left things in a bad state */
IREG(I2CONCLR) = STOFLAG | STAFLAG;
/* Set it all going */
IREG(I2CONSET) = STAFLAG;
return TRUE;
}
void __attribute__((interrupt("IRQ"))) i2c_interrupt_handler(void)
{
int stat = IREG(I2STAT);
if (!i2c_transaction) {
IREG(I2CONSET) = STOFLAG;
IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
interrupt_clear();
return;
}
switch (stat) {
case 0x08: /* START transmitted */
case 0x10: /* repeated START transmitted */
IREG(I2DAT) = i2c_transaction->address;
IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
i2c_bytes = 0;
break;
case 0x18: /* SA+W transmitted, ACK received */
case 0x28: /* data transmitted, ACK received */
if (i2c_bytes < i2c_transaction->bytes) {
IREG(I2DAT) = i2c_transaction->data[i2c_bytes++];
IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
} else {
*(i2c_transaction->result) = I2C_SUCCESS;
if (i2c_transaction->next) {
i2c_transaction = i2c_transaction->next;
i2c_bytes = 0;
IREG(I2CONSET) = STAFLAG;
IREG(I2CONCLR) = STOFLAG | AAFLAG | SIFLAG;
} else {
i2c_transaction = NULL;
IREG(I2CONSET) = STOFLAG;
IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
}
}
break;
case 0x50: /* data received, ACK returned */
i2c_transaction->data[i2c_bytes++] = IREG(I2DAT);
/* fall through */
case 0x40: /* SA+R transmitted, ACK received */
if (i2c_bytes < (i2c_transaction->bytes-1)) {
IREG(I2CONSET) = AAFLAG;
IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG;
} else {
IREG(I2CONCLR) = STAFLAG | STOFLAG | SIFLAG
| AAFLAG;
}
break;
case 0x58: /* data received, NACK returned */
i2c_transaction->data[i2c_bytes] = IREG(I2DAT);
*(i2c_transaction->result) = I2C_SUCCESS;
if (i2c_transaction->next) {
i2c_transaction = i2c_transaction->next;
i2c_bytes = 0;
IREG(I2CONSET) = STAFLAG;
IREG(I2CONCLR) = STOFLAG | AAFLAG | SIFLAG;
} else {
i2c_transaction = NULL;
IREG(I2CONSET) = STOFLAG;
IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
}
break;
case 0x20: /* SA+W transmitted, NACK received */
case 0x30: /* data transmitted, NACK received */
case 0x48: /* SA+R transmitted, NACK received */
case 0x38: /* arbitration lost during SA+W or data */
case 0x00: /* bus error */
*(i2c_transaction->result) = I2C_FAIL;
i2c_transaction = NULL;
IREG(I2CONSET) = STOFLAG;
IREG(I2CONCLR) = STAFLAG | AAFLAG | SIFLAG;
break;
/* We don't handle slave mode */
}
interrupt_clear();
}