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diff --git a/libmaple/i2c.c b/libmaple/i2c.c
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--- /dev/null
+++ b/libmaple/i2c.c
@@ -0,0 +1,502 @@
+/* *****************************************************************************
+ * The MIT License
+ *
+ * Copyright (c) 2010 Perry Hung.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ * ****************************************************************************/
+
+/**
+ *  @brief 
+ *  TODO: Rejigger hard fault handler and error throbs to turn off all
+ *  interrupts and jump to error throb to reenable usb bootloader
+ */
+
+#include "libmaple.h"
+#include "rcc.h"
+#include "nvic.h"
+#include "gpio.h"
+#include "nvic.h"
+#include "i2c.h"
+#include "string.h"
+
+/* 2/17 Started 10pm-4am
+ * 2/19 Started 7pm-2am
+ * 2/20 Started 7pm-7pm
+ * 2/23 Started 8pm */
+
+static inline int32 wait_for_state_change(i2c_dev *dev, i2c_state state);
+
+i2c_dev i2c_dev1 = {
+    .regs         = (i2c_reg_map*)I2C1_BASE,
+    .gpio_port    = GPIOB_BASE,
+    .sda_pin      = 7,
+    .scl_pin      = 6,
+    .clk_line     = RCC_I2C1,
+    .ev_nvic_line = NVIC_I2C1_EV,
+    .er_nvic_line = NVIC_I2C1_ER,
+    .state        = I2C_STATE_IDLE
+};
+
+/**
+ * @brief IRQ handler for i2c master. Handles transmission/reception.
+ * @param dev i2c device
+ */
+
+void delay_us(uint32 us) {
+    /* So (2^32)/12 micros max, or less than 6 minutes */
+    us *= 12;
+
+    /* fudge for function call overhead */
+    us--;
+    asm volatile("   mov r0, %[us]          \n\t"
+            "1: subs r0, #1            \n\t"
+            "   bhi 1b                 \n\t"
+            :
+            : [us] "r" (us)
+            : "r0");
+}
+static inline void debug_toggle(uint32 delay) {
+    gpio_write_bit(GPIOA_BASE, 5, 1);
+    delay_us(delay);
+    gpio_write_bit(GPIOA_BASE, 5, 0);
+}
+
+struct crumb {
+    uint32 event;
+    uint32 sr1;
+    uint32 sr2;
+};
+
+static struct crumb crumbs[100];
+static uint32 cur_crumb = 0;
+
+static inline void leave_big_crumb(uint32 event, uint32 sr1, uint32 sr2) {
+    if (cur_crumb < 100) {
+        struct crumb *crumb = &crumbs[cur_crumb++];
+        crumb->event = event;
+        crumb->sr1 = sr1;
+        crumb->sr2 = sr2;
+    }
+}
+
+enum {
+    IRQ_ENTRY           = 1,
+    TXE_ONLY            = 2,
+    TXE_BTF             = 3,
+    STOP_SENT           = 4,
+    TEST                = 5,
+    RX_ADDR_START       = 6,
+    RX_ADDR_STOP        = 7,
+    RXNE_ONLY           = 8,
+    RXNE_SENDING        = 9,
+    RXNE_START_SENT     = 10,
+    RXNE_STOP_SENT      = 11,
+    RXNE_DONE           = 12,
+};
+
+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;
+    leave_big_crumb(IRQ_ENTRY, sr1, sr2);
+
+    /*
+     * EV5: Start condition sent
+     */
+    if (sr1 & I2C_SR1_SB) {
+        msg->xferred = 0;
+        i2c_enable_irq(dev->regs, I2C_IRQ_BUFFER);
+
+        /*
+         * Master receiver
+         */
+        if (read) {
+            i2c_enable_ack(dev->regs);
+        }
+        i2c_send_slave_addr(dev->regs, 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->regs);
+                dev->msgs_left--;
+                if (dev->msgs_left) {
+                    i2c_start_condition(dev->regs);
+                    leave_big_crumb(RX_ADDR_START, 0, 0);
+                } else {
+                    i2c_stop_condition(dev->regs);
+                    leave_big_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.
+             */
+            i2c_write(dev->regs, 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)) {
+        leave_big_crumb(TXE_ONLY, 0, 0);
+        if (dev->msgs_left) {
+            i2c_write(dev->regs, 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->regs, 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)) {
+        leave_big_crumb(TXE_BTF, 0, 0);
+        if (dev->msgs_left) {
+            leave_big_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 fuck ST?
+             */
+            i2c_start_condition(dev->regs);
+            while (!(dev->regs->SR1 & I2C_SR1_SB))
+                ;
+            dev->msg++;
+        } else {
+            i2c_stop_condition(dev->regs);
+            /*
+             * 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->regs, I2C_IRQ_EVENT);
+            leave_big_crumb(STOP_SENT, 0, 0);
+            dev->state = I2C_STATE_XFER_DONE;
+        }
+        sr1 = sr2 = 0;
+    }
+
+    /*
+     * EV7: Master Receiver
+     */
+    if (sr1 & I2C_SR1_RXNE) {
+        leave_big_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->regs);
+            if (dev->msgs_left > 2) {
+                i2c_start_condition(dev->regs);
+                leave_big_crumb(RXNE_START_SENT, 0, 0);
+            } else {
+                i2c_stop_condition(dev->regs);
+                leave_big_crumb(RXNE_STOP_SENT, 0, 0);
+            }
+        } else if (msg->xferred == msg->length) {
+            dev->msgs_left--;
+            if (dev->msgs_left == 0) {
+                /*
+                 * We're done.
+                 */
+                leave_big_crumb(RXNE_DONE, 0, 0);
+                dev->state = I2C_STATE_XFER_DONE;
+            } else {
+                dev->msg++;
+            }
+        }
+    }
+}
+
+void I2C1_EV_IRQHandler(void) {
+   i2c_dev *dev = I2C1;
+   i2c_irq_handler(dev);
+}
+
+static void i2c_bus_reset(i2c_dev *dev) {
+    /* Release both lines */
+    gpio_write_bit(dev->gpio_port, dev->scl_pin, 1);
+    gpio_write_bit(dev->gpio_port, dev->sda_pin, 1);
+    gpio_set_mode(dev->gpio_port, dev->scl_pin, GPIO_MODE_OUTPUT_OD);
+    gpio_set_mode(dev->gpio_port, dev->sda_pin, GPIO_MODE_OUTPUT_OD);
+
+    /*
+     * Make sure the bus is free by clocking it until any slaves release the
+     * bus.
+     */
+    while (!gpio_read_bit(dev->gpio_port, dev->sda_pin)) {
+        /* Wait for any clock stretching to finish */
+        while (!gpio_read_bit(dev->gpio_port, dev->scl_pin))
+            ;
+        delay_us(10);
+
+        /* Pull low */
+        gpio_write_bit(dev->gpio_port, dev->scl_pin, 0);
+        delay_us(10);
+
+        /* Release high again */
+        gpio_write_bit(dev->gpio_port, dev->scl_pin, 1);
+        delay_us(10);
+    }
+
+    /* Generate start then stop condition */
+    gpio_write_bit(dev->gpio_port, dev->sda_pin, 0);
+    delay_us(10);
+    gpio_write_bit(dev->gpio_port, dev->scl_pin, 0);
+    delay_us(10);
+    gpio_write_bit(dev->gpio_port, dev->scl_pin, 1);
+    delay_us(10);
+    gpio_write_bit(dev->gpio_port, dev->sda_pin, 1);
+}
+
+/**
+ * @brief Initialize an i2c device as bus master
+ * @param device to enable
+ * @param flags bitwise or of the following I2C options:
+ *      I2C_FAST_MODE: 400 khz operation
+ *      I2C_10BIT_ADDRESSING: Enable 10-bit addressing
+ */
+void i2c_master_enable(i2c_dev *dev, uint32 flags) {
+#define STANDARD_CCR           (PCLK1/(100000*2))
+#define STANDARD_TRISE         37
+    /* Reset the bus. Clock out any hung slaves. */
+    i2c_bus_reset(dev);
+
+    /* Turn on clock and set GPIO modes */
+    rcc_reset_dev(dev->clk_line);
+    rcc_clk_enable(dev->clk_line);
+    gpio_set_mode(dev->gpio_port, dev->sda_pin, GPIO_MODE_AF_OUTPUT_OD);
+    gpio_set_mode(dev->gpio_port, dev->scl_pin, GPIO_MODE_AF_OUTPUT_OD);
+
+    /* I2C1 and I2C2 are fed from APB1, clocked at 36MHz */
+    i2c_set_input_clk(dev->regs, 36);
+
+    /* 100 khz only for now */
+    i2c_set_clk_control(dev->regs, STANDARD_CCR);
+
+    /*
+     * Set scl rise time, standard mode for now.
+     * Max rise time in standard mode: 1000 ns
+     * Max rise time in fast mode: 300ns
+     */
+    i2c_set_trise(dev->regs, STANDARD_TRISE);
+
+    /* Enable event and buffer interrupts */
+    nvic_irq_enable(dev->ev_nvic_line);
+    i2c_enable_irq(dev->regs, I2C_IRQ_EVENT | I2C_IRQ_BUFFER);
+
+    /*
+     * 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);
+
+    /* Make it go! */
+    i2c_peripheral_enable(dev->regs);
+}
+
+
+int32 i2c_master_xfer(i2c_dev *dev, i2c_msg *msgs, uint16 num) {
+    int32 rc;
+    static int times = 0;
+
+    dev->msg = msgs;
+    dev->msgs_left = num;
+
+    memset(crumbs, 0, sizeof crumbs);
+
+    dev->regs->CR2 |= I2C_CR2_ITEVTEN;
+
+    /* Is this necessary? */
+    while (dev->regs->SR2 & I2C_SR2_BUSY)
+        ;
+
+    dev->state = I2C_STATE_BUSY;
+
+    i2c_start_condition(dev->regs);
+    rc = wait_for_state_change(dev, I2C_STATE_XFER_DONE);
+    if (rc < 0) {
+        goto out;
+    }
+
+    dev->state = I2C_STATE_IDLE;
+    rc = num;
+out:
+    return rc;
+}
+
+static inline int32 wait_for_state_change(i2c_dev *dev, i2c_state state) {
+    int32 rc;
+    i2c_state tmp;
+
+    while (1) {
+        tmp = dev->state;
+        if ((tmp == state) || (tmp == I2C_STATE_ERROR)) {
+            return (tmp == I2C_STATE_ERROR) ? -1 : 0;
+        }
+    }
+}
+
+
+/*
+ * Low level register twiddling functions
+ */
+
+/**
+ * @brief turn on an i2c peripheral
+ * @param map i2c peripheral register base
+ */
+void i2c_peripheral_enable(i2c_reg_map *regs) {
+    regs->CR1 |= I2C_CR1_PE;
+}
+
+/**
+ * @brief turn off an i2c peripheral
+ * @param map i2c peripheral register base
+ */
+void i2c_peripheral_disable(i2c_reg_map *regs) {
+    regs->CR1 &= ~I2C_CR1_PE;
+}
+
+/**
+ * @brief Set input clock frequency, in mhz
+ * @param device to configure
+ * @param freq frequency in megahertz (2-36)
+ */
+void i2c_set_input_clk(i2c_reg_map *regs, uint32 freq) {
+    uint32 cr2 = regs->CR2;
+    cr2 &= ~I2C_CR2_FREQ;
+    cr2 |= freq;
+    regs->CR2 = freq;
+}
+
+void i2c_set_clk_control(i2c_reg_map *regs, uint32 val) {
+    uint32 ccr = regs->CCR;
+    ccr &= ~I2C_CCR_CCR;
+    ccr |= val;
+    regs->CCR = ccr;
+}
+
+void i2c_set_fast_mode(i2c_reg_map *regs) {
+    regs->CCR |= I2C_CCR_FS;
+}
+
+void i2c_set_standard_mode(i2c_reg_map *regs) {
+    regs->CCR &= ~I2C_CCR_FS;
+}
+
+/**
+ * @brief Set SCL rise time
+ * @param
+ */
+
+void i2c_set_trise(i2c_reg_map *regs, uint32 trise) {
+    regs->TRISE = trise;
+}
+
+void i2c_start_condition(i2c_reg_map *regs) {
+    regs->CR1 |= I2C_CR1_START;
+}
+
+void i2c_stop_condition(i2c_reg_map *regs) {
+    regs->CR1 |= I2C_CR1_STOP;
+}
+
+void i2c_send_slave_addr(i2c_reg_map *regs, uint32 addr, uint32 rw) {
+    regs->DR = (addr << 1) | rw;
+}
+
+void i2c_enable_irq(i2c_reg_map *regs, uint32 irqs) {
+    regs->CR2 |= irqs;
+}
+
+void i2c_disable_irq(i2c_reg_map *regs, uint32 irqs) {
+    regs->CR2 &= ~irqs;
+}
+
+void i2c_enable_ack(i2c_reg_map *regs) {
+    regs->CR1 |= I2C_CR1_ACK;
+}
+
+void i2c_disable_ack(i2c_reg_map *regs) {
+    regs->CR1 &= ~I2C_CR1_ACK;
+}
+
+
+