me ne sono accorto.. ora devo andar a dare da mangiare alle anatre (!), più tardi gioco con le funzioni usate dal multiwii:
// ************************************************************************************************************
// I2C general functions
// ************************************************************************************************************
// Mask prescaler bits : only 5 bits of TWSR defines the status of each I2C request
#define TW_STATUS_MASK (1<<TWS7) | (1<<TWS6) | (1<<TWS5) | (1<<TWS4) | (1<<TWS3)
#define TW_STATUS (TWSR & TW_STATUS_MASK)
void i2c_init(void) {
#if defined(INTERNAL_I2C_PULLUPS)
I2C_PULLUPS_ENABLE
#else
I2C_PULLUPS_DISABLE
#endif
TWSR = 0; // no prescaler => prescaler = 1
TWBR = ((16000000L / I2C_SPEED) - 16) / 2; // change the I2C clock rate
TWCR = 1<<TWEN; // enable twi module, no interrupt
}
void i2c_rep_start(uint8_t address) {
TWCR = (1<<TWINT) | (1<<TWSTA) | (1<<TWEN) | (1<<TWSTO); // send REPEAT START condition
waitTransmissionI2C(); // wait until transmission completed
checkStatusI2C(); // check value of TWI Status Register
TWDR = address; // send device address
TWCR = (1<<TWINT) | (1<<TWEN);
waitTransmissionI2C(); // wail until transmission completed
checkStatusI2C(); // check value of TWI Status Register
}
void i2c_rep_stop(void) {
TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
waitTransmissionI2C();
checkStatusI2C();
}
void i2c_write(uint8_t data ) {
TWDR = data; // send data to the previously addressed device
TWCR = (1<<TWINT) | (1<<TWEN);
waitTransmissionI2C(); // wait until transmission completed
checkStatusI2C(); // check value of TWI Status Register
}
uint8_t i2c_readAck() {
TWCR = (1<<TWINT) | (1<<TWEN) | (1<<TWEA);
waitTransmissionI2C();
return TWDR;
}
uint8_t i2c_readNak(void) {
TWCR = (1<<TWINT) | (1<<TWEN);
waitTransmissionI2C();
return TWDR;
}
void waitTransmissionI2C() {
uint8_t count = 255;
while (count-->0 && !(TWCR & (1<<TWINT)) );
if (count<2) { //we are in a blocking state => we don't insist
TWCR = 0; //and we force a reset on TWINT register
neutralizeTime = micros(); //we take a timestamp here to neutralize the value during a short delay after the hard reset
}
}
void checkStatusI2C() {
if ( TW_STATUS == 0xF8) { //TW_NO_INFO : this I2C error status indicates a wrong I2C communication.
// WMP does not respond anymore => we do a hard reset. I did not find another way to solve it. It takes only 13ms to reset and init to WMP or WMP+NK
TWCR = 0;
if (!GYRO) {
POWERPIN_OFF //switch OFF WMP
delay(1);
POWERPIN_ON //switch ON WMP
delay(10);
WMP_init(0);
}
neutralizeTime = micros(); //we take a timestamp here to neutralize the WMP or WMP+NK values during a short delay after the hard reset
}
}
void i2c_getSixRawADC(uint8_t add, uint8_t reg) {
i2c_rep_start(add);
i2c_write(reg); // Start multiple read at the reg register
i2c_rep_start(add +1); // I2C read direction => I2C address + 1
for(uint8_t i = 0; i < 5; i++) {
rawADC[i]=i2c_readAck();}
rawADC[5]= i2c_readNak();
}
void i2c_writeReg(uint8_t add, uint8_t reg, uint8_t val) {
i2c_rep_start(add+0); // I2C write direction
i2c_write(reg); // register selection
i2c_write(val); // value to write in register
}
uint8_t i2c_readReg(uint8_t add, uint8_t reg) {
i2c_rep_start(add+0); // I2C write direction
i2c_write(reg); // register selection
i2c_rep_start(add+1); // I2C read direction
return i2c_readNak(); // Read single register and return value
}
per esempio waitTransmissionI2C è bloccante, fa un reset di twint, ma non ho capito
1: perchè l'if (count<2) (notare il ; dopo il while, quindi l'if è fuori dal corpo di esso.
2: se fa quel reset, non deve reinizializzare la comunicazione?
devo ancora leggermi bene tutto il codice per capire come funziona questo protocollo, però piuttosto che fare una wait transmission alla fine, non conviene farla all'inizio (se la flag che sono stati inviati dati è settata a true)? in questo modo si rimarrebbe bloccati molto meno tempo.
per il resto devo ancora leggere bene, mi sembra ok(ricordo che NON conosco il protocollo i2c)