示例#1
0
文件: i2c.c 项目: afranceschi/SDR
/**
 * @brief Process an i2c transaction.
 *
 * Transactions are composed of one or more i2c_msg's, and may be read
 * or write tranfers.  Multiple i2c_msg's will generate a repeated
 * start in between messages.
 *
 * @param dev I2C device
 * @param msgs Messages to send/receive
 * @param num Number of messages to send/receive
 * @param timeout Bus idle timeout in milliseconds before aborting the
 *                transfer.  0 denotes no timeout.
 * @return 0 on success,
 *         I2C_ERROR_PROTOCOL if there was a protocol error,
 *         I2C_ERROR_TIMEOUT if the transfer timed out.
 */
int32 i2c_master_xfer(i2c_dev *dev,
                      i2c_msg *msgs,
                      uint16 num,
                      uint32 timeout) {
    int32 rc;

    ASSERT(dev->state == I2C_STATE_IDLE);

    dev->msg = msgs;
    dev->msgs_left = num;
    dev->timestamp = systick_uptime();
    dev->state = I2C_STATE_BUSY;

    i2c_enable_irq(dev, I2C_IRQ_EVENT);
    i2c_start_condition(dev);

    rc = wait_for_state_change(dev, I2C_STATE_XFER_DONE, timeout);
    if (rc < 0) {
        goto out;
    }

    dev->state = I2C_STATE_IDLE;
out:
    return rc;
}
示例#2
0
int i2c_master_recv_data(unsigned int addr,
			unsigned char *data, unsigned int len)
{
	unsigned int i = 0;
	int ret = 0;

	ret = i2c_set_master();	// get iic bus, as bus master;
	if (ret) {
		putstring("\nget i2c bus error\n");
		return ret;	// error while getting bus
	}

	i2c_enable_irq();
	i2c_message_start(addr, 1);
	while (1) {
		i++;
		if (i == len) {		// last byte
			i2c_disable_ack();
			break;
		}
		*data++ = IICDS;
		IICCON &= ~(1 << 4);	// resume trasmit
		// TODO dealy ??
		for (ret = 0; ret < 30; ret++) ;	// setup time
	}

	/* last byte */
	*data++ = IICDS;
	IICCON &= ~(1 << 4);	// resume trasmit

	// TODO dealy ??
	for (ret = 0; ret < 30; ret++) ; // setup time
	return len;
}
示例#3
0
文件: i2c.c 项目: boltonja/armduino
/**
 * @brief Initialize an I2C device as bus master
 * @param dev Device to enable
 * @param flags Bitwise or of the following I2C options:
 *              I2C_FAST_MODE: 400 khz operation,
 *              I2C_DUTY_16_9: 16/9 Tlow/Thigh duty cycle (only applicable for
 *                             fast mode),
 *              I2C_BUS_RESET: Reset the bus and clock out any hung slaves on
 *                             initialization,
 *              I2C_10BIT_ADDRESSING: Enable 10-bit addressing,
 *              I2C_REMAP: (deprecated, STM32F1 only) Remap I2C1 to SCL/PB8
 *                         SDA/PB9.
 */
void i2c_master_enable(i2c_dev *dev, uint32 flags) {
	/* Reset the bus. Clock out any hung slaves. */
	if (flags & I2C_BUS_RESET) {
		fooprint("i2c_master_enable: calling i2c_bus_reset");
		i2c_bus_reset(dev);
	}
	fooprint("i2c_master_enable: entry");
	/* PE must be disabled to configure the device */
	// ASSERT(!(dev->regs->CR1 & I2C_CR1_PE));

	/* Ugh */
	//_i2c_handle_remap(dev, flags);

	fooprint("i2c_master_enable: calling i2c_init");
	/* Turn on clock and set GPIO modes */
	i2c_init(dev);
	
	fooprint("i2c_master_enable: calling i2c_config_gpios");
	i2c_config_gpios(dev);

	fooprint("i2c_master_enable: calling set_freq_scl");
	/* Configure clock and rise time */
	set_freq_scl(dev, flags);

	fooprint("i2c_master_enable: calling nvic_irq_enable(ev)");
	/* Enable event and buffer interrupts */
	nvic_irq_enable(dev->ev_nvic_line);
	fooprint("i2c_master_enable: calling nvic_irq_enable(er)");
	nvic_irq_enable(dev->er_nvic_line);
	
	//gutted
	
	fooprint("i2c_master_enable: calling i2c_enable_irq");
	i2c_enable_irq(dev, I2C_CFGR_STOIEN_MASK | I2C_CFGR_ACKIEN_MASK | I2C_CFGR_RXIEN_MASK | I2C_CFGR_TXIEN_MASK | I2C_CFGR_STAIEN_MASK | I2C_CFGR_ARBLIEN_MASK);

	/* Make it go! */
	
	fooprint("i2c_master_enable: calling i2c_peripheral_enable");
	//gutted

	i2c_peripheral_enable(dev);




	dev->state = I2C_STATE_IDLE;
	fooprint("i2c_master_enable: exit, dev-state = I2C_STATE_IDLE");
}
示例#4
0
文件: i2c.c 项目: afranceschi/SDR
/**
 * @brief Initialize an I2C device as bus master
 * @param dev Device to enable
 * @param flags Bitwise or of the following I2C options:
 *              I2C_FAST_MODE: 400 khz operation,
 *              I2C_DUTY_16_9: 16/9 Tlow/Thigh duty cycle (only applicable for
 *                             fast mode),
 *              I2C_BUS_RESET: Reset the bus and clock out any hung slaves on
 *                             initialization,
 *              I2C_10BIT_ADDRESSING: Enable 10-bit addressing,
 *              I2C_REMAP: (deprecated, STM32F1 only) Remap I2C1 to SCL/PB8
 *                         SDA/PB9.
 */
void i2c_master_enable(i2c_dev *dev, uint32 flags) {
    /* PE must be disabled to configure the device */
    ASSERT(!(dev->regs->CR1 & I2C_CR1_PE));

    /* Ugh */
    _i2c_handle_remap(dev, flags);

    /* Reset the bus. Clock out any hung slaves. */
    if (flags & I2C_BUS_RESET) {
        i2c_bus_reset(dev);
    }

    /* Turn on clock and set GPIO modes */
    i2c_init(dev);
    i2c_config_gpios(dev);

    /* Configure clock and rise time */
    set_ccr_trise(dev, flags);

    /* Enable event and buffer interrupts */
    nvic_irq_enable(dev->ev_nvic_line);
    nvic_irq_enable(dev->er_nvic_line);
    i2c_enable_irq(dev, I2C_IRQ_EVENT | I2C_IRQ_BUFFER | I2C_IRQ_ERROR);

    /* Configure the slave unit */
    if (flags & I2C_SLAVE_DUAL_ADDRESS) {
        i2c_slave_dual_address_enable(dev);
    }

    if (flags & I2C_SLAVE_GENERAL_CALL) {
        i2c_slave_general_call_enable(dev);
    }

    /* store all of the flags */
    dev->config_flags = flags;

    /* Make it go! */
    i2c_peripheral_enable(dev);
    i2c_enable_ack(dev);

    dev->state = I2C_STATE_IDLE;
}
示例#5
0
文件: i2c.c 项目: afranceschi/SDR
/*
 * IRQ handler for I2C master. Handles transmission/reception.
 */
void _i2c_irq_handler(i2c_dev *dev) {
    /* WTFs:
     * - Where is I2C_MSG_10BIT_ADDR handled?
     */
    i2c_msg *msg = dev->msg;

    uint8 read = msg->flags & I2C_MSG_READ;

    uint32 sr1 = dev->regs->SR1;
    uint32 sr2 = dev->regs->SR2;
    I2C_CRUMB(IRQ_ENTRY, sr1, sr2);

    /*
     * Reset timeout counter
     */
    dev->timestamp = systick_uptime();

    /*
     * Add Slave support
     */

    /* Check to see if MSL master slave bit is set */
    if ((sr2 & I2C_SR2_MSL) != I2C_SR2_MSL) { /* 0 = slave mode 1 = master */

        /* Check for address match */
        if (sr1 & I2C_SR1_ADDR) {
            /* Find out which address was matched */
            /* Check the general call address first */
            if (sr2 & I2C_SR2_GENCALL) {
                dev->i2c_slave_msg->addr = 0;
            }
            /* We matched the secondary address */
            else if (sr2 & I2C_SR2_DUALF) {
                dev->i2c_slave_msg->addr = dev->regs->OAR2 & 0xFE;
            }
            /* We matched the primary address */
            else if ((sr2 & I2C_SR2_DUALF) != I2C_SR2_DUALF) {
                dev->i2c_slave_msg->addr = dev->regs->OAR1 & 0xFE;
            }
            /* Shouldn't get here */
            else {
                dev->i2c_slave_msg->addr = -1; /* uh oh */
            }

            /* if we have buffered io */
            if ((dev->config_flags & I2C_SLAVE_USE_RX_BUFFER) ||
                (dev->config_flags & I2C_SLAVE_USE_TX_BUFFER)) {

                /* if receiving then this would be a repeated start
                 *
                 *if we have some bytes already
                 */
                if ((dev->state == I2C_STATE_SL_RX) &&
                    (dev->i2c_slave_msg->xferred > 0)  &&
                    (dev->config_flags & I2C_SLAVE_USE_RX_BUFFER)) {
                    /* Call the callback with the contents of the data */
                    if (dev->i2c_slave_recv_callback != NULL) {
                        (*(dev->i2c_slave_recv_callback))(dev->i2c_slave_msg);
                    }
                }

                /* Reset the message back to defaults.
                 * We are starting a new message
                 */
                dev->i2c_slave_msg->flags = 0;
                dev->i2c_slave_msg->length = 0;
                dev->i2c_slave_msg->xferred = 0;
                dev->msgs_left = 0;
                dev->timestamp = systick_uptime();

                /* We have been addressed with SLA+R so
                 * the master wants us to transmit
                 */
                if ((sr1 & I2C_SR1_TXE) &&
                    (dev->config_flags & I2C_SLAVE_USE_TX_BUFFER)) {
                    /* Call the transmit callback so it can populate the msg
                     * data with the bytes to go
                     */
                    if (dev->i2c_slave_transmit_callback != NULL) {
                        (*(dev->i2c_slave_transmit_callback))(dev->i2c_slave_msg);
                    }
                }
                dev->state = I2C_STATE_BUSY;
            }

            sr1 = sr2 = 0;
        }
        
         /* EV3: Master requesting data from slave. Transmit a byte*/
        if (sr1 & I2C_SR1_TXE) {
            if (dev->config_flags & I2C_SLAVE_USE_TX_BUFFER) {
                if (dev->i2c_slave_msg->xferred >= dev->i2c_slave_msg->length) {
                    /* End of the transmit buffer? If so we NACK */
                    i2c_disable_ack(dev);
                    /* We have to either issue a STOP or write something here.
                     * STOP here seems to screw up some masters,
                     * For now padding with 0
                     */
                    i2c_write(dev, 0);
                    /*i2c_stop_condition(dev); // This is causing bus lockups way more than it should !? Seems some I2C master devices freak out here*/
                }
                else
                {
                    /* NACk the last byte */
                    if (dev->i2c_slave_msg->xferred == dev->i2c_slave_msg->length-1) {
                        i2c_disable_ack(dev);
                    }
                    else {
                        i2c_enable_ack(dev);
                    }
                    i2c_write(dev, dev->i2c_slave_msg->data[dev->i2c_slave_msg->xferred++]);
                }
            }
            else
            {
                /* Call the callback to get the data we need.
                 * The callback is expected to write using i2c_write(...)
                 * If the slave is going to terminate the transfer, this function should
                 * also do a NACK on the last byte!
                 */
                if (dev->i2c_slave_transmit_callback != NULL) (*(dev->i2c_slave_transmit_callback))(dev->i2c_slave_msg);
            }

            dev->state = I2C_STATE_BUSY;
            sr1 = sr2 = 0;
        }
        
        /* EV2: Slave received data from a master. Get from DR */
        if (sr1 & I2C_SR1_RXNE) {
            if (dev->config_flags & I2C_SLAVE_USE_RX_BUFFER) {
                /* Fill the buffer with the contents of the data register */
                /* These is potential for buffer overflow here, so we should
                 * really store the size of the array. This is expensive in
                 * the ISR so left out for now. We must trust the implementor!
                 */
                dev->i2c_slave_msg->data[dev->i2c_slave_msg->xferred++] = dev->regs->DR;
                dev->i2c_slave_msg->length++;
            }
            else  {
                /* Call the callback with the contents of the data */
                dev->i2c_slave_msg->data[0] = dev->regs->DR;
                if (dev->i2c_slave_recv_callback != NULL) (*(dev->i2c_slave_recv_callback))(dev->i2c_slave_msg);
            }
            dev->state = I2C_STATE_SL_RX;
            sr1 = sr2 = 0;
        }

        /* EV4: Slave has detected a STOP condition on the bus */
        if (sr1 & I2C_SR1_STOPF) {
            dev->regs->CR1 |= I2C_CR1_PE;

            if ((dev->config_flags & I2C_SLAVE_USE_RX_BUFFER) ||
                (dev->config_flags & I2C_SLAVE_USE_TX_BUFFER)) {

                /* The callback with the data will happen on a NACK of the last data byte.
                 * This is handled in the error IRQ (AF bit)
                 */
                /* Handle the case where the master misbehaves by sending no NACK */
                if (dev->state != I2C_STATE_IDLE) {
                    if (dev->state == I2C_STATE_SL_RX) {
                        if (dev->i2c_slave_recv_callback != NULL) (*(dev->i2c_slave_recv_callback))(dev->i2c_slave_msg);
                    }
                    else {
                        if (dev->i2c_slave_transmit_callback != NULL) (*(dev->i2c_slave_transmit_callback))(dev->i2c_slave_msg);
                    }
                }
            }

            sr1 = sr2 = 0;
            dev->state = I2C_STATE_IDLE;
        }

        return;
    }
    
    /*
     * EV5: Start condition sent
     */
    if (sr1 & I2C_SR1_SB) {
        msg->xferred = 0;
        i2c_enable_irq(dev, I2C_IRQ_BUFFER);

        /*
         * Master receiver
         */
        if (read) {
            i2c_enable_ack(dev);
        }

        i2c_send_slave_addr(dev, msg->addr, read);
        sr1 = sr2 = 0;
    }

    /*
     * EV6: Slave address sent
     */
    if (sr1 & I2C_SR1_ADDR) {
        /*
         * Special case event EV6_1 for master receiver.
         * Generate NACK and restart/stop condition after ADDR
         * is cleared.
         */
        if (read) {
            if (msg->length == 1) {
                i2c_disable_ack(dev);
                if (dev->msgs_left > 1) {
                    i2c_start_condition(dev);
                    I2C_CRUMB(RX_ADDR_START, 0, 0);
                } else {
                    i2c_stop_condition(dev);
                    I2C_CRUMB(RX_ADDR_STOP, 0, 0);
                }
            }
        } else {
            /*
             * Master transmitter: write first byte to fill shift
             * register.  We should get another TXE interrupt
             * immediately to fill DR again.
             */
            if (msg->length != 1) {
                i2c_write(dev, msg->data[msg->xferred++]);
            }
        }
        sr1 = sr2 = 0;
    }

    /*
     * EV8: Master transmitter
     * Transmit buffer empty, but we haven't finished transmitting the last
     * byte written.
     */
    if ((sr1 & I2C_SR1_TXE) && !(sr1 & I2C_SR1_BTF)) {
        I2C_CRUMB(TXE_ONLY, 0, 0);
        if (dev->msgs_left) {
            i2c_write(dev, msg->data[msg->xferred++]);
            if (msg->xferred == msg->length) {
                /*
                 * End of this message. Turn off TXE/RXNE and wait for
                 * BTF to send repeated start or stop condition.
                 */
                i2c_disable_irq(dev, I2C_IRQ_BUFFER);
                dev->msgs_left--;
            }
        } else {
            /*
             * This should be impossible...
             */
            ASSERT(0);
        }
        sr1 = sr2 = 0;
    }

    /*
     * EV8_2: Master transmitter
     * Last byte sent, program repeated start/stop
     */
    if ((sr1 & I2C_SR1_TXE) && (sr1 & I2C_SR1_BTF)) {
        I2C_CRUMB(TXE_BTF, 0, 0);
        if (dev->msgs_left) {
            I2C_CRUMB(TEST, 0, 0);
            /*
             * Repeated start insanity: We can't disable ITEVTEN or else SB
             * won't interrupt, but if we don't disable ITEVTEN, BTF will
             * continually interrupt us. What the f**k ST?
             */
            i2c_start_condition(dev);
            while (!(dev->regs->SR1 & I2C_SR1_SB))
                ;
            dev->msg++;
        } else {
            i2c_stop_condition(dev);

            /*
             * Turn off event interrupts to keep BTF from firing until
             * the end of the stop condition. Why on earth they didn't
             * have a start/stop condition request clear BTF is beyond
             * me.
             */
            i2c_disable_irq(dev, I2C_IRQ_EVENT);
            I2C_CRUMB(STOP_SENT, 0, 0);
            dev->state = I2C_STATE_XFER_DONE;
        }
        sr1 = sr2 = 0;
    }

    /*
     * EV7: Master Receiver
     */
    if (sr1 & I2C_SR1_RXNE) {
        I2C_CRUMB(RXNE_ONLY, 0, 0);
        msg->data[msg->xferred++] = dev->regs->DR;

        /*
         * EV7_1: Second to last byte in the reception? Set NACK and generate
         * stop/restart condition in time for the last byte. We'll get one more
         * RXNE interrupt before shutting things down.
         */
        if (msg->xferred == (msg->length - 1)) {
            i2c_disable_ack(dev);
            if (dev->msgs_left > 2) {
                i2c_start_condition(dev);
                I2C_CRUMB(RXNE_START_SENT, 0, 0);
            } else {
                i2c_stop_condition(dev);
                I2C_CRUMB(RXNE_STOP_SENT, 0, 0);
            }
        } else if (msg->xferred == msg->length) {
            dev->msgs_left--;
            if (dev->msgs_left == 0) {
                /*
                 * We're done.
                 */
                I2C_CRUMB(RXNE_DONE, 0, 0);
                dev->state = I2C_STATE_XFER_DONE;
            } else {
                dev->msg++;
            }
        }
    }

}
示例#6
0
/**
 * @brief Initialize an I2C device as bus master
 * @param dev Device to enable
 * @param flags Bitwise or of the following I2C options:
 *              I2C_FAST_MODE: 400 khz operation,
 *              I2C_DUTY_16_9: 16/9 Tlow/Thigh duty cycle (only applicable for
 *                             fast mode),
 *              I2C_BUS_RESET: Reset the bus and clock out any hung slaves on
 *                             initialization,
 *              I2C_10BIT_ADDRESSING: Enable 10-bit addressing,
 *              I2C_REMAP: Remap I2C1 to SCL/PB8 SDA/PB9.
 */
void i2c_master_enable(i2c_dev *dev, uint32 flags) {
#define I2C_CLK                (STM32_PCLK1/1000000)
    uint32 ccr   = 0;
    uint32 trise = 0;

    /* PE must be disabled to configure the device */
    ASSERT(!(dev->regs->CR1 & I2C_CR1_PE));

    if ((dev == I2C1) && (flags & I2C_REMAP)) {
        afio_remap(AFIO_REMAP_I2C1);
        I2C1->sda_pin = 9;
        I2C1->scl_pin = 8;
    }

    /* Reset the bus. Clock out any hung slaves. */
    if (flags & I2C_BUS_RESET) {
        i2c_bus_reset(dev);
    }

    /* Turn on clock and set GPIO modes */
    i2c_init(dev);
    gpio_set_mode(dev->gpio_port, dev->sda_pin, GPIO_AF_OUTPUT_OD);
    gpio_set_mode(dev->gpio_port, dev->scl_pin, GPIO_AF_OUTPUT_OD);

    /* I2C1 and I2C2 are fed from APB1, clocked at 36MHz */
    i2c_set_input_clk(dev, I2C_CLK);

    if (flags & I2C_FAST_MODE) {
        ccr |= I2C_CCR_FS;

        if (flags & I2C_DUTY_16_9) {
            /* Tlow/Thigh = 16/9 */
            ccr |= I2C_CCR_DUTY;
            ccr |= STM32_PCLK1/(400000 * 25);
        } else {
            /* Tlow/Thigh = 2 */
            ccr |= STM32_PCLK1/(400000 * 3);
        }

        trise = (300 * (I2C_CLK)/1000) + 1;
    } else {
        /* Tlow/Thigh = 1 */
        ccr = STM32_PCLK1/(100000 * 2);
        trise = I2C_CLK + 1;
    }

    /* Set minimum required value if CCR < 1*/
    if ((ccr & I2C_CCR_CCR) == 0) {
        ccr |= 0x1;
    }

    i2c_set_clk_control(dev, ccr);
    i2c_set_trise(dev, trise);

    /* Enable event and buffer interrupts */
    nvic_irq_enable(dev->ev_nvic_line);
    nvic_irq_enable(dev->er_nvic_line);
    i2c_enable_irq(dev, I2C_IRQ_EVENT | I2C_IRQ_BUFFER | I2C_IRQ_ERROR);

    /*
     * Important STM32 Errata:
     *
     * See STM32F10xx8 and STM32F10xxB Errata sheet (Doc ID 14574 Rev 8),
     * Section 2.11.1, 2.11.2.
     *
     * 2.11.1:
     * When the EV7, EV7_1, EV6_1, EV6_3, EV2, EV8, and EV3 events are not
     * managed before the current byte is being transferred, problems may be
     * encountered such as receiving an extra byte, reading the same data twice
     * or missing data.
     *
     * 2.11.2:
     * In Master Receiver mode, when closing the communication using
     * method 2, the content of the last read data can be corrupted.
     *
     * If the user software is not able to read the data N-1 before the STOP
     * condition is generated on the bus, the content of the shift register
     * (data N) will be corrupted. (data N is shifted 1-bit to the left).
     *
     * ----------------------------------------------------------------------
     *
     * In order to ensure that events are not missed, the i2c interrupt must
     * not be preempted. We set the i2c interrupt priority to be the highest
     * interrupt in the system (priority level 0). All other interrupts have
     * been initialized to priority level 16. See nvic_init().
     */
    nvic_irq_set_priority(dev->ev_nvic_line, 0);
    nvic_irq_set_priority(dev->er_nvic_line, 0);

    /* Make it go! */
    i2c_peripheral_enable(dev);

    dev->state = I2C_STATE_IDLE;
}
示例#7
0
/**
 * @brief IRQ handler for I2C master. Handles transmission/reception.
 * @param dev I2C device
 */
static void i2c_irq_handler(i2c_dev *dev) {
    i2c_msg *msg = dev->msg;

    uint8 read = msg->flags & I2C_MSG_READ;

    uint32 sr1 = dev->regs->SR1;
    uint32 sr2 = dev->regs->SR2;
    I2C_CRUMB(IRQ_ENTRY, sr1, sr2);

    /*
     * Reset timeout counter
     */
    dev->timestamp = systick_uptime();

    /*
     * EV5: Start condition sent
     */
    if (sr1 & I2C_SR1_SB) {
        msg->xferred = 0;
        i2c_enable_irq(dev, I2C_IRQ_BUFFER);

        /*
         * Master receiver
         */
        if (read) {
            i2c_enable_ack(dev);
        }

        i2c_send_slave_addr(dev, msg->addr, read);
        sr1 = sr2 = 0;
    }

    /*
     * EV6: Slave address sent
     */
    if (sr1 & I2C_SR1_ADDR) {
        /*
         * Special case event EV6_1 for master receiver.
         * Generate NACK and restart/stop condition after ADDR
         * is cleared.
         */
        if (read) {
            if (msg->length == 1) {
                i2c_disable_ack(dev);
                if (dev->msgs_left > 1) {
                    i2c_start_condition(dev);
                    I2C_CRUMB(RX_ADDR_START, 0, 0);
                } else {
                    i2c_stop_condition(dev);
                    I2C_CRUMB(RX_ADDR_STOP, 0, 0);
                }
            }
        } else {
            /*
             * Master transmitter: write first byte to fill shift
             * register.  We should get another TXE interrupt
             * immediately to fill DR again.
             */
            if (msg->length != 1) {
                i2c_write(dev, msg->data[msg->xferred++]);
            }
        }
        sr1 = sr2 = 0;
    }

    /*
     * EV8: Master transmitter
     * Transmit buffer empty, but we haven't finished transmitting the last
     * byte written.
     */
    if ((sr1 & I2C_SR1_TXE) && !(sr1 & I2C_SR1_BTF)) {
        I2C_CRUMB(TXE_ONLY, 0, 0);
        if (dev->msgs_left) {
            i2c_write(dev, msg->data[msg->xferred++]);
            if (msg->xferred == msg->length) {
                /*
                 * End of this message. Turn off TXE/RXNE and wait for
                 * BTF to send repeated start or stop condition.
                 */
                i2c_disable_irq(dev, I2C_IRQ_BUFFER);
                dev->msgs_left--;
            }
        } else {
            /*
             * This should be impossible...
             */
            throb();
        }
        sr1 = sr2 = 0;
    }

    /*
     * EV8_2: Master transmitter
     * Last byte sent, program repeated start/stop
     */
    if ((sr1 & I2C_SR1_TXE) && (sr1 & I2C_SR1_BTF)) {
        I2C_CRUMB(TXE_BTF, 0, 0);
        if (dev->msgs_left) {
            I2C_CRUMB(TEST, 0, 0);
            /*
             * Repeated start insanity: We can't disable ITEVTEN or else SB
             * won't interrupt, but if we don't disable ITEVTEN, BTF will
             * continually interrupt us. What the f**k ST?
             */
            i2c_start_condition(dev);
            while (!(dev->regs->SR1 & I2C_SR1_SB))
                ;
            dev->msg++;
        } else {
            i2c_stop_condition(dev);

            /*
             * Turn off event interrupts to keep BTF from firing until
             * the end of the stop condition. Why on earth they didn't
             * have a start/stop condition request clear BTF is beyond
             * me.
             */
            i2c_disable_irq(dev, I2C_IRQ_EVENT);
            I2C_CRUMB(STOP_SENT, 0, 0);
            dev->state = I2C_STATE_XFER_DONE;
        }
        sr1 = sr2 = 0;
    }

    /*
     * EV7: Master Receiver
     */
    if (sr1 & I2C_SR1_RXNE) {
        I2C_CRUMB(RXNE_ONLY, 0, 0);
        msg->data[msg->xferred++] = dev->regs->DR;

        /*
         * EV7_1: Second to last byte in the reception? Set NACK and generate
         * stop/restart condition in time for the last byte. We'll get one more
         * RXNE interrupt before shutting things down.
         */
        if (msg->xferred == (msg->length - 1)) {
            i2c_disable_ack(dev);
            if (dev->msgs_left > 2) {
                i2c_start_condition(dev);
                I2C_CRUMB(RXNE_START_SENT, 0, 0);
            } else {
                i2c_stop_condition(dev);
                I2C_CRUMB(RXNE_STOP_SENT, 0, 0);
            }
        } else if (msg->xferred == msg->length) {
            dev->msgs_left--;
            if (dev->msgs_left == 0) {
                /*
                 * We're done.
                 */
                I2C_CRUMB(RXNE_DONE, 0, 0);
                dev->state = I2C_STATE_XFER_DONE;
            } else {
                dev->msg++;
            }
        }
    }
}